A COMPREHENSIVE INVESTIGATION OF LEAD SHEATHING FROM THE EMANUEL
POINT SHIPWRECKS IN PENSACOLA BAY, FLORIDA
by
Andrew Wallace Marr
B.A., Colorado State University, 2006
A thesis submitted to the Department of Anthropology College of Arts and Sciences The University of West Florida In partial fulfillment of the requirements for the degree of Master of Arts
2012 The thesis of Andrew Wallace Marr is approved:
______Gregory D. Cook, M.A., Committee Member Date
______Amy Mitchell-Cook, Ph.D., Committee Member Date
______John E. Worth, Ph.D., Committee Member Date
______John R. Bratten, Ph.D., Committee Chair Date
Accepted for the Department/Division:
______John R. Bratten, Ph.D., Chair Date
Accepted for the University:
______Richard S. Podemski, Ph.D., Dean, Graduate Studies Date
ACKNOWLEDGMENTS
This study would never have been possible without the contributions and support of a number of different organizations and individuals. Many facets of my research involved scientific analysis, and I would like to thank Dr. Elizabeth Benchley and the UWF Archaeology
Institute, as well as the Pensacola Archaeological Society for their financial support. Without their grants and funding much of this thesis would have gone unwritten.
I am very appreciative to my committee for their efforts throughout the course of this study, from helping me to plan the excavations and experimentation to tirelessly editing draft after draft of each of my chapters. I would also like to thank a number of friends and fellow students for their contributions to my research. These include Dr. Felipe Castro, Dr. Pam
Vaughn, Chuck Meade, Jake Shidner, Colleen Lynn Reese-Lawrence, Tim Holmes, Kad
Henderson, Sarah Linden, Wes Perrine, Allen Wilson, Marisa Foster, Erica Smith, Matt Gifford,
Wayne Abrahamson, Patrick Johnson, and Cindi Jackson.
I must also thank Dr. George Kamenov at the University of Florida for the use of his laboratory and his help in conducting, analyzing, and interpreting the results of the lead isotope analysis. His constant support and unwavering dedication to my study, not to mention his patience, truly brought my research together. I would also like to thank Dr. Ignacio Montero
Ruiz at the University of Seville for allowing me to use his comparative isotope database, with which I was able to determine the sheathing’s original provenience.
I must of course thank my loving and supportive parents and sister, who taught me the virtues of dedication, hard work, and stick-to-it-iveness. For all the unquestioning understanding, the positive reinforcement, the unwavering support, and the hundreds of encouraging phone calls, I truly and sincerely thank you. In addition, I must make mention of my father’s
iii unsurpassed obsession with small, old-fashioned Italian hardware stores, without which I never would have been able to construct my experimental model.
Lastly, but certainly not least, I would like to thank my wife Crystal, whose love, support, patience, and constant encouragement has helped me throughout the course of my research. Her unbelievable dedication and ceaseless reassurance gave me the drive to finish what I started, and for that I will be forever grateful.
iv
TABLE OF CONTENTS
ACKNOWLEDGMENTS ...... iii
LIST OF TABLES ...... vii
LIST OF FIGURES ...... viii
ABSTRACT ...... x
CHAPTER I. A COMPREHENSIVE EXAMINATION OF LEAD SHEATHING: AN INTRODUCTION ...... 1 A. Background on the Luna Expedition ...... 4 B. Identifying the Wrecks ...... 6
CHAPTER II. DEVELOPMENT, IMPLEMENTATION, AND EVOLUTION...... 9 A. Ancient Implementation ...... 11 B. Sheathing in the Middle Ages ...... 14 C. Lead-Based Sheathing ...... 16
CHAPTER III. EXCAVATIONS ...... 23 A. Archaeological Excavations of Emanuel Point I and II ...... 24 B. Site Formation Processes ...... 27 C. 2010 Field Research: Motives and Background ...... 28 D. 2010 Field Research: Excavations ...... 30
CHAPTER IV. ARTIFACT ANALYSIS ...... 34 A. Sheathing Strips ...... 35 B. Square Patches ...... 39 C. Sheathing Tacks ...... 43 D. Implications and Assessments ...... 46 E. Summary…… ...... 49
CHAPTER V. EXPERIMENTAL ARCHAEOLOGY ...... 52 A. Sheathing Experiment Goals ...... 55 B. Construction and Design ...... 58 C. Deconstruction and Observations ...... 64 D. Tack Analysis ...... 68
CHAPTER VI. A HISTORY OF LEAD MINING AND THE APPLICATION OF LEAD ISOTOPE ANALYSIS ...... 73 A. Lead Mining in the Ancient World ...... 73 B. The Rebirth of Spanish Mines ...... 77
v
C. Lead Isotope Analysis: Background ...... 82 D. Technological Development ...... 85 E. Sample Preparation ...... 88 F. Data Analysis and Comparison ...... 93
CHAPTER VII. SUMMARY AND CONCLUSIONS ...... 110
REFERENCES ...... 115
APPENDIXES ...... 126 A. Tack Weights and Measurements for Sheathing Experiment ...... 127 B. XRF Analysis of Lead Sheathing Samples ...... 134 C. MC-ICPMS Results of Lead Sheathing Isotope Analysis ...... 137 D. Ossa Morena Zone and Los Pedroches Comparative Data ...... 140
vi
LIST OF TABLES
1. Average Values Of Lead Sheathing And Mina La Sultana Isotope Ratios ...... 106
vii
LIST OF FIGURES
1. Strip of lead sheathing ...... 36
2. Tack head impressions ...... 37
3. Sheathing patch with eight tack head impressions ...... 40
4. Epoxy cast replica of a sheathing tack ...... 44
5. Construction of the models with overlapping strips of lead ...... 60
6. Model with arbitrarily spaced tacks placed over strips of lead ...... 60
7. Model One with complete sheathing ...... 62
8. Model Two with partial sheathing ...... 62
9. Model Two after one month of submersion ...... 64
10. Model One immediately after removal from Emanuel Point II ballast pile ...... 65
11. Model Two immediately after removal from Sabine Island docks ...... 65
12. Teredo damage on exposed sections of Model One ...... 67
13. Model Two showing no teredo boreholes under formerly sheathed section ...... 67
14. Internal teredo damage on corner of Model One ...... 68
15. The Multiple Collector-Inductively Coupled Plasma Mass Spectrometer at the University of Florida ...... 93
16. Scatter plot of lead isotope data for sheathing samples using radiogenic and primeval ratios ...... 97
17. Scatter plot of lead isotope data for sheathing samples using radiogenic ratios ...... 97
18. Radiogenic and primeval ratio scatter plot of lead sheathing and Ossa Morena Zone ...... 100
19. Radiogenic ratio scatter plot of lead sheathing and Ossa Morena Zone ...... 100
20. Radiogenic and primeval ratio scatter plot of lead sheathing and Ossa Morena Zone (scale adjusted for comparative analysis) ...... 101
viii
21. Radiogenic ratio scatter plot of lead sheathing and Ossa Morena Zone (scale adjusted for comparative analysis)...... 101
22. Radiogenic and primeval ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region ...... 104
23. Radiogenic ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region ...... 104
24. Radiogenic and primeval ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region (scale adjusted for comparative analysis) ...... 105
25. Radiogenic ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region (scale adjusted for comparative analysis) ...... 105
26. Locations of Mina La Sultana in relation to known ore deposits of southern Spain ...... 108
ix
ABSTRACT
A COMPREHENSIVE EXAMINATION OF LEAD SHEATHING FROM THE EMANUEL POINT SHIPWRECKS IN PENSACOLA BAY, FLORIDA
Andrew Wallace Marr
Samples of lead sheathing recovered from the Emanuel Point wrecks, two sixteenth- century colonial Iberian vessels, underwent a series of analytical methodologies to determine the lead’s original provenience. Historical evidence suggested, but did not confirm, the probability that the lead used to protect these vessels originally came from Spain. Prior to this thesis, it was theorized that a New World source of lead may have provided colonial vessels with replacement sheathing, had they required such repairs. Experimental archaeology, x-ray fluorescence, and multiple-collector inductively coupled plasma mass spectrometry confirmed that the lead originated from a mine known as Mina La Sultana located in southern Iberia, and that this sheathing technique could survive the duration of a transatlantic voyage.
x
CHAPTER I
A COMPREHENSIVE EXAMINATION OF LEAD SHEATHING: AN INTRODUCTION
Lead sheathing was integral to Iberian expansion in the fifteenth and sixteenth centuries, as it protected wooden vessels from the multitudes of teredo worms breeding in warmer
Caribbean waters. It also functioned as a barrier for any leaks permeating ships’ seams and provided a measure of security against any damaged areas on their outer hulls. The practice of protecting a ship’s hull in lead lasted for centuries, and while not the most visible aspect of ship design, lead sheathing was nevertheless a necessity on any transatlantic voyage.
Almost every recorded Spanish shipwreck from the 16th century contains some amount of lead sheathing, regardless of whether the vessel was associated with colonialism, exploration, or transportation. Yet despite its necessity and widespread usage, little documentation exists on the subject of lead hull protection. Very few written sources discuss it in any length, and those that do provide only brief descriptions, compared to the more effective and better documented practice of sheathing ships in copper alloy during later periods.
This thesis aims to provide an in-depth examination of lead hull sheathing, specifically that from the two Emanuel Point wrecks (8ES1980 and 8ES3345) in Pensacola Bay. Originally part of an eleven-ship fleet, the two Emanuel Point wrecks are all that remain of a failed attempt to establish a Spanish settlement in North America (Smith et al. 1998). Over one and a half thousand settlers sailed into Bahia Santa Maria de Ochuse, or modern day Pensacola Bay, on
August 15, 1559, ready to establish a permanent settlement. On September 19, however, only weeks after their arrival, a devastating hurricane struck and decimated Spanish ships and supplies. What was originally a colonization attempt became a desperate struggle for survival,
1 and the colonists salvaged as much as they could from what was left of their fleet now scattered across the bay (Priestly 1928:245; Priestly 1936:109).
The wrecks gradually deteriorated and remained untouched for over four hundred years prior to the discovery of the first vessel in 1992 (Smith et al. 1998). While this study focuses exclusively on the lead artifacts recovered from these Emanuel Point wrecks, the analytical methods and resulting data potentially apply to any lead-clad vessels contemporaneous to these two ships.
This study investigates three main questions, each of which examines a particular aspect of lead sheathing. These are (a) to what extent did the sheathing cover the hulls of these vessels,
(b) could the sheathing last the length of a transatlantic voyage, and (c) did the lead originate in the Old World or the New? Each section of this thesis is an independent study aimed at answering these questions, and each conclusion provides a basis from which the following section develops. Ultimately, this work is a narrative, one that attempts to reveal as many characteristics of a single artifact as possible.
The first section combines history and maritime archaeology, beginning in Chapter II, with an examination of sheathing techniques throughout the ages. This chapter provides an evolutionary perspective on the technological advancement of hull protection, ultimately leading to the application of lead. Chapter III describes the excavation methods used to retrieve pieces of lead from around both wrecks and the decision to search for possible sheathing still nailed to the ships’ hulls.
The second section covers artifact analysis, and in Chapter IV an in depth examination of recovered lead strips provides an understanding of application methods that are difficult to determine through onsite examinations alone. This revelation leads to the question of sheathing’s
2 longevity, specifically how long lead sheathing remained attached to a ship’s hull. Chapter V attempts to answer this question with experimental archaeology through the submersion of two replicas of hull sheathing in Pensacola Bay. Constant monitoring of these replicas reveals a distinct pattern of corrosion, which in turn allows for the establishment of a timeline of deterioration. Though it is impossible to determine exactly how long it would take before lead sheathing loosened and fell free from a ship’s hull, this experiment attempts to answer that question scientifically by observing the rate of galvanic corrosion. The final results help in establishing whether lead applied in Spain could withstand a transatlantic journey and still remain intact once the vessel arrived in a colonial port in New Spain.
The results of this experiment are the basis for the final section of this study, explained in
Chapter VI and summarized in Chapter VII. This section attempts to determine the earliest provenience of the lead, employing lead isotope analysis to establish a point of origin. While
Chapter V revealed whether the lead would indeed last the journey across the Atlantic, Chapter
VI takes this a step further and asks whether the lead was originally mined in Spain or resheathed in Vera Cruz using metal mined in the New World.
This work employs a number of analytical methodologies, from experimental archaeology, to underwater excavation, to X-ray fluorescence, and finally lead isotope analysis.
Every section utilizes a variety of different sources from the historic to the scientific, all of which add to the legitimacy of arguments made within each chapter. This study also incorporates archaeological data from “peer” shipwrecks, believed to be contemporaneous to the Emanuel
Point vessels and associated with New World Spanish colonialism (Brinkbaumer et al. 2006,
Castro 2003; Crisman 1999; Lyon 1985; Monteiro and Garcia 1998; Morison 1942). These
3 vessels also possess lead sheathing in various capacities and provide examples from which to draw comparable information.
Were one to summarize this work in only a few words, it would be considered a study on provenience, as the progression of data from the previous chapters eventually culminate in the final section, wherein a point of origin is established for the lead. However, as mentioned earlier, each section of this thesis is an independent study on its own and, despite the gradual progression of information that eventually aides in the final analysis, every aspect of this study provides its own unique perspective on lead sheathing. This thesis is essentially an exploration of a single artifact, one that attempts to establish a better understanding of an often-overlooked aspect of
Iberian ship construction.
Background on the Luna Expedition
Spanish explorers first identified Bahia Santa Maria de Ochuse as a potential colony as early as 1539 (Weddle 1985:217-218). Exploratory scouts, sent to identify potentially inhabitable harbors, claimed that Ochuse offered the best protection and port of access to La Florida
(Priestly 1928, vol. 1:xxi, xxvii, xxxv). Deep waters and a defensive entrance made this bay an ideal location for a permanent settlement.
The colonization of Ochuse, or modern day Pensacola, was to precede a second colony, located in modern day South Carolina. These two settlements would provide a safe means for vessels to transport their cargos to and from Spain and in so doing prevent them from having to navigate the treacherous waters around the Florida Keys (Velasco 1559b:225). Luis de Velasco,
Viceroy of New Spain, planned and directed the expeditions after receiving permission and partial funding from King Phillip II of Spain (Cook et al. 2008:66; Velasco 1558:257-259).
4
A list of financial records located in the Archivo General de Indias in Seville, Spain, known as Contaduria 877, provides a catalogue of provisions supplied to the vessels prior to their departure. Compiled by the deputy treasurer in Veracruz from March 1554 to January 1559, these records itemize in detail the exact size, weight, portions, and cost of every item taken aboard each of the eleven ships. While the majority of the provisions fall under the category of foodstuffs, artillery, or rigging, the occasional reference to lead, or plomo, does appear:
The said Pedro de Yebra presented the account for 15 pesos of common gold that
he gave and paid to Juan de Sena for 15 arrobas [around twenty-five pounds] of
lead which was purchased from him for the voyage that the said Angel de
Villafana made to Florida, at 1 peso per arroba (Childers 1999:127).
Unfortunately, Contaduria 877 does not specify the intended purpose of the lead, or whether, in this case, Pedro de Yebra purchased it specifically for ship repairs or for some other utilitarian purpose. The reality, however, is that these vessels were intended to be used for the duration of this colonization attempt, and presumably a few were meant to stay with the colonists after a settlement had been established. The ships would inevitably require a number of repairs over time, one of which was maintaining the lead sheathing nailed to their outer hulls.
The fleet consisted of eleven ships. Eight were previously owned, and three were built specifically for this voyage in Mexico. The fleet departed in June of 1559 from the port of San
Juan de Ulua in Vera Cruz led by conquistador Tristán de Luna y Arellano and spent three months crossing the Caribbean (Worth 2009:83). The fleet made two stops prior to arriving in
Ochuse: once for water and provisions just east of their destination and again at what is now
Mobile, due to problematic navigation (Weddle 1985:267). The colonists finally arrived at their
5 destination on August 15, 1559, and immediately began unloading livestock and supplies. They left most of their food and provisions on board, however, to protect them from natives and wild animals. Unfortunately, this decision, while a sensible solution to their problem, would inevitably prove fatal.
Prior to the colonists’ arrival, reconnaissance missions to Ochuse mistakenly stated that the bay was “so secure that no wind can do them [ships] any damage at all” (Velasco
1559a:275). Yet on September 19, only weeks after their arrival, a hurricane made landfall in the vicinity of Ochuse, decimating seven of the ships still anchored in the bay (Luna y Arellano
1559:245, Priestly 1928, vol. 1:xxxv). The hurricane sank six of the vessels, tossing a seventh ship inland. Having already sent one ship back to Vera Cruz to spread word of the mission’s success, Luna possessed only three working vessels after the storm.
Many sources mention the subsequent struggle for survival endured by the colonists over the next two years (Hudson et. al 1989:39-45; Weddle 1985:268-281), though little of that record proves relevant for this study. Needless to say, the colonists did attempt to salvage as much as they could from the wrecks that remained, using divers to retrieve what supplies laid scattered along the bay floor (Velasco 1559c:79).
Identifying the Wrecks
Today, archaeologists know the location of two of the six ships still buried in Pensacola
Bay. While initial investigations and artifact assemblages identified these wrecks as belonging to the Luna fleet, the specific names of these vessels remained unknown for years. However, recent attempts to identify the wrecks using archeological data on hull structure, as well as various historical accounts, have presented researchers with likely candidates (Worth 2009; Collis 2008).
In his letter to King Phillip II, Tristan de Luna mentions that the vice flagship of his fleet, a
6 galleon known as the San Juan de Ulua, sank in the storm (Collis 2008:45-46). The first discovered wreck, Emanuel Point I, seems to fit the description of this vessel remarkably well, as the San Juan was a well-built, larger military vessel with significant reinforcement along its inner hull (Phillips 1986:19). Archaeological evidence suggests that Emanuel Point I does indeed possess a well-braced hull, and its overall size corresponds to that of a larger vessel such as a galleon (Smith et al. 1999:63).
Emanuel Point II is smaller than Emanuel Point I, which suggests that it was one of three smaller vessels also lost in the storm: the Santa Maria de Ayuda, the Sancti Espiritu (or Espirito
Santo), or the San Amaro (Worth 2009:87-88). These vessels belonged to a category of ships known as naos or navios, a term used for ships with full-rigging and primarily used for cargo transportation (Pérez-Mallaína 1998:227). Unfortunately, due to the similarities of all three candidates, it is difficult to pinpoint exactly which of these three vessels is Emanuel Point II.
It is important to note that none of the potential candidates for either Emanuel Point I or
II originated in Veracruz (Cook et al. 2008:72). Construction of these vessels occurred elsewhere, most likely Spain, and they visited many other ports prior to their use as colonial vessels (Worth 2009:87-88). These ships possess a history that extends far beyond that of the
Luna expedition and, unfortunately, little documentation exists to reveal what that history might be.
This study attempts to fill in a small piece of that missing history and to provide a resource from which future researchers may do the same. Although it is little more than a footnote in the overall history of these vessels, the application of sheathing was nonetheless a crucial part of the preparatory process of any voyage. By examining the method of its
7 application, its longevity once applied, and its point of extraction prior to its use in port, this study may provide a unique perspective on the provisioning and maintenance of Iberian ships.
8
CHAPTER II
DEVELOPMENT, IMPLEMENTATION, AND EVOLUTION
Since the dawn of seafaring, human beings have employed an astonishing array of techniques to protect their watercraft from harm. Over the past few millennia, mariners have attempted to protect wooden vessels with almost every item imaginable, including wood, lead, zinc, tin, copper, porcelain, clay, reeds, paper, papyrus, vegetable fabrics, glass, Indian rubber,
Roman cement, Greek cement, leather, sulfur, animal fats, chain-mail, bone marrow, guano, and paints (Young 1867:36; Lemnius 1575). Over time, as watercraft continued to evolve, the need for sheathing remained constant.
As civilizations developed more sophisticated means of navigation, sailors ventured out to the farthest corners of the earth for trade, colonization, and exploration. Starting in the fifteenth and sixteenth centuries, European explorers took particular advantage of their navigational and technological superiority and set out to conquer most of the world by sea. It was during these voyages in warmer American and Asian waters that they encountered veritable hordes of Teredo Navalis, a seaborne parasite that feeds on the cellulose in wood (Stephens
1952). The warmer waters of the Caribbean and Florida were home to far greater numbers of teredo than ever before seen in Europe (Jones 2004:77).
Teredo Navalis is a mollusk, comprised of a tiny hard shell and an elongated body that can reach up to 60 cm in length (Hoppe 2002:116). Mistakenly called a worm due to its worm- like appearance, the teredo is more closely related to the oyster and mussel; however, the names
“teredo worm” or “ship-worm” are commonly used monikers and are acceptable in academic dialogue (Hoppe 2002:116). Teredo worms live as microscopic spores in their larval state, dispersed in saltwater like plankton or krill. As larvae, their bodies are round and clear, with
9 hundreds of string-like feelers, or cilia, covering their surface (Cohen and Carlton 1995). A hard shell on one end of their bodies denotes where their “heads” are located (Cohen and Carlton
1995).
They are instinctively attracted to wood cellulose, utilizing their tiny cilia to swim closer to wooden objects as they pass by (Hoppe 2002:116); in this case, ships’ hulls. The parasitic larvae latch onto ships with a tendril called a byssus thread, excreting an acidic enzyme through this thread that dissolves a tiny spot of wood (Clapp 1967:192). Boring into the wood with sharp, shelled heads, they slowly digest the sugar molecules in the cellulose (Hoppe 2002:116). As the teredo continues to drill, its body grows in length and girth. A calcareous excretion released from the mollusks’ glands creates a hard casing that lines the tunnel of the teredo’s borehole as it continues to feed (Cohen and Carlton 1995; Hoppe 2002:116-117). The teredo then emits a tiny tendril, or “siphon,” from its rear end and leaves it hanging out from the original borehole
(Cohen and Carlton 1995; Hoppe 2002:116-117). Exposed to the elements, this allows the teredo to detect the conditions of the external environment, as well as siphon oxygen and plankton from the water (Cohen and Carlton 1995). When exposed to direct air or fresh water, the teredo can seal off its tunnel, leaving its siphon exposed, until conditions become more favorable (Hoppe
2002:117). The mollusk can live up to a month without oxygen or saltwater (Hoppe 2002:117), making it extremely difficult to kill even when a vessel remains careened for weeks at a time.
A teredo worm never emerges from its wooden habitat. While other marine borers require more variety in their diets, Teredo Navalis is capable of living exclusively on cellulose (Clapp
1967:192-193). Before mass oceanic travel, teredo lived in warmer waters latching onto debris and the occasional canoe or barge. Larger ships and an increase in transoceanic travel spread the
10 parasite across the world, making the teredo worm a serious problem for almost every seafaring nation (Clapp 1967:193).
Understanding the technological evolution of anti-fouling and waterproofing measures prior to the use of lead helps to develop an appreciation for sixteenth-century Iberian lead sheathing. Fortunately, for analytical purposes, sheathing underwent distinct changes throughout the course of naval history. Using a combination of historical and archaeological research one can piece together a rough evolutionary history.
Ancient Implementation
The term fouling pertains to all sea-life that attaches itself to the sides of wooden vessels
(Stephens 1952:17). Algae, barnacles, and plants all fall under this category. Fouling, while not as invasive as teredo worms, eventually wears down the integrity of a wooden hull and adds a significant amount of drag (Lemnius 1575). While few written records exist from the earliest attempts at shipbuilding (Schuster 2000), inevitably the presence of barnacles and leaking hulls has always been a major concern.
While more recent methods of hull protection have attempted to stop teredo worms, sheathing in the ancient world aimed at waterproofing vessels and protecting them from fouling
(Hocker 1985:197). This was in part due to the scarcity of teredo in European waters, which was never a serious problem before transatlantic exploration (Hocker 1985:198).
In the fourth century BC, Aristotle theorized that a ship’s speed gradually decreased over time due to the remora, a fish he nicknamed “the ship stopper” (Plutarch 1898). Later scholars determined that this decrease in speed was not, in fact, due to a group of fish attaching themselves to the bottom of the vessel, but rather to a buildup of marine life accumulating on the hull (Lemnius 1575). As a solution, Greek sailors designed a type of long, curved rake which
11 allowed them to clean their vessels at sea (Lemnius 1575). A Greek scholar of ancient maritime history, Laevinus Lemnius wrote about the speed with which fouling could occur to these ancient ships:
Shell-fish and a little fish called Echeneis stick so fast that they will stop ships,
and hinder their courses, therefore men used to rub them off with sharp brushes,
and scrape them away with irons that are crooked for the purpose, that the ship
being tallowed and careened well and smoothly may sail the faster (1575).
The Carthaginians and Phoenicians were among the first to use chemical agents on their ships, concoctions made from materials such as wax, tar, pine pitch, clay, and asphaltum1
(Masseille 1933:232). Many of these techniques, such as clay and asphaltum, suggest an attempt to waterproof the vessel, while methods involving wax suggest an intention to create a smoother and more streamlined outer hull, allowing the vessel to move with less drag (Neuberger
1930:518). In an effort to prevent rot and sun damage, Greek sailors rubbed a mixture of arsenic, sulfur, and oil onto their ships using hot irons while the vessel was in dry dock (Stephens
1952:212).
While never implemented in any large-scale capacity until centuries later, ancient sailors used flattened pieces of lead to repair and waterproof smaller vessels (Pérez-Mallaína 1998). The
Greeks experimented with lead as early as the third century BC, using copper tacks and fasteners to nail the lead in place (Culver 1928:54). In fact, one of the oldest examples of this technique comes from the Porticello wreck, a Roman vessel from the fifth century BC. Archaeological investigations recovered narrow strips of lead, each possessing a series of nail holes running along the sides (Hocker 1985:199).
1 A combination of tar, sand, and hair. 12
Lead’s malleability made it a versatile material for ship maintenance. Not only could a sailor hammer the metal to fit the lines of a ship, it possessed the ability to bend and flex with the expansions and contractions of a seagoing vessel without cracking (Hocker 1985:200). Due to the difficulties associated with extracting the metal, only the most dilapidated ships desperately in need of repair, or those belonging to royalty, obtained any significant amount of lead (Hocker
1985:200).
To create an impregnable watertight seal, sailors applied lead over fibrous materials such as resin-soaked palm fir, woven cloth, or animal hair (Rosen 2007:305). Placing this material between the sheets of metal and the ship’s wooden hull sealed gaps between planks and further hindered the progress of parasitic borers (Stephens 1952:212).
There is strong evidence to suggest that early sailors applied sheathing simply to extend the life of their vessels. In 1967, researchers excavated a Greek trading vessel from the fourth century BC, later named the Kyrenia shipwreck, off the coast of Cyprus (Steffy 1985).
Archaeologists identified lead sheathing still attached to the outer hull of the vessel. After analyzing the state of the structural timbers and outer planks, researchers determined that the vessel was, in fact, already extremely old and teredo-riddled when first sheathed with lead
(Hocker 1985:198). The most logical explanation was that the vessel had required extensive structural repairs, and patching it with lead rather than replacing most of the timbers was a far cheaper option (Hocker 1985:198). Kyrenia’s lead extended far above the ship’s waterline, possibly protecting the caulking placed between the planks at the highest part of the ship’s hull
(Steffy 1985).
While lead sheathing was the favorite material for sheathing for centuries, archaeological evidence suggests that its popularity died out quickly. Vessels dating back to the fourth and third
13 centuries BC possess lead sheathing but very few ships from the second century BC show any evidence of metallic sheathing at all (Mallet 1872:102). In fact, by the end of the first century
BC, metallic sheathing almost completely disappears from the archaeological record (Hocker
1985:201).
Technologically it is possible that shipwrights developed effective chemical and plant- based methods of protection. According to the Roman scholar Pliny the Elder, wax and pitch- based coatings waterproofed hulls and protected ship’s seams effectively in the first century BC
(1967:56). These treatments cost far less to create and required less effort to apply than metal
(Pliny 1967:56).
Sheathing in the Middle Ages
Centuries later, as European nations ventured out and explored new territory, teredo worms emerged as a serious threat (Brinkbaumer et al. 2006). Christopher Columbus experienced this problem first hand on his fourth and last voyage to the West Indies in 1503 when he abandoned his shipworm-riddled ship Vizcaina off the Jamaican coast (Morison 1942;
Brinkbaumer et al. 2006). A mid-fifteenth century report written by officers of King Henry VI details the teredo threat: “They have heard that in certain partes of the ocean a kind of wormes is bredde which many times pearseth and eateth through the strongest oake that is” (Chatterton
1914:47). Colonization efforts depended on a successful defensive measure against these organisms; consequently sailors began experimenting with a variety of techniques.
In the sixteenth and seventeenth centuries the three most commonly used methods for protecting ships’ hulls were charring, double planking, and applying lead sheets (Jones 2004:77).
Charring consisted of burning a ship’s external planking using red-hot irons (Woodman 1997:94-
95). Charring created a layer of charcoal that was sealed with tar or pine pitch once the wood
14 cooled (Woodman 1997:95). Shipwrights believed this method would deter teredo worms, as they would find the charcoal unappealing and difficult to digest (Hawkins 1622). Many actually considered charring the most successful form of protection ever invented, continuing to apply it to their vessels long after the resurgence of lead-based sheathing. In fact, in 1622 Admiral
Richard Hawkins, a noted British explorer and renowned scholar, claimed charring was still a common method of hull protection in the British Navy (1622:81).
However despite the popularity of charring, setting a wooden ship alight was never without its risks. A French technology journal made mention of this technique in 1666 stating,
“The Portugals scorch their ships, insomuch that in quick works there is made a coaly crust of about an inch thick. But as this is dangerous, it happening not seldom, that the vessel is burnt”
(Royal Society 1665:190).
Alternatively the technique known as double planking, or sacrificial planking, involved no burning but rather the application of thin sheets of wood over a ship’s outer hull (Hawkins
1622). William Petty of England, a seventeenth-century philosopher and scientist, wrote extensively on the topic of wooden sheathing:
First, that only component and allowable Defense against the Worm, before this
of Lead-Sheathing, was the paying of the hulls from the Water’s edge downwards
with Stuff, and laying inside of a Sheathing-Hair (from inch and quarter to three
quarters thick) all over with Tar and Graving or Paying the outside of the said
Board all over with another composition of Brimstone, Oyl, and other Ingredients,
which is called Wood-Sheathing [emphasis in original] (1691; 36-37).
“Sheathing-Hair” refers to animal hair, normally that of a horse or cow, which is supposedly indigestible to marine borers (Chatterton 1914). Mixed with tar, hair created an 15 impenetrable barrier that would stop Teredo worms from boring beyond the wood sheathing.
Richard Hawkins synonymously supported this method, claiming the best type of wood to use was elm, as it fit the contours of a ship better than pine, oak, or cedar (1622:81). Hawkins highly recommended wood sheathing for her Majesty’s royal fleet, as he believed it was cheap and effective at protecting ships hulls’ (1622:83).
Shipwrights applied the sacrificial layer of wood with copper or iron tacks, placing them in such close proximity to one another that the tack heads touched and formed a kind of metallic sheathing of their own (Fincham 1851: 94). Unfortunately, this added layer proved detrimental as the large, exposed heads caused significant drag at sea (Fincham 1851:94). In addition to impeding a ship’s movement, the iron heads also attracted marine growth as they corroded, eventually requiring maintenance and scraping so as to prevent fouling (Masseille 1933:232-
234). As the tacks rusted away, the underlying sheets of wood lost integrity, allowing teredo infested seawater to come into direct contact with the ship’s structure (Masseille 1933:233-234).
Lead-Based Sheathing
As shipwrights continued to adapt charring and double planking to suit their needs, many nations began to once again recognize the versatility of lead. While never utilized in any large scale capacity over the past thousand years, sailors had continued to use small quantities to repair damaged areas of ships’ outer hulls (Pérez-Mallaína 1998:23). Sixteenth-century Spanish ships had designated ‘divers,’ crewmembers whose job it was to swim under the hull while the ship was at sea, and repair breaches with hammered patches of lead (Pérez-Mallaína 1998:23). A diver’s task was imperative to the survival of the ship and her crew as the following 1551 account illustrates:
16
The said Pero Diaz stripped himself down to his skin and began to swim toward
the ship…and the said Pero Diaz searched underneath the water for the hole in the
said ship Pero Milantes…and he found it, and he stopped it up and nailed a sheet
of lead over it…Afterward he went to the ship of the said Luis Rizo, which was
also sinking, and he swam underneath the water, looked for the place where the
water was getting into the said ship, and found it in three or four places, and he
nailed his lead sheets so that he stopped the leaks (Pérez-Mallaína 1998; 73).
Due to technological limitations at the time, the fastest and most cost effective method of converting raw lead into sheets was by hammering them flat. Unfortunately this process produced fragile and unevenly weighted sheets of lead (Petty 1691). In the early sixteenth century a new system surpassed hammering in terms of efficiency, one that fashioned lighter, thinner sheets that seemed to maintain a consistent thickness (Jones 2004:34). Known as casting, this technique could potentially shape molten metal to any desired dimension by pouring it into shallow, flat molds. Unfortunately this new manufacturing method created sheets that were far too thin and delicate. While the lead would appear to harden as a level, flat cast, it cooled unevenly as it set in the mold (Petty 1691). Tiny microscopic cracks formed along the surface of the metal, widening over time, eventually allowing water and microscopic seaborne larvae to pass through. Richard Hawkins commented on its lack of durability and effectiveness after seeing it with his own eyes: “Some sheathe their shippes with lead; which besides the cost and weight, although they use the thinnest sheet-lead that I have seene in any place, yet it is nothing durable, but subject to many casualties” (1622: 81).
Hawkins believed that cast lead was far too ineffective and costly to justify its use and that its “many casualties” made it a poor shield from marine borers. Yet despite these flaws,
17 scholars and inventors recognized that the theory behind cast lead remained sound. The problem lay in developing a durable, light, thin sheet of metal capable of maintaining both flexibility and strength.
In 1670 British metalworkers Sir Philip Howard and Sir Francis Watson developed a manufacturing process known as milled lead. By casting lead into bars and passing them between two solid iron drums, they found they could roll a sheet of lead to any desired thickness.
The final lead sheet was dense, manufactured at an even thickness, and not prone to cracks as it never required cooling (Jones 2004:83). Howard and Watson applied for a patent shortly thereafter (Fincham 1851:96) writing that the patent was “For the sole use of the manufacture of milled lead for the sheathing of ships” (Petty 1691:5).
Thomas Hale, an employee of Watson and Howard’s Patent Milled Lead Company, stated that milled lead was twenty-two percent cheaper than cast lead and easier to apply than double planking or charring (1695). Milled lead did not require frequent cleaning or the constant reapplication of tar or resin between it and a ship’s outer hull (Hale 1695). It also reinforced the vessels and helped to keep the inner hull cool and dry (Jones 2004:83).
In 1670 the Royal Navy acknowledged the potential behind this invention and tested the milled lead on twenty ships, determining its effectiveness prior to widespread implementation
(Hay 1863:34). King Charles II inspected the vessels in 1673 after a six-month trial period.
Astonished at the lack of fouling and Teredo damage, he decreed, “no other than milled lead sheathing should be used on His Majesty’s ships” (Young 1867:40-42). In 1675 the Patent
Milled Lead Company received a twenty-year contract for the exclusive sheathing of all of
Britain’s naval fleet (Fincham 1851:75).
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Despite the King’s decree, not all naval officers believed lead to be the right choice.
Many found it cumbersome, heavy, and in some circumstances an impediment to the ship’s progress at sea. In 1668 Admiral Sir Thomas Allen petitioned that his fleet, tasked with attacking the Algerian coastline, not “be so encumbered [as they] were always unable to overtake the lightweight unsheathed vessels of the enemy” (Young 1867:47-49). The Royal Navy granted his petition on the stipulation that his entire fleet careen and clean their hulls as frequently as possible (Young 1867:49).
It soon became apparent that lead sheathing caused a far more serious problem than simply decreasing a ship’s speed. A number of reports from overseas told of a sudden and unexpected detriment to hull integrity (Mallet 1872:102). Sailors noted that after applying the lead sheathing, any iron attachments below the waterline rusted at a dramatically accelerated pace (Mallet 1872:102-103). These attachments included the gudgeons and pintles used for rudder attachment and bolts and fasteners that secured outer planks to frames. This accelerated corrosion resulted in structural damage and, in some extreme cases, the loss of rudders (Petty,
1691:8-11).
From Abroad, of a quality discovered in our lead sheathing, tending (if not timely
prevented) to the utter destruction of His Majesties Ships, namely
that of the Eating into, and wasting their Rudder-Irons and Bolts underwater, to
such a degree, and in so short a space of time, as had never been observed upon
any unsheathed or wood-sheathed ships [emphasis in original] (Petty 1691:9).
Subsequent investigations into the cause of this accelerated corrosion initially questioned the vessel’s record of maintenance. The HMS Dreadnought presented records of having replaced her rudder hardware only eighteen months earlier in 1676, the same year the vessel received an 19 allotment of lead sheathing (Petty, 1691:45). In 1678, only two years later, her crew claimed that her iron parts “were very much eaten and consumed, and not to be trusted at sea” (Petty,
1691:45). Sailors replaced Dreadnought’s iron attachments and four years later they appeared practically eaten through, held together with “merely rust and dirt” (Petty, 1691:45). The HMS
Plymouth and the HMS Phoenix, two of the original twenty ships covered in lead, suffered similar problems. Each vessel required replacement rudder hardware within two years of receiving lead sheathing, as most of the original iron fittings had already completely disintegrated (Mallet 1872:90-92).
While the specifics behind galvanic and electrochemical corrosion remained a mystery at the time, the admiralty understood that lead was to blame for the recent degradation of ship’s hardware (Petty 1691:25). This realization stemmed from the fact that the metal fittings on the vessels underwent accelerated corrosion only after applying the lead sheets. Fearing the king would blame poor seamanship and shoddy maintenance as the cause of the problems, the admiralty placed most of the blame on the Patent Milled Lead Company (Fincham 1851:94-95).
The naval court eventually decided to cease sheathing ships in lead until they could find a solution to the corrosion problem, and in the meantime search for a substitute material to take lead’s place. Despite repeated appeals from the Patent Milled Lead Company, the Royal Navy terminated their contract in 1691 (Hale 1695).
Over seventy years of trial and error occurred before the first implementation of copper sheathing in 1761 (Young 1867:49). Copper’s malleability and its toxicity to marine life made it a prized metal in shipyards and it quickly became the most effective type of wooden hull protection in history (Cross 1927:80). However, as was the case with lead, copper, and iron also resulted in accelerated corrosion. The advent of mixed alloys and sacrificial anodes, as well as a
20 more thorough understanding of galvanic corrosion, eventually eradicated such problems altogether.
While British inventors were the first to experiment with milled lead, Spain was the first to adopt hammered lead as its official form of sheathing after a sixteenth-century proclamation by Charles V (DiArtinano 1924:212). Unlike England, Spain implemented lead across the entire fleet, as the exploration and colonization of the New World employed a vast number of their ships that required immediate protection (Young 1867:50). Prior to Charles V’s proclamation,
Spanish vessels were “covered with a mixture of tallow and pitch in the hopes of discouraging barnacles and teredo’s” (Morison 1942:134).
Howard and Watson patented their milled lead in 1670; therefore, the sheathing used on the 1559 Luna fleet likely consisted of either hammered or cast lead. Artifacts from the Emanuel
Point wrecks indicate that these ships possessed strips of lead rather than sheets (Smith et al.
1998:60). Applying the lead in strips rather than panels or sheets was perhaps Spain’s solution to the fragility of cast lead, as smaller strips remained less susceptible to the constant stresses experienced by larger panels while at sea. Though many of the lead strips recovered from the
Emanuel Point wrecks have at least fifteen to twenty tacks holes on their surface, archaeologists have recovered very few of the tacks used to secure the lead to the side of the ship (Smith et al.
1998:20).
While not the most effective means of protecting a ship’s hull, lead’s implementation in the sixteenth and seventeenth centuries played a significant role in the advancement of science.
Contemporary scholars broadened their understanding of galvanic corrosion and electrolytic reduction and used whatever means possible to counter them despite technological limitations. In addition, mass production of lead sheathing directly resulted in the creation of rolling mills.
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Lead recovered from the Emanuel Point wrecks presents researchers with a distinct perspective on technology at this point in naval history; a point when the most basic of materials was given the enormous, untested task of preserving a ship’s hull. Many articles and first-hand accounts emphasize the problems associated with lead sheathing, yet it endured as a means of protection for centuries. This longevity implies a certain degree of functionality to lead sheathing, one that the Spanish trusted enough to transport hundreds of vessels across the
Atlantic Ocean and back again. However, sailors might have possessed a variety of motives for using lead, regardless of its effectiveness. It is unknown whether sailors used lead due to its cost, because it was plentiful, or because they lacked a better alternative. Nevertheless, the Emanuel
Point wrecks provide an insight into a culture that relied on lead sheathing during one of the longest and most significant periods of colonization and exploration in history.
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CHAPTER III
EXCAVATIONS
The Emanuel Point Shipwrecks currently rest at a relatively shallow depth of twelve to fifteen feet on a sandbar running just under a mile off shore in Pensacola Bay. Waters surrounding the wrecks lack clear visibility, though such difficulties drive researchers to adapt and perfect the art of low visibility investigations. Creating underwater illustrations and site plans is difficult in good visibility; without the ability to see it is considerably more challenging.
Nevertheless, over two decades’ worth of documentation on the Emanuel Point wrecks attest to the abilities of those who choose to excavate them.
Surrounded by sandy sediment, Emanuel Point I often has adequate visibility as the sand is too heavy to suspend in the water column (Smith et al. 1998:19). Alternatively, Emanuel Point
II, located a half mile closer to shore than Emanuel Point I, rests in loose, muddy sediment.
Strong currents constantly churn up the silty bay floor and the murky water creates poor visibility for divers.
Discovered fourteen years apart, researchers consider the Emanuel Point vessels to be two of the most important wreck sites located in Pensacola Bay (Smith et al. 1998:xii). Aside from the vessels’ historical significance, the discovery of the wrecks was major catalyst for the development of the underwater archaeology program at the University of West Florida (Smith et al. 1998: xiii, xiv). Unearthed at a time when Pensacola was gaining significant archaeological notoriety, the wrecks successfully helped push Pensacola into the spotlight and attracted the attention of various historical and archaeological societies as well as the media and the Spanish crown (Smith et al.1998:xiii).
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Archaeological Excavations of Emanuel Point I and II
In 1992 Roger Smith, a representative of the Florida Bureau of Archaeological Research and the state underwater archaeologist, conducted a statewide shipwreck survey along Florida’s coastline. The Pensacola Shipwreck Survey had the primary goal of conducting remote sensing operations to potentially locate colonial vessels from the first and second Spanish periods (Smith et al. 1998:15-16). A sandbar running along the Pensacola bay shoreline was theorized as a possible location for what remained of Tristán de Luna’s fleet. Poor weather and the shallow nature of the sand bar made initial attempts at obtaining acoustical data with side-scan sonar unsuccessful (however, more recent attempts have produced significantly better results).
Magnetometer surveys, however, presented researchers with far more viable data. In October of
1992 divers probed and visually inspected three of the final fifty-five magnetic anomalies located within the survey area (Smith et al. 1998:14). While the first two targets proved to be remnants of shrimp boat rigging and a metal cable, the third anomaly, registering at 400 gammas, revealed evidence of ballast stones. Subsequent excavations with an underwater metal detector revealed the remains of an anchor fluke, the source of the magnetic reading. Surveyors recognized the presence of a shipwreck and designated it 8ES1980.
Full-scale excavation soon began. In the summer of 1993 archaeologists from the Florida
Bureau of Archaeological Research and students from the University of West Florida surveyed the site using a metal detector, placing test units at various points both on and around the ballast pile (Smith et al. 1998:20). Excavators used hand fanning, hand collection, trowels, and water induction dredges to collect artifacts. Water induction dredges, essentially underwater vacuums, fed exhaust from the site to a floating barge above where artifacts and sediment passed through one-eighth-inch screen mesh (Smith et al. 1998:23). From 1993 to 1998 a combination of both
24 dredging and hand collection recovered 3,600 artifacts from Emanuel Point I (Scott-Ireton
1998:19-20; Smith et al. 1998:6, 29-30). More than 200 of these artifacts archaeologists identified as lead fragments.
The 1998 site report for Emanuel Point I encouraged additional survey work, concluding that “In the meantime, there are five or six other ships of the Tristán de Luna fleet at the bottom of Pensacola Bay waiting to be discovered” (Smith et al. 1998:171). As in the case of Emanuel
Point I, field school students located the second vessel by investigating specific anomalies identified though magnetometer surveys (Bratten et al. 2008:44). The presence of a ballast pile at a coinciding magnetic anomaly encouraged divers to excavate, leading to the discovery of hull timbers (Bratten et al. 2008:49). Test excavations began in 2006. Summer field schools of ten- week duration have been implemented from 2007 to present.
As of the summer of 2011 archaeologists placed forty-two units across the wreck site, covering approximately 25% of the ship’s exposed surface. Unlike the two-meter-square units on
Emanuel Point I, excavators opted for one-meter-square units as they conformed better to the smaller size of the ship and maintained uniformity throughout the excavation process.
As with the first vessel, hand fanning, hand collection, and water-induction dredges were the standard methods of excavation used on Emanuel Point II (Bratten et al. 2008). While the majority of these techniques remained the same, the water-induction system changed in order to increase the number of smaller artifacts and other specimens collected in the process.
Archaeologists on Emanuel Point I used a dredge system that channeled the exhaust to the surface, filtering it through a screen (Smith et al. 1998:23). Alternatively, students working on Emanuel Point II use a system where the exhaust remains submerged, resting on the bay floor, pumping the debris through a hose with a mesh bag attached at the end. Starting in 2008, field
25 school students began to double the mesh bags to collect smaller objects that might otherwise pass through the quarter-inch netting. The holes of the bags are nearly equivalent to screens used on Emanuel Point I, though they possess greater flexibility and tend to shift their alignment frequently. However, a barrier of debris eventually forms at the base of the bags, trapping smaller objects and preventing the loss of artifacts.
Aside from a few minor differences in artifact collection and unit size, the excavation methods conducted on Emanuel Point II mirror those of Emanuel Point I. Emanuel Point I contained several objects with a militaristic purpose including a breastplate, cannon balls, cast iron shot, lead-cased iron shot (bodoques), and crossbow points (Smith et al. 1999:168-170). It also possessed items commonly associated with food preparation including a pestle and mortar, bowls, copper cauldrons, pots and pans (Smith et al. 1999:88-105). Emanuel Point II, however, has thus far presented little in the way of military artifacts or utilitarian cooking utensils, aside from four stone cannon balls and a collection of crossbow shafts. A significant number of artifacts recovered from this vessel fall under the category of foodstuffs (Lawrence 2010).
Documentary and archival evidence suggest Emanuel Point II was a nao or navio, a smaller ship commonly used for cargo transport (Phillips 1996:226-227). If in fact, the primary function of this vessel was to carry supplies, in all likelihood it possessed either massive quantities of food or items necessary to construct a colony. Settlers probably transported the majority of the tools, bricks, and other raw materials from the ship soon after making landfall, leaving any stores of food behind for safety. After the hurricane Spaniards recovered the salvageable items left aboard the ships, although most of the food remained waterlogged and inedible (Smith et al. 1999:20). Therefore it is likely that the few utilitarian or militaristic items thus far recovered from Emanuel Point II are, in fact, what Spanish salvagers deemed
26 unrecoverable, left aboard after transporting the majority of the cargo to shore. While these remains from the vessels may reveal certain foodways of those on board before and during the colonization attempt, understanding how these artifacts came to rest at their current locations may reveal what happened in the four hundred and fifty years since.
Site Formation Processes
According to letter written by Tristan de Luna to the Viceroy of New Spain, Spanish sailors immediately began salvaging as much as possible from the wrecks in the days immediately following the hurricane (Priestly 1928). Salvagers gave priority to any items crucial to their survival, as well as recoverable parts of the ships which included rigging, sails, timbers, nails, planks, and whatever else remained undamaged (Rodgers 2003:3-4). Authorities from New
Spain instructed Luna to retrieve any recoverable wood and nails in the hopes that they could use them to construct new vessels (Velasco 1559c:79). These salvage efforts explain both the scarcity of certain artifacts and the scattered arrangement of those left behind.
Post-depositional factors played a role in the layout of both sites as well. Ballast stones left alone during salvage operations insulated the lower hull and protected it from the surrounding environment. Four hundred and fifty years of inclement weather, changing tides, surging waves, and invasive marine organisms demolished what remained of the upper sections of the ship, leaving the lower hull encased by ballast (Smith et al. 1998:19-20). Rudders, gudgeons, sheathing, rigging, damaged ceramics, anchors, and a number of other items surrounded the vessel on the sand bar. Shifting sands and encrustations covered iron and entombed the ballast-covered lower hull and the surrounding materials, enshrouding them with layer upon layer of sediments as each year passed.
27
Layers of sand and faunal remains, identified through analysis of core sediment samples collected from points adjacent to the wreck, provide evidence of four centuries worth of environmental changes in Pensacola Bay (Lawrence 2010:23-24). Such changes demonstrate a gradual yet significant increase in the amount of sand covering the wreck. While some heavier objects did not succumb to the shifting seas, smaller artifacts, like strips of lead for instance, were more at risk of falling victim to the currents and surges of the bay. This could account for the manner in which the sheathing fragments appear strewn about the site; a post-depositional development that occurred potentially decades after the ship’s abandonment.
Lead does not register on a magnetometer; therefore determining where or how much lead was present on these vessels prior to excavation was impossible. Nevertheless, lead was a common material used for sheathing in 1559 and while undoubtedly deteriorated, there was little doubt of lead’s presence (Smith et al. 1998:60). Unfortunately the lead sheathing fragments remained scattered about the sites, both inside and outside of the wrecks, and revealed no analytical information on their original implementation or location on the vessels’ hulls (Smith et al. 1998:60).
2010 Field Research: Motives and Background
Prior to the 2010 summer field school, the question of whether the lead strips originally encompassed the entire hull below the waterline or simply protected the most vulnerable areas, remained unanswered. This line of inquiry developed from the realization that, despite the hundreds of pieces of sheathing collected over the previous four years, the majority of those pieces were fragments at best, most of which measured between five to twenty centimeters in length. Given that Emanuel Point I is thirty-four meters long from bow to stern and Emanuel
Point II measures at twenty-three meters, it is highly unlikely that these fragments provided
28 complete coverage and shielded the entire span of the hull below the waterline. Granted, the possibility exists that the recovered fragments represent just a fraction of the number still buried under sand and silt around both vessels. However based off the evidence at hand, the methods used to keep these vessels adequately protected remains a mystery.
Thus far the only evidence of sheathing still affixed to the ships’ hulls came from the stern section of Emanuel Point I. Archaeologists collected five intact pieces of lead nailed to the sternpost, collected during the 1994 field season (Smith et al. 1998:61). Two samples retained indentations from a gudgeon arm suggesting that these pieces had the specific function of wrapping and protecting the rudder hardware (Smith et al. 1998:61). Small square holes, evidence of the tacks used to hold the lead to the ship, penetrate the sample around the outer circumference of the gudgeon indentation. Uncharacteristically wider than normal, the first sample measures at fifteen centimeters wide while the second measures at seventeen centimeters
(Smith et al. 1998:61). This varies greatly from the majority of sheathing fragments collected from these wrecks, most of which measure on average five to seven centimeters in width. Two of the other lead pieces recovered from the stern, thirteen and seventeen centimeters wide respectively, do not possess gudgeon impressions (Smith et al. 1998:61). However the fact that archaeologists located all four of these larger fragments in one area suggests that common practice was to overlap wider panels of sheathing when protecting critical fixtures on the hull
(Smith et al. 1998:61). While unique in both shape and size, the sheathing recovered from the stern post does not represent the greater collection of correspondingly strip-shaped fragments recovered from both wrecks.
Before 2010 no unit placed on Emanuel Point II showed any indications of attached hull sheathing. Nevertheless, the possibility existed that some amount of lead still remained attached
29 to the ship, as the majority of excavations on Emanuel Point II took place within the hull rather than outside it. The fact that sheathing still remained fastened to Emanuel Point I’s stern suggested the likelihood of a similar presence on the second vessel. Thus in the summer of
2010, I devised a series of excavations aimed at exposing sections of Emanuel Point II’s outer hull in an attempt to identify examples of lead sheathing still affixed to the vessel.
2010 Field Research: Excavations
Archaeologists reburied Emanuel Point I in 1998 to preserve the site for future excavations. Since the discovery of Emanuel Point II in 2006, the University of West Florida maritime archaeology field schools have conducted annual excavations at the site of the second vessel. Emanuel Point II remains listing to port at a twenty to thirty-degree angle relative to the bay floor (Cook et al. 2008:54). As such, the starboard side of the vessel is advantageously angled to allow archaeologists better access to the outer hull. Due to the depth and angle of the port side of the wreck, excavations at certain areas along this side of the outer hull require the use of sand bags and structural supports. Due to limits in time and manpower, I discarded the port side option in favor of focusing on the more easily accessible starboard hull.
Initial plans aimed to continue work in previously excavated one-meter units. Prior investigations of these units had focused on removing sediment from inside the hull, leaving any areas outside the hull and within the unit buried. However only one previously opened unit, designated 83N 500E, remained directly over an area of the starboard hull that included sections of the exterior structure. As one unit was hardly sufficient for this investigation, I planned for the implementation of two new units over separate areas of the wreck.
Two fellow students and I opened unit 97N, 491E on May 20, 2010. The unit was given the designation 97N, 491E based on its location relative to the site’s baseline running along the
30 length of the wreck. We placed the unit above a starboard section of hull that possessed no ceiling planks, only frames and outer hull planking. Removing sediment from between the outer hull and the walls of the unit took just two weeks, though bad weather frequently prevented excavations. We removed sediment with trowel and dredge, steadily revealing more of the outer planks as the work progressed. Aside from two small concretions attached to the outer hull and fragments of lead found detached and adjacent to the ship, no other indication of sheathing was present. After the removal of 71 centimeters of sediment, I declared unit 97N, 491E to be devoid of affixed sheathing.
We reopened the previously excavated unit designated 83N, 500E on June 7, 2010.
Located directly to the portside of the sternpost, this section of planking appeared relatively stable and did not require the use of structural supports. Prior excavation efforts had removed twenty centimeters of sediment from outside the hull but a year’s worth of silty overburden had refilled the unit to the surface; the induction dredge removed this easily. Soon after the excavations in this unit began it was noticed that something solid remained affixed to the hull.
By June 14 we had uncovered a hardened crust on the outside of the vessel covering 61- centimeters of the hull from top to bottom. A large concretion with an outer layer encrusted in shells and rocks appeared to engulf this section of planking. It consisted of one large chunk of stone and sand with no indication of previous form or configuration.
Photographing this concretion proved difficult as it remained entrenched in a deep, narrow hole. Maneuvering the underwater camera into position was simple enough, but adjusting the zoom and flash to compensate for its close proximity to the concretion proved impossible.
Photographs came out either completely white from the flash, or blurry. In addition visibility in this unit was frequently zero, as surrounding excavations clouded the water with sand and silt.
31
On days when we attempted to take photographs prior to starting other work, the standard three- to six-inch visibility in the murky bay made the photos dark and incomprehensible.
Unfortunately, unlike the larger pieces of sheathing collected from Emanuel Point I’s sternpost, this inarticulate concretion presented little in the way of evidence. Whatever sheathing that remained affixed to the hull sat encased within the sand and rock, making any attempts at interpreting its layout futile.
Next we implemented unit 86N, 499E. The unit sat over a promising location for sheathing, directly over a starboard section of hull close to the stern. However on June 24, oil from the 2010 Event Horizon disaster in the Gulf of Mexico entered Pensacola Bay, postponing our work on Emanuel Point II. Excavations in unit 86N, 499E had only reached twenty centimeters in depth before work shut down, exposing only ten centimeters of hull structure that presented no evidence of sheathing. The field school moved inland and focused on wrecks in the
Blackwater River and all projects in the bay remained on hiatus until 2011.
After over a month and a half of excavations, the search for intact, affixed lead sheathing came to a close. The divers discovered only one unit with any evidence of external material on the hull but with no indication of any visible articulation. Granted, the very presence of a concretion suggests that ferrous metals, presumably iron, existed along the hull in unit 83N,
500E. This does not provide a sufficient basis from which to determine the source of this concretion as a medley of iron fittings would attach along the sternpost; the concretion could just as likely be the result of an accumulation of sheathing tacks or components of rudder hardware.
While lead sheathing may still be present at certain sections of the hull, the three units excavated in 2010 revealed no evidence of its presence. Any sheathing originally located at accessible, reachable locations on the hull are presumably scattered around the site. Nothing
32 however is known of the current state of the ship’s keel, or the deeper, more inaccessible section of the remaining outer structure and sheathing may yet remain attached to other sections of the ship.
The lack of empirical evidence from hull investigations fails to present any additional information regarding the degree to which Iberian sailors covered and protected Emanuel Point
II with lead. Thus, this study investigated other avenues of inquiry for pertinent information. The shipwrecks presented little in the way of sheathing articulation, though the fragments themselves contain a wealth of information regarding the specific constituents of lead sheathing. Under closer investigation, these artifacts may yet provide additional data more pertinent to this investigation, specifically concerning their quantity, arrangement, and general effectiveness.
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CHAPTER IV
ARTIFACT ANALYSIS
Lead is undoubtedly one of the more common artifacts recovered from both wrecks, found within almost every unit across both sites. In its purest state, lead is a shiny, gray metal.
After a short submersion in a marine environment, however, a layer of lead sulphide or lead sulfate may form on its surface; trace amounts of lead carbonate, lead oxide, and lead chloride are also common (Hamilton 1998). Lead sulfate is the byproduct of corrosion in an aerobic environment, resulting in a chalky white surface layer created from the oxides in the surrounding water (Hamilton 1998). Alternatively, lead sulphide is the primary byproduct of corrosion in an anaerobic environment and its black color and soft, flakey consistency are the result of sulfate- reducing bacteria (Hamilton 1998). Once present, these outer layers of corrosion form a protective coating, preventing further oxidation.
Archaeologists had recovered one hundred and seventy-one fragments of lead sheathing from Emanuel Point I and over one hundred fragments from Emanuel Point II. Many of the lead fragments recovered from these vessels are indistinguishable as sheathing and are generally too small and mangled to present researchers with any analytical characteristics. Those that retain their original shape and features are rare, though archaeologists have recovered over fifty diagnostically relevant pieces of lead sheathing from each wreck. Despite a few cracks, bends, and warped edges, these pieces still retain most of their original dimensions. These fragments also possess the square holes where tacks penetrated and fastened the lead to the ship.
While many of the lead fragments possess a long and rectangular shape, others are relatively square. The dimensions of the rectangular pieces (or strips) vary but most measure between ten centimeters and twenty centimeters in length. However, one strip in particular from
34
Emanuel Point I measured seventy-five centimeters long (Smith et al. 1999:60). Many of the smaller square pieces measure only six to seven centimeters on either side, though these dimensions vary (Smith et al. 1999:60). The squares commonly have five tacks holes, one on each corner with a fifth passing through the middle (Smith et al. 1999:61).
In Contaduria 877, the financial records of the Luna Expedition, tacks are referred to as estoperoles, the direct translation of which is ‘scupper-nails’ (Mendoza 1596:163; South et al.
1988:41). Shipwrights used thousands of these nails to attach lead to the ship’s hull (Palacio
1986:138). Occasionally archaeologists may find concreted tacks adjacent to sheathing fragments on the Emanuel Point vessels.
An in-depth examination of lead fragments and sheathing tacks may provide information regarding their original articulation and aid in determining whether or not the Emanuel Point vessels possessed complete protection below the waterline. While the overall assemblage of sheathing-related artifacts consists of hundreds of fragments, the majority of smaller, mangled pieces convey very little analytical information. While they were clearly once fragments of sheathing, their current state makes any additional analysis on their arrangement impossible.
Therefore this investigation examines only those pieces of lead still visibly recognizable as sheathing; specifically the strips and squares.
Sheathing Strips
Sixty-two lead fragments from Emanuel Point I and forty-eight fragments from Emanuel
Point II fall under the classification of sheathing strips (according to data compiled after the 2011 field school). Aside from obvious differences in lengths and widths, all pieces share otherwise similar characteristics. They are rectangular in shape (Figure 1); long and narrow with ends that commonly appear ripped and somewhat jagged. Most sides seem straight and even as though
35 precisely cut with a tool. They are fairly intact, although somewhat brittle around the edges.
Most fragments maintain their malleability, though cracks appear if the artifact undergoes any type of pressure.
Figure 1. Strip of lead sheathing
Fortunately for diagnostic purposes lead is a relatively soft metal, impressionable enough for anything nailed against it to leave a mark. Two or three rows of square holes run along the length of the strips, surrounded by a circular impression; the lingering indentation of the tacks’ heads. Few of the tacks used to secure the lead to the ship’s outer hull survived but their impressions are still visible on the strip’s surface.
According to the markings left on the lead strips, the tacks possessed square shanks ranging from four millimeters to seven millimeters on each side. The circular impressions surrounding the holes vary from two to three centimeters in diameter (Figure 2). While undoubtedly the smallest class of fasteners (Smith et al. 1999:80), tacks had the crucial task of
36 holding layers of protective material in place along the ship’s hull. The long shanks passed through layers of lead, resin, tar, and cloth, as well as the surface of the wooden hull itself.
While some strips possess two rows of tack holes, the majority have a third row that runs down the center of each piece. This third row is present in thirty-eight of the intact strips recovered from Emanuel Point I and in thirty strips from Emanuel Point II. Sailors placed these strips directly over the seams between the planks for added defense against teredo worms (Smith et al. 1998: 60-62). Loss of caulking jeopardized hull integrity and inevitably created holes along the vessel from which the ship might flood. Therefore the act of covering the seams with lead prevented, or rather impeded the progress of marine borers within the plank seams (Smith et al.
1998: 60).
Figure 2. Tack head impressions
Assuming that the two rows of nail holes along the sides of the strips secured the lead to the hull, the third row of tacks likely penetrated directly into the seams themselves (Smith et al.
1998:61). As the tacks punctured the caulking material, it ensured that the caulking stayed
37 wedged between the seams (Crisman 1999:260). While acting as a form of protection against teredo worms, the sheathing simultaneously secured and packed the caulking underneath.
While this development does not account for all the lead recovered from these wrecks, it does suggest a logical strategy behind the sheathing’s articulation, one that focused on protecting vital areas of the hull. Understandably, proper sheathing arrangement was a crucial part of administering hull protection prior to a voyage. Failure to properly secure the seams resulted in the loss of ships:
They see that that the sheets of lead are placed, and the last seams are caulked
with the perfection that is so important, and not with the speed with which it is
sometimes done, the result of which is the discovery of some [leaks] of water
when they are very difficult to remedy, and the loss of some ships due to the lack
of this care (Linage 1672:171).
Unfortunately, regardless of how effectively this method sealed in caulking and protected the seams, it inevitably left large portions of the hull exposed to invasive organisms. Teredo worms inevitably bored into unprotected areas of hull with the only indication of their presence the virtually unnoticeable tiny pinholes on the wood2 (Hoppe 2002). Presumably, despite this vulnerability, it was easier to simply provide crews with a patch rather than go through the lengthy and costly measure of sheathing a ship entirely (Smith et al. 1999:62).
After closer inspection it appears as though sailors originally placed the strips of lead directly over the seams leaving the rest of the hull exposed but protecting the crucial areas between the planks. Such partial protection therefore slowed but did not entirely stop the gradual
2 These pinholes went largely unnoticed, not only due to their small scale but also because the thinnest layer of fouling hid them from view (Hoppe 2002). 38 infestation of teredo worms; it also justifies the presence of the second most diagnostically relevant type of sheathing recovered from the Emanuel Point wrecks: the square patch.
Square Patches
Apart from their size the square pieces of lead share similar characteristics to the strips.
Both pieces possess the grayish-white color of corrosion except for those showing the dark, flakey signs of anaerobic bacterial degradation; both possess square tack holes and the round impressions of tack heads on their surface and both are about 2 to 3 millimeters thick. What makes this type of sheathing unique is that the majority of the patches have five tack holes running through them, one on every corner with a fifth at the center (Smith et al. 1999:61).
Occasionally archaeologists recover examples with more tack holes than the standard five
(Figure 3), and occasionally some with less.
The impressions indicate that the tack heads concealed most of the surface area once applied. This would potentially create a tight seal between the lead and the wood, suggesting that shipwrights applied these patches to areas of the hull that required additional protection or repair.
One patch was small enough to cover the tiniest leak in the hull and many used in unison could cover a greater area.
Researchers recovered a number of square pieces of sheathing from the Santa Maria de
Yciar, a vessel associated with the Padre Island wrecks from 1554 (Arnold 1978). Destroyed in
1940 when the U.S. Army Corps of Engineers dredged the Mansfield Cut Channel, the wreck now rests as a disarticulated assemblage of timbers and artifacts strewn across the sea floor
(Arnold 1978). Researchers quickly identified the tack impressions and shank holes on the surface of the lead patches as characteristic of sheathing. While there is no information regarding
39 their original provenience, their shapes and sizes coincide with similar samples taken from other contemporaneous wrecks including the Emanuel Point vessels.
Figure 3. Sheathing patch with eight tack head impressions
In a 1596 manuscript entitled Theorica y Practica de Guerra, or Theories and Practices of War, author and sailor Bernardino de Mendoza (1596:163) lists vital equipment to have aboard for emergency repairs. “…sheets of lead, hammers, nails, [original translation reads estoperoles], cow hides, plugs of wood, blankets, and other necessary things.” It was not uncommon for ships to carry additional lead sheets for repairs from which sailors cut smaller pieces to replace those lost at sea (Lyon 1985:132). In 1587, Spanish sailor Diego Garcia De
Palacio wrote about the common custom of bringing lead sheets aboard an ocean-going vessel:
A ship owner, most prudently, ought to always carry many more spare things than
is necessary, as they are of much benefit and give satisfaction on any
40
occasion…two quarters of pitch, which weigh twelve quintals; four barrels of tar;
250 pounds of oakum; a sheet of drawn lead…(1986:138).
The author goes on to discuss various other supplies, stressing the importance of those crucial to hull protection in case of deterioration or damage. A rector at the Real y Pontifica
Universidad de Mexico and a municipal magistrate, Diego Garcia De Palacio published
Instrucion Nauthica, a compendium of sixteenth-century nautical knowledge, a detailed account of shipbuilding techniques, navigational methods, and essential provisions for every sea-going vessel.
It was important to keep supplies of replacement materials onboard at all times, as sixteenth-century vessels frequently spent months at sea without ever seeing port (Palacio
1986:139; Pérez-Mallaína 1998:10). Vessels used in newly inhabited, colonial harbors rarely had the opportunity to dry-dock for repairs, sometimes mooring for over a year (Pérez-Mallaína
1998:10). A ship’s hull required constant maintenance, as running aground in unexplored seas was as common as leaks, cracks, and the occasional violent encounter with foreign ships or pirates (Pérez-Mallaína 1998:9). Sailors conducted repairs at sea, sometimes in the heat of battle, and a plentiful supply of sheathing and other repair was crucial. Palacio added:
Also, it is usual for some shot to strike at the waterline and penetrate the
bottom of a strong ship…Thus, it is advisable to put the ship on the opposite tack,
and with that, the ship will heel to the other side, and the leak will remain above
water. If the shot-hole is not uncovered by this, artillery, chests, and heavy things
can be dragged to [one] side of the ship, until it is found. The hole being covered,
caulked, and a sheet of lead, lined with canvas… being applied over it, the ship
will be able to navigate and return to fight, if such is agreeable (1986:152). 41
Maneuvering the ship was a key point in this process. One heeled a ship by untying all the guns on the damaged side of the vessel and rolling them to the opposite side of the deck, listing the ship and exposing the damaged section of the hull for repairs (Kemp 1976:632). This was a difficult task, however, as the vessel could potentially be too damaged to heel. In addition, the surrounding environment could prove too hazardous to risk attempting such a maneuver.
Nevertheless it was vital that sailors possess the capabilities of repairing their ships at sea, as they spent a good portion of the year away from port.
The previous quote mentions that the lead was “lined with canvas,” a protective measure when sheathing a vessel. A sheet of canvas between the lead and the wooden planks provided an additional layer of protection from invasive organisms, as well as protection from any possible cuts or abrasions bare lead could potentially inflict on the wooden surface (Stephens 1952).
Sailors nailed tacks through both lead and canvas, forcing fibers from the cloth deep into the wood, further securing the sheathing in place.
Unfortunately for diagnostic purposes, archaeologists rarely find evidence of this material on the Emanuel Point wrecks. The aerobic environment and the corrosive nature of saltwater tend to disintegrate the cloth fairly quickly (Hamilton 1998). Only one sheathing strip, artifact
01038, possessed a remnant of cloth attached to its edge and artifact 00,044, a lead strip with six nail holes, possessed an impression of a cloth weave that resembles burlap on its surface.
Along with these patches, ships would have required a plentiful supply of sheathing tacks. Considering each of the square pieces had five tacks and constant hull repairs and upkeep were required, sailors needed thousands of these tacks on board at all times (Palacio 1986:138).
42
Sheathing Tacks
Of all the fasteners and nails recovered from the Emanuel Point wrecks, sheathing tacks, or estoperoles, are by far the smallest (Smith et al. 1999:80). The tacks are distinguishable by their short shanks and wide heads; wide so as to compress a large area of sheathing into place while piercing through a small amount of space (Castro 2003:14; Crisman 1999:259).
While the circular indentations and square holes visible in the sheathing provided a basic impression of a tacks general dimension, the opportunity to examine a solid, three-dimensional replica allows for a far more thorough analysis. Unfortunately, intact iron tacks from a sixteenth- century shipwreck are a rarity, as the metal generally disintegrates over time. If, however, the iron object begins to concrete, accumulating a layer of calcium carbonate concretion and sand around itself as it slowly corrodes then the chances of examining a three-dimensional version of the original object are significantly higher.
Concretions are a buildup of loose debris and sand that gradually adhere to the exterior of a rusting object attracted to the ions emanating out of the deteriorating metal (Rodgers 2004:78;
Hamilton 1998). The original object continues to corrode until the iron is converted into iron sulfide, leaving a hollow gap at the center of a hard, rock-like casing formed around the exact shape of the original artifact (Rodgers 2004:78-79; Hamilton 1998).
Concretions act like molds, forming a perfectly hollow template of the original object within. It is possible to cast these molds using a hardening resin which fills the gaps and takes the shape of the original object. The process involves accessing the hollow space at the concretion’s center, then cleaning out any remaining iron sulfides within. After pouring a hardening resin into the mold and allowing it to solidify, an air scribe or pressurized pick
43 removes the remaining layer of concretion. What remains is a relatively accurate representation of the original artifact (Figure 4).
Figure 4. Epoxy cast replica of a sheathing tack
The next step is the administration of the hardening compound, commonly Epoxy or
Hysol resin. After removing the concretion using an air scribe, the hardened cast is cleaned and photographed. According to the dimensions of the tack casts from the Emanuel Point wrecks, the shanks have an average length of 3 cm with the longest being 3.2 cm (Smith et al. 1999:84). The shank lengths are typically equivalent to the width of the heads (South et al. 1988:41) measuring from 2.7 cm to 3.2 cm; these measurements correspond to the impressions left on the lead strips
(Smith et al. 1999:84). The tack heads vary in thickness, the smallest being 4 mm and the largest
7 mm. On average the widths of the casted shanks are smaller than those recorded from the holes in the sheathing. While the widths of the holes reach up to 7 mm, the casted shank edges are rarely wider than 4 mm.
It is possible that this discrepancy is the result of poor casting, the result of an insufficient quantity of resin used to fill the molds. However the frequent recurrence of these measurements in every cast indicates a similarity in original design. It is possible the incongruity began once shipwrights nailed the lead to the ship. As the tacks corroded, the heavy lead strips loosened,
44 gradually parting from the outer hull. The significant weight of the lead pressed against the remaining tacks, distorting the lead and changing the shape of the original puncture holes.
Much like how the loss of lead necessitated the transportation of replacement sheathing, so too did the frequent loss of tacks make it necessary for sailors to carry a supply of substitute nails. Diego Garcia De Palacio once again stresses the importance of having spare supplies aboard a vessel:
I shall make known some things, without which one cannot easily depart, and
these are:…four thousand sheathing nails; two thousand scantling nails; two
thousand bottom nails; two thousand medium-bottom nails; one thousand nails for
the ship’s sides; one thousand medium side-nails (1986:138).
The author clearly notes that the four thousand nails brought aboard served as sheathing nails. However, there is no explanation regarding the placement or differences between bottom nails, medium-bottom nails, or side-nails. Regardless, their presence stresses the fact that ships’ hulls required frequent maintenance and repair.
According to the Contaduria 877 records from the Archivo General de Indias, all eleven ships in the Luna fleet brought aboard thousands of nails prior to leaving Vera Cruz (Childers
1999; 359). Records also indicate that salvage played a role in the post-depositional site formation process (Rodgers 2003:3). While colonists did attempt to save crucial parts of the ships, not all tacks would have remained accessible after the storm (Velasco 1559c:79).
The lack of a significant number of tacks in the artifact assemblage of the
Emanuel Point wrecks suggests that corrosion played just as substantial a role in their disappearance as salvage. Hundreds of factors influence the formation of concretions in saltwater environments, including water salinity, pH levels, degree of oxygenation, and most importantly, 45 time (Rodgers 2004:79; Hamilton 1998). Thus it is practically impossible to determine why some tacks became concretions and other simply disintegrated.
Implications and Assessments
The relatively small numbers of intact strips suggest an intentionally scarce application of lead, rather than a lack due to post-depositional processes or flawed excavations. As opposed to sheathing the entire hull, shipwrights would have sought to protect the most vulnerable and vital areas, those that would cause serious detriment to ship integrity if damaged (Smith et al.
1999:62). As archaeologists observed during the Emanuel Point I excavations, the most heavily sheathed section of the hull was the sternpost where sailors essentially wrapped the rudder hardware in lead (Smith et al. 1998: 61). However, these large panels of lead looked nothing like the strips that made up the rest of the sheathing assemblage. Besides the gudgeons, the most vulnerable spot on a ship’s hull was the seams. These required the most protection as they contained caulking that kept the hull watertight. By nailing lead strips directly over the seams, shipwrights would keep the caulking tightly contained between the planks.
Emanuel Point I is thus far the best indicator as to the manner in which sailors chose to cover these vessels in lead. According to the site report, Emanuel Point I likely possessed extensive but not complete sheathing, possessing enough lead to cover only the most vulnerable areas of the hull (Smith et al. 1998:62) This theory seems to align with the lead sheathing assemblage from Emanuel Point II, though it is unknown whether these two different types of vessels obtained similar protection. The strips from both wrecks are relatively wide yet not wide enough to overlap adjacent pieces placed over neighboring seams (Smith et al 1998:62). Partial coverage kept expenses low and did not weigh down the hull, an imperative factor for a colonial vessel carrying substantial amounts of cargo (Smith et al. 1998:62).
46
As mentioned previously, excavations have yet to recover enough lead to indicate complete hull coverage. Only one hundred and seventy pieces of sheathing emerged from a 40% excavation of Emanuel Point I (Smith et al. 1999: iii) and thus far researchers have retrieved just over one hundred pieces from a 25% excavation of Emanuel Point II (Greg Cook, personal communication). The scarcity of lead sheathing is, therefore, likely an indication of partial hull coverage on both vessels.
The Emanuel Point vessels are not unique in this method of hull protection. Many contemporaneous vessels also possessed sheathing of this kind nailed over only the most vital areas of the hull. Archaeologists found the San Esteban, one of the vessels associated with the
1554 Padre Island wrecks, with lead strips attached over the caulked seams of the ship’s hull
(Crisman 1999:260-261). Concreted tack shanks remained wedged between the wooden planks surrounded by tar and oakum, a measure taken to assure the security of the caulking within
(Crisman 1999:260-261).
The Pepper Wreck, a Portuguese Indiaman that ran aground at the mouth of the Targus
River in Portugal in 1606, also had lead strips lining the seams (Castro 2003:14). Like the San
Esteban, the Pepper Wreck possessed lead over its plank seams. However unlike prior examples, this vessel had a unique style of caulking hidden beneath the lead. Dr. Filipe Castro from Texas
A&M University describes it in detail:
A lead strap twisted into a string was inserted into each seam, and two layers of
oakum were pressed against it from the outside. The seams were then covered
with another lead strap, nailed either through the seam, or on both sides of the
seams with iron tacks with circular heads (2003:14-16).
47
While not applied to every vessel, this practice was surprisingly common amongst vessels built in Iberian shipyards (Castro 2003; Crisman 1999; Monteiro and Garcia 1998). The use of lead strings kept the resin or tar soaked fibers from squeezing inwards towards the gap between the outer planking and the ceiling (Castro 2003:14). Simultaneously the nails kept the oakum and string from pushing out as the wooden planks expanded (Castro 2003:14).
Considering archaeologists found the entire system still relatively intact, researchers can assume that it worked fairly well.
While making its way back to Spain in 1622, The Atocha, part of a Spanish treasure fleet, encountered an unexpected hurricane and ran aground (Lyon 1985:2; Mathewson 1986:3).
Archaeologists discovered sheathing fragments on the Atocha adjacent to bundles of six unused
44cm by 46cm sheets of lead (Lyon 1985:132; Mathewson 1986:65). Researchers concluded that sailors used these panels as raw replacement sheathing to repair damaged areas of the hull and applied them when the original sheathing either fell off or required repairs (Lyon 1985:132;
Mathewson 1986:65).
Archaeologists discovered Santa Margarita, also associated with the 1622 treasure fleet, in 1980 off the Florida Keys (Mathewson 1986:3). Excavations recovered large amounts of lead sheathing from around the vessel, all of which looked torn as though ripped from a larger sheet
(Mathewson 1986:67-68). Archaeologists did not find lead sheathing remaining on the hull but rather pieces scattered around the site, much like the Emanuel Point ships. While this wreck sank almost seventy years after the Luna expedition, the scarce number of intact lead fragments suggests a similar system of partial protection applied to the hull (Mathewson 1986:67-68).
48
Summary
Analysis concluded that the scarcity of the lead present on both Emanuel Point vessels suggests a level of priority given to only certain areas of the ship. The third row of tack holes suggests sailors placed the lead strips directly over the seams between the outer hull planks so as to protect and seal in the caulking. Alternatively, larger pieces of lead protected the fittings, specifically those of the rudder hardware.
Despite its popularity amongst contemporaneous vessels, it is impossible to ignore the inherent flaw in this technique: essentially, that a significant portion of the hull remained exposed. Without complete protection, teredo worms invariably fed on the gaps between the sheathing and caused significant degradation to the hull. It seems unlikely that such a problem could have gone unnoticed by those administering the sheathing; thus the possibility exists that sailors only intended to hinder the progress of invasive marine organisms rather than stop them altogether. Sailors expected a certain amount of hull damage over the course of any voyage and spare tacks and sheets of lead allowed for repairs when necessary.
Essentially, the primary goal of the lead strips was to protect and seal the caulking from teredo damage, and while the worms would have had no problem reaching the seams from within the planks themselves, the strips of lead prevented direct access. Whether the worms did indeed penetrate the hull was likely less of a concern than simply maintaining a good seal between the planks. Regardless of its effectiveness, the enduring and widespread usage suggests partial sheathing did provide the seams some degree of protection.
However despite its success at protecting ships’ seams, it remains unknown how long such protection would last. Sheathing’s effectiveness relied solely on its permanence and durability; were the lead to fall free during the course of a voyage, its effectiveness would be a
49 moot point. Many records from this time point to the necessity of transporting replacement lead on board every vessel, presumably due to numerous examples of sheathing loss while away from port.
Records stressing the necessity for replacement sheathing fail to allude to when it became necessary to use them. As mentioned previously, when the British Navy attempted to sheathe their ships in lead, the iron fittings corroded in only a fraction of the time it normally took for such degradation to occur (Petty 1691:45). Unfortunately for this study, these accounts primarily focus on rudder hardware and they offer no mention of the state of the tacks or sheathing.
Whether a ship required replacement sheathing after years, or simply weeks, is unknown.
Transatlantic voyages took months and sailors might have applied replacement sheathing throughout the course of the voyage. On the other hand, the lead may have lasted years without requiring replacement, making the journey to and from the New World many times with its original sheathing along the hull.
Theoretically there exists a direct correlation between the length of time the iron tacks took to rust and the length of time the lead remained attached to a vessel’s hull. While sheathing was undoubtedly at risk from external factors such as running aground or encountering violent weather and rough seas, corroded tacks were likely a far more widespread problem that affected the entire assemblage of lead. Constantly submerged and bearing the weight of the sheathing, tacks underwent considerable and relentless strain for the entirety of their usage. The electrolytic reaction with lead further added to their deterioration, causing the tacks to rust at an accelerated pace. Ultimately, I hypothesize that the expedited rate of corrosion and the overbearing weight of
50 the lead likely caused the tacks to degrade to such a degree that sheathing may have frequently fell free during the course of a transatlantic voyage.
Artifact analysis may provide a number of insights on sheathing practices but it fails to reveal the rate at which these tacks corroded or the permanence of lead once applied to a hull.
Testing the aforementioned hypothesis on tack longevity required a more scientific approach than simple artifact analysis, one that examined the rate of tack corrosion over a predetermined length of time. Using strict scientific methodology, this study tested the theory by constructing a small section of outer planking with sheathing attached, so as to observe the rate of degradation experienced by the tacks over time. The results of this experiment provided a calculated rate of tack longevity and ultimately answered whether sheathing did indeed last the duration of a voyage to the New World.
51
CHAPTER V
EXPERIMENTAL ARCHAEOLOGY
Experimental archaeology is defined as “the fabrication of materials, behaviors, or both in order to observe one or more processes involved in the production, use, discard, deterioration, or recovery of material culture” (Skibo 1992a:18). To conduct such observations, researchers must possess an understanding of contemporaneous factors, scientific methodology, and access to similar, if not identical materials as were originally used (Skibo 1992a:18).
Archaeological experimentation is essentially a deductive means by which to validate or falsify a hypothesis using materials unrelated to written historical sources (Coles 1979:3).
Experimentation allows for the use of inferential reasoning when testing a specific subject through the utilization of methods and materials known to have existed in the past (Outram
2008:2). In various articles, scholars classify experimental archaeology as a means of reconstruction, reproduction, or replication (Mathieu 2002:1; Coles 1979:1; Reynolds 1999:156).
However, opposing scholars tend to denounce these definitions, stating that archaeological experiments do not, in fact, reconstruct items from the past but rather test hypotheses pertaining to the original object while acknowledging the limitations involved in their construction (Outram
2008:2). Many aspects of experimentation are hypothetical, in that they possess unknown variables; that being the case, a ‘reconstruction’ implies that one understands all aspects of the original object, which in turn renders the ‘experimental’ nature of the test worthless (Outram
2008:2-3).
The defining quality of experimental archaeology is its scientific basis, the ability to test measurable hypotheses through the use of controlled variables (Reynolds 1999:156-157). While the archaeological aspect of the test derives from the use of potentially authentic materials, the
52 ultimate goal of the experiment is to produce scientifically testable results without the use of modern laboratory equipment. For example, researchers Gordon Bronitsky and Robert Hamer
(1986) conducted a series of impact and thermal-shock resistance experiments to test the resistance of tempered prehistoric pottery. In lieu of actual prehistoric artifacts, they created bricks of tempered clay with burnt shell, crushed shell, and sand, common tempering substances used by prehistoric Virginia potters (1986:91). Their experiments involved damaging the clay using simple prehistoric methods (dropping, rolling, subjecting them to normal wear and tear) yet their results consist of testable, logical scientific data related to stress fractures and cracks
(1986:91-93). Working to measure the most basic of variables, they extrapolated the results using methodical, mathematical precision. The Bronitsky and Hamer example is a superb representation of experimental archaeology.
In essence, one could almost consider experimental archaeology paradoxical by its very nature, in that scientifically based hypotheses rely on simple, archaic procedures to produce complex, interpretable results (Reynolds 1999:158). Simply by removing the laboratory factor from the equation, the authenticity of the results improves dramatically.
Experimental archaeology separates into two distinct categories: that which examines the creation of an object (imitative) and that which uses the aforementioned creation and examines the various aspects of its function (functional) (Coles 1979:2). Imitative experiments examine the specific methods involved in an object’s construction and attempt to test certain variables pertaining to them, such as durability, strength, or resistance (Coles 1979:2; Outram 2008:3).
Functional experiments build on imitative experiments and use those constructs to test hypotheses regarding their use and purpose (Coles 1979:2; Outram 2008:3). For example, one might design an experiment to test a particular type of weapon. An imitative experiment may
53 observe the various steps involved in constructing such an object, so as to test a hypothesis regarding the processes directly associated with its creation, i.e. the application of heat or the strength of combined metallic alloys. Alternatively, a functional experiment tests for hypothetical factors associated with the weapon’s use, i.e. an arrow’s flight path, a shield’s durability, or a sling’s accuracy (Coles 1979:2; Outram 2008:3; Reynolds 1999:156-157).
My experiment on the longevity of lead sheathing falls under the category of functional experimentation, as its purpose is to observe the rate at which a specific variable, the tacks, deteriorate once exposed to the other materials, the lead, in a saltwater environment. The motive of the test is not to merely construct a section of hull sheathing but rather to observe the subsequent reactions from the sheathing elements themselves.
Certain considerations are necessary to improve the accuracy of any experiment. As mentioned earlier, the use of authentic, contemporaneous materials greatly increases the validity of the results (Coles 1979:2; Outram 2008:4). Unfortunately, such materials may no longer exist and obtaining them may prove problematic as many researchers conduct their experiments far from where the object or process originated (Outram 2008:4). In many cases a compromise is necessary, one that takes every factor associated with the original material into account.
Regardless of the level of accuracy, however, the unknown variables presented by the new material may still affect the testing of the hypothesis (Mathieu 2002:2-3). The methods used to procure natural resources are not as important as the resource itself, though these should conform to the original constituents as much as possible (Mathieu 2002:2-3). For instance, it is unlikely that the presence of machine-cut wooden planks would greatly affect the results of an experiment on ancient ship building practices, assuming one cut the planks to correct specifications. What would affect the results, however, is if the researcher used the wrong species of wood to
54 construct the hull, creating completely unknown variables in terms of strength, integrity, durability, and a myriad of other factors.
With regards to the preparatory process, one should construct an experiment with materials manufactured as authentically as possible. Experimental archaeologists should possess an understanding of preparatory methods pertaining to the time period in question, so as to manufacture as many components of the experiment in an accurate and authentic manner (Coles
1979:3). However, modern means of preparation and procurement are acceptable if (a) there is no alternative and (b) that particular component plays absolutely no role in the hypothesis being tested (Coles 1979:3; Reynolds 1999:156). The most significant risk associated with materials procured through modern methods is the possibility that those methods will in some way alter or influence the subsequent results. For instance, clay composition is drastically different when mixed by machine rather than by hand, despite identical quantities of raw materials in each
(Bronitsky and Hamer 1986:90).
Most importantly, researchers should attempt to remove themselves from the experiment entirely and maintain an objective presence throughout the preparatory, testing, and analytical stages of the test (Coles 1979:3-4). Modern researchers understand life far differently than the past peoples with whom they are concerned and any attempts to imitate or mimic their motives will undoubtedly result in culturally biased results (Coles 1979: 3-4). Only by eliminating a researcher’s own personal influence on the experiment and by approaching the subject with neutrality will the test achieve unprejudiced results.
Sheathing Experiment Goals
Galvanic corrosion occurs when two metals of dissimilar ionic structure come into contact with each other when immersed in an electrolyte, resulting in the deterioration of the less
55 noble metal (the anode) and the deposition of its ions onto the surface of the more noble metal
(the cathode) (Kelly et al. 2003:2). In the case of sheathing, lead is the more noble metal and the iron tacks deteriorate once the reaction begins. The ionic difference between the two metals would be inconsequential if not for the introduction of an electrolyte (in this case salt water) which essentially forms a bridge between the two metals (Kelly et al. 2003:3). Once a connection is established and the iron begins to corrode, the lead attracts iron ions, causing them to drift along the electrolytic path. The iron deposits a visible layer of rust on the surface of the lead
(Kelly et al. 2003:4-5).
Galvanic corrosion is not limited to lead-lined vessels. Iron is just as susceptible to accelerated corrosion when used in conjunction with copper sheathing as when used with lead
(Roberge 1999:32). In 1761 the HMS Alarm received a thin copper sheet that covered its hull completely below the ship’s waterline (Knight 1973:298). The British abandoned lead sheathing as a means of protecting their ships seventy years earlier (Hale 1695), and the HMS Alarm was the first British vessel to receive copper sheathing (Knight 1973:299). At this point in time shipwrights understood the nature of copper’s toxicity and its effect on microscopic marine life
(Trethewey and Chamberlain 1988:3). By applying it to ships’ hulls they hoped to prevent both teredo worms and other marine growths from coming into contact with the wooden planks
(Knight 1973:299).
After a two-year deployment in the West Indies, sailors beached the HMS Alarm and examined her lower hull. According to a 1763 account, they were shocked to discover that sections of the hull appeared completely exposed and unsheathed (Trethewey and Chamberlain
1988:4). What little copper remained hung from the hull by only a few corroded iron nails. The nails looked as though they had “much rotted” since they were first applied (Trethewey and
56
Chamberlain 1988:4). Those that remained appeared to have wax paper wrapped around their heads, the same paper used to wrap the nails during transport to the shipyards prior to their use
(Trethewey and Chamberlain 1988:4-5). Those still wrapped in paper withstood the detrimental effects of galvanic corrosion and remained relatively intact; those without wrapping, however, appeared almost completely corroded (Trethewey, Chamberlain 1988:4-5).
The previous example demonstrates the speed with which galvanic corrosion can occur on a sea-going vessel. It raises the question, however, of why those accounts from the HMS
Phoenix and HMS Plymouth (detailed in Chapter II) mention the corroded nature of the rudder hardware yet failed to mention whether or not the tacks or the lead sheathing were at risk (Mallet
1872:90-92).
In the previous chapter I stated that the galvanic corrosion and the overbearing weight of the lead prohibited the tacks from enduring the duration of a two to three-month transatlantic voyage, thus resulting in the loss of sheathing. Unfortunately, as there are no lead-lined vessels on the high seas today, this theory requires an alternative means by which to test its validity.
In 2010 I constructed a section of a ship’s hull sheathing using lead strips and iron tacks similar to those recovered from the Emanuel Point wreck. By submerging these models in
Pensacola Bay and observing them over a predetermined timespan, I hoped to record the amount of mass lost from each tack and determine the length of time needed for them to dissolve completely.
I decided early on that rather than building one model, two models would allow for the observation of a greater number of variables, specifically the rate of degradation on different sections of a ship’s hull. Therefore I chose to place one model on the bay floor so as to replicate a section of hull that remained permanently underwater. The second model I planned to tie to a
57 dock and keep it partially submerged, so it could experience relatively similar conditions to those at a ship’s waterline. I intended to leave the models submerged for six months as this far exceeded the average duration of a standard two to three-month transatlantic voyage in the sixteenth century (Brinkbaumer et al. 2006; Cohn 1985:685-686).
Construction and Design
In an attempt to maintain a level of authenticity, it was crucial that these models possess similar (if not identical) materials to those of the original ships. Previous examinations of the
Emanuel Point wrecks determined that the ships’ hulls likely consisted of European white oak
(Quercus faginea, also known as Portuguese oak), a species commonly found in southwestern
Europe and used in Iberian ship construction at the time (Oertling 1989:230; Lawrence 2010:97).
Unfortunately it is extremely difficult to obtain European white oak in Pensacola, and after months of searching I compromised and settled on a species of North American white oak known as Quercus alba (Mabberley 1987:130). While not the same subgenus of oak, I believed this substitute to be a permissible compromise in the experiment due to the fact that the timbers themselves play very little part in electrolytic reduction. The need for white oak stemmed from the desire to make the models as authentic as possible; unfortunately, Quercus alba was as authentic a white oak genus as I could obtain.
As ships’ frames never came into contact with the sheathing or the tacks nor did they directly relate to sheathing in any direct way, it seemed permissible to nail two blocks of cheap pinewood across the backs of the white oak planks. While not exactly frames, these blocks kept the planks parallel to one another.
A couple of sheathing fragments from the Emanuel Point wrecks displayed cloth impressions on their surface and one possessed actual cloth attached to its corner. The exact type
58 of cloth is unknown, although the impressions resemble burlap or an equally coarse material with thick weave. Due to these perceived similarities, I chose to substitute burlap in place of this unknown material, purchasing four yards from a local fabric store.
Finding adequately sized sheets of lead in Pensacola proved difficult and despite lengthy searches, both on the internet and at local metalworking shops, lead proved either too expensive or in short supply. Fortunately the conservation laboratory at the University of West Florida possessed recently discarded sheets of lead and these sheets matched the thickness of the lead recovered from the wrecks. With permission, I acquired these sheets for my experiment.
Finding tacks that displayed all the same characteristics as the originals proved more difficult than the search for the lead. Most antique nail suppliers based in the United States use stainless steel so the nails look the same but are strong, long lasting, and corrosion resistant. One supplier did sell wrought iron tacks but treated them with a rust proof polymer prior to selling them. Fortunately, my very generous father was able to locate a small hardware store in Italy that still forges iron tools and construction components by hand. The Italian tacks appeared almost identical in shape to those recovered from the wrecks. From the lengths of the shanks to the widths of the heads, the measurements lined up perfectly.
Construction of the models took just under two days. I first nailed the white oak planks to the pinewood frames and caulked the seams with a mixture of tar and rope, similar to the original oakum placed between the planks. Once the tar dried, I placed a sheet of burlap over the wood. I scrubbed the lead with abrasive clothes and acetone to remove any protective coating and cut it into strips 7 cm wide and 75 cm long.
Later research eventually revealed the likelihood that sailors placed lead exclusively over the seams of the vessels (as mentioned in the previous chapter); however at this point I remained
59 unaware of the degree of coverage on the ships. Therefore, it seemed logical to apply the lead in such a way that each strip touched or overlapped strip adjacent to it, covering most of the models in the process (Figure 5).
Figure 5. Construction of the models with overlapping strips of lead
I then nailed the tacks around the edges of each strip, spacing them at random distances from one another (Figure 6). This arbitrary spacing mimicked the apparently random arrangement of the tack holes on the Emanuel Point sheathing. Those strips of lead placed over the plank seams received a third layer of tacks, applied in a straight line down the center of each piece.
Figure 6. Model with arbitrarily spaced tacks over strips of lead
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I labeled and weighed each tack prior to nailing them to the model in order to obtain their initial starting weights. With these weights, I could make a practical determination of how much mass each tack lost over a six-month period. Model One received fifty-nine tacks and Model
Two received thirty-eight tacks.
I covered Model One with lead from top to bottom, leaving only a few inches of wood exposed on either side of the sheathing (Figure 7). I only applied lead halfway up the face of the second model as I planned to submerge only the lower section from the docks (Figure 8).
I placed Model One on Emanuel Point II’s ballast pile on July 20, 2010. The lead added a significant amount of weight to the wood and it immediately sank once placed in the water. In order to keep the model from moving once in position, myself and other divers filled sandbags with surrounding ballast stones and tied them to the model’s frames.
I placed the second model at Sabine Island on July 26, 2010 where the Pensacola branch of the Environmental Protection Agency is located. With their permission, I suspended Model
Two from one of their docks. Using manila rope to keep the models lashed to the wooden pilings, the lead-clad portion of the replica remained submerged while the top portion hung suspended above the waterline. I used manila rope as it was readily available and unlike metal chains, would not interfere with galvanic corrosion. While the effects of stainless steel (or any other corrosion-resistant metal) on such an experiment are unknown, it seemed prudent to maintain to the guidelines of archaeological experimentation and use only the most basic and natural of resources.
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Figure 7. Model One with complete sheathing
Figure 8. Model Two with partial sheathing
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I visited the models once every month and photographed my observations. Almost immediately the tack heads on both models began turning slightly orange in color (Figure 9). The lead on Model One developed a yellow-green ting, most likely algae deposits from the surrounding brackish water. Model Two also developed a layer of algae as well as a substantial amount of marine life. Thousands of barnacles and snails covered the model after only two months, making it difficult to distinguish where the lead ended and the wood began. Each site visit revealed additional marine growth on each model while the tacks continued to darken in color and change their surface texture, appearing soft and almost spongy as the months passed.
Some unexpected problems did occur. While Model One never needed any adjustments,
Model Two required constant attention. Whether due to the invasive sea life eating at the ropes or the continuous battering from wind and waves, Model Two repeatedly broke free of its riggings and sank to the bottom of the bay. The Sabine Island docks rest at a particularly choppy and rough area of Pensacola Bay, and despite the large quantities of lead nailed to the model’s surface, once the model sank to the bay floor it tended to shift with the flow of water and move locations. Unfortunately I was only able to visit the docks once a month, sometimes making it difficult to determine where the model would be once I arrived, and how long the model had remained submerged prior to my visit.
After three months I abandoned my original plan to duplicate the conditions at a ship’s waterline and instead decided to leave the second model on the bay floor. While Model Two could no longer play a role in assessing the conditions of various sheathing locations on a ship’s hull, it could still provide information on a number of other variables, one of which was bay salinity.
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Figure 9. Model Two after one month of submersion
Deconstruction and Observations
In January 2011 I recovered both models and immediately began removing the tacks and lead from the surface of the wood. Disassembly of the models was crucial as any additional corrosion would alter the final weights of the tacks. As the models were being taken apart, any information associated with their corrosion, degradation, or appearances was recorded. Model
One showed signs of corrosion on and around the tack heads and the lead itself had a thick layer of green algae covering its surface. Aside from a relatively small amount of marine vegetation,
Model One appeared relatively unaffected by marine life (Figure 10). Conversely, barnacles, crabs, and tiny mollusk shells completely covered Model Two, and all that remained recognizable were the brightly colored orange circles running along its lower half. These orange dots stood as evidence of the rusting tacks underneath (Figure 11).
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Figure 10. Model One immediately after removal from Emanuel Point II ballast pile
Figure 11. Model Two immediately after removal from Sabine Island docks
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Though my original intent was to examine tack corrosion, the six-month period underwater provided an opportunity to examine another aspect of ships sheathing, specifically the damage caused by teredo worms. As I began to remove the layers of marine growth from both models, I immediately noticed thousands of pin-sized boreholes and cracks across their surfaces (Figure 12). The unsheathed sections of both models possessed thousands of teredo- larvae boreholes yet when I removed the metal and burlap from the surface of the planks I found only the occasional indication of any invasive organisms (Figure 13).
After chiseling off a section of the planking, however, I discovered hundreds of squirming, translucent teredo worms living just under the surface of the wood (Figure 14). The worms appeared to have completely devoured the planks’ interiors up to a millimeter from the surface. The infestation ran the length and width of both models within the interiors of the planks, and while I had anticipated a small degree of teredo damage, the extent of the final damage after six months was nevertheless surprising.
Interestingly, the salinity of the water appeared to have little effect on the teredo’s progress. The size of the worms seemed comparable (samples from both models measured roughly ten to fifteen centimeters in length), and their girth was identical. While it is unknown whether the extent of this damage occurred during the warmer months of the year or the cold, the fact that so much damage occurred over a six-month period illustrates just how prevalent this threat still is to wooden structures. While no longer a serious threat to modern ships (due to the variety of materials now being used in their construction) harbors that use wooden pilings must still use protective measures against these invasive creatures.
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Figure 12. Teredo damage on exposed sections of Model One
Figure 13. Model Two showing no teredo boreholes under formerly sheathed section
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Figure 14. Internal teredo damage on corner of Model One
Tack Analysis
Immediately following their removal from submersion, the tacks appeared heavily rusted.
Upon closer examination, however, it became clear that the degree of the deterioration was less extensive than originally hypothesized. My original hypothesis assumed that, because of the accelerated corrosive process, not only would the tacks show outward signs of deterioration, but their structural integrity would weaken as well. What appeared to be significant deterioration on the tack’s heads proved to be purely superficial, revealing a shiny, though coarse, façade underneath when rubbed away.
Some tacks appeared to have developed thicker layers of surface corrosion, a hardened layer that easily cracked and fell away to reveal a shiny layer of metallic gray underneath. The most significant signs of deterioration appeared under these loose layers of surface rust, where many of the heads showed more substantial signs of corrosion, with rough edges and pockmarks
68 on their surface. In contrast, the shanks appeared perfectly intact, preserved from corrosive exposure in the wood for the duration of the experiment.
Aside from the slightly corroded heads, the tacks appeared in relatively good condition. It was only after weighing them that the total extent of the corrosion became apparent. Recording the results on a spreadsheet (Appendix A), I weighed each tack using the same digital laboratory scale used prior to the experiment. I then calculated the differences between their starting and final weights, assessing in grams the amount of weight lost over the 6-month test. It was then possible to calculate how much mass each individual tack had lost by converting these values into percentages.
Each of the fifty-nine tacks from Model One weighed an average of 12.35 grams prior to the experiment. After six months of submersion the tacks weighed an average of 10.63 grams, indicating an average loss of 1.72 grams from each. In other words, each tack lost roughly 13.9% of its original mass.
Model Two, submerged near to where Pensacola Bay met the Gulf of Mexico, suffered only slightly greater losses. On average, these tacks weighed 12.41 grams before placed beneath the docks. Once removed, the tacks possessed a mean weight of 10.49 grams, each tack having lost an average of 1.91 grams, or roughly 15.3% of their original mass. While this loss was more than what the tacks on Model One lost, the difference between them was not noticeably substantial.
As is evident in the final data (Appendix A), both models possessed outliers; tacks that deteriorated significantly more or less than others. However, the data suggests that despite a slight difference in water salinity the tacks from both models corroded at roughly the same rate.
After six months underwater, all the tacks lost around 14% to 15% of their original mass.
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The data provided two separate conclusions. First, it suggests that from a strictly scientific point of view, sixteenth-century lead sheathing would indeed have lasted for the duration of a transatlantic voyage. This experiment lasted six months; two to four months longer than the limits of documented transatlantic travel at that time (Brinkbaumer et al. 2006; Cohn
1985:685-686). Excepting any physical hazards met along the way, the data indicates that lead- clad vessels did indeed remain relatively well sheathed for the duration of the journey.
Secondly, these results tell us that not only could the vessel sail from one continent to another without the need for replacement sheathing, but that the ships could potentially make round-trip journeys and still be well-sheathed after returning to Spain. Presuming that the rates of corrosion remain constant, and that after a six-month submersion the tacks lost roughly 15% of their overall mass, then one must simply multiply that six-month period for the length of a voyage to and from the New World. Ships would routinely remain in colonial port for months while crews replenished their food stores and supplies (Pérez-Mallaína 1998:26). Therefore, it is safe to assume that the entire round trip journey across the Atlantic took, very roughly speaking, approximately one year, depending on weather and a myriad of other indeterminate factors.
Twelve months is only twice the duration of the experiment, and evidence suggests the tacks would undergo 30% disintegration at that point.
Given a continued decay rate of 15% every six months, the tacks would eventually corrode completely (or at least to approximately 90-95%), in just over three years. However, it is safe to assume that the lead was at risk long before the tacks completely disintegrated, presuming the exposed tack heads would corrode or fall off long before the shanks did. At the two-year mark, the tacks would have lost 60% of their mass, compromising their structural integrity. At
70 this point the weight of the lead could have potentially hastened any ongoing separation between the head and the shank, causing the tacks to eventually snap in half.
Accounts from the HMS Alarm claim that the copper sheathing was not only at risk after two years’ time, but that a large portion had already been lost (Knight 1973:298). Despite differences in the base metals, these accounts seem to coincide with the results from this experiment. Just as it took two years for the nails on the HMS Alarm to corrode, so would the tacks from Models One and Two take two years to deteriorate to a point where their integrity was at risk. These synonymous results seem to indicate that the rate of galvanic corrosion remains constant regardless of the two dissimilar metals.
Despite lead’s incompatibility with iron and its lack of toxicity to marine life, it sufficiently protected wooden hulls for far longer than was necessary. Upon completion of the return voyage, sailors and caulkers would repair any damaged or exposed areas with new tacks and lead sheathing, eventually allowing the vessel to once again return to sea (Pérez-Mallaína
1998:14).
The fact that vessels could endure a round-trip voyage without needing extensive sheathing replacement implies that any maintenance done at sea or in a colonial port would only require small amounts of lead to do the job. While New Spain did have the ability to produce purified lead at this time (as it was a byproduct of the silver amalgamation process), it is unlikely that an industry based on sheathing would exist in the New World without significant and constant demand. More likely than not, sailors would have brought only what was necessary to repair their own hulls, and only in the direst circumstances would they have relied on an outside source.
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With so little demand for lead in colonial ports, it suggests that most, if not all, lead sheathing was European in origin. Unfortunately, few primary sources exist, or are easily accessible, to confirm or deny such a theory. Such speculation also requires more than interpretive conjecture, based on results from an experiment testing galvanic corrosion. It is impossible to determine a point of origin simply by analyzing the lead’s outward appearance; therefore, investigations must go deeper, and examine the metal from a molecular level.
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CHAPTER VI
A HISTORY OF LEAD MINING AND THE APPLICATION OF LEAD ISOTOPE ANALYSIS
Lead Mining in the Ancient World
There is no evidence in the historical record that indicates when humans first discovered lead. Small cast lead beads dating to 6500 BC stand as the earliest archaeological evidence of its usage, originating from the Çatal Höyük site in Anatolia, Turkey (Cowen 2007:35). One of the first documented references of lead comes from the Bible, in Numbers, when the children of
Israel gave tribute to Moses in the form of various metals. It appears again in Ezekiel XXVII, as a trade good at the fair of the Phoenicians, along with silver, iron, and tin (New Jerusalem Bible).
Beyond biblical scripture, the earliest documented mention of lead exists in 3000-year-old Greek and Hindu texts, specifically pertaining to the techniques associated with shaping the metal
(Eiseman 1978:4).
Lead occurs naturally in two forms: least common as an independent and relatively pure metal (close to 90%), and more commonly combined with other ores, such as silver, copper, zinc, and occasionally gold (Kirsch 1968:74). Pure lead develops deep in the Earth’s crust, subject to intense and constant pressure, while lead-bearing ores commonly occur closer to the surface of the crust. Surface ores frequently develop as lead based compounds, like lead sulfide
(PbS, also known as galena), lead sulfate (PbSO4), or lead carbonate (PbCO3) (Kirsch 1968:90).
While rarely found in its pure form, lead is considered one of the more abundant metals on the planet (Lamborn 1978:17). Only recently has man developed procedures for extracting pure lead from deep below the Earth’s surface, as ancient mining practices could only access shallow surface deposits.
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Ancient exploitation of lead in any widespread capacity came after the discovery of refinement methods, as smelting was necessary to extract lead in its purest form. However, early smelting attempts were likely accidental in nature, the result of a primitive understanding of metallurgy combined with heat (Lamborn 1978:17). Smelting was a simple enough process to grasp, although those performing such a task were likely ignorant of the science behind it.
Placing raw ore amongst fire and charcoal essentially caused the sulfates and carbons present in the ore to evaporate, leaving purified metals behind. As the ore continued to roast, the pure metals within separated as the metal with the lowest melting point began to liquefy. With one of the lowest melting points of any metal (621oF), lead was commonly the first to separate from the ore, leaving the solid, and sometimes precious, metals behind (Lamborn 1978:17-18).
Metalworkers initially considered lead a byproduct of the purification process of precious metals, employing smelting as a means by which to produce gold, silver, or copper (Lamborn
1978:19; Pliny 1967:159). Lead, an impurity of the more coveted metals within, provided little in the way of monetary value compared to its counterparts.
Romans were the first to utilize lead for large-scale urban development (Jones 1980:146;
Pliny 1967:158). While too malleable for certain tasks, such as structural reinforcement or weaponry, lead was nevertheless essential for utilitarian purposes. Resistant to corrosion, lead was an ideal metal for piping, as it could bend and conform to any design while still maintaining a relatively rigid shape (Hodge 1981:486-487). In fact, the Romans were the first civilization to develop sophisticated forms of plumbing, taking advantage of lead’s resilience and malleability to bring water into private residences, while simultaneously transporting waste through the sewer systems beneath the city (Hodge 1981:487). Aqueducts, designed to bring water down to cities from adjacent mountain ranges, frequently had either lead or terracotta clay pipes installed within
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(Hodge 1981:486). Lead’s malleability and conductivity made it an excellent material from which to construct cookware and dishware, and its ability to conduct heat made it an ideal substance for hearths and heating ducts (Hodge 1981:487).
Beyond its conductivity and water resistance, lead was a vital component in a variety of crafts. When mixed with tin or tungsten as an alloy, lead became rigid and functioned as a kind of flux, allowing metal-smiths to solder or weld other metals together. These alloys strengthened cookware, pipefittings, joints, and even rigging on sea-going vessels (Lamborn 1978:18). Potters incorporated lead dust into their clays and glazes, and most makeup and lotions contained lead as a thickening agent (Lessler 1988:79). Ancient glaziers also used lead to tint and color various types of glass (Brill 1969: 255-256). Lead was, essentially, the most versatile and adaptive metal available throughout the Roman Empire, playing an important role in practically every walk of life.
Such versatility, however, came with a price. It is unknown whether citizens of the empire knew of leads toxic nature at the time; however, the problems associated with lead usage quickly became apparent, as explained in the Roman scholar Vitruvius’ book of essays on aqueducts and man-made waterways, entitled De Architectura:
Water conducted through earthen pipes is more wholesome than that through
lead; indeed that conveyed in lead must be injurious, because from it white lead
[cerussa, cerrusite, or lead carbonate, PbCO3] is obtained, and this is said to be
injurious to the human system. This may be verified by observing the workers in
lead, who are of a pallid color; for in casting lead, the fumes from it fixing on the
different members, and daily burning them, destroy the vigour of the blood; water
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should therefore on no account be conducted in leaden pipes if we are desirous
that it should be wholesome (Hodge 1981:486)
An understanding of lead’s poisonous nature rapidly spread as death tolls rose, yet
Roman culture relied far too greatly the metal to end its usage completely. Today, scholars consider widespread lead poisoning one of the more legitimate justifications for the fall of Rome, as it further decayed an empire already on the verge of collapse (Lessler 1988:79).
Every population center in the Roman world incorporated lead into their daily lives to some degree, as evidenced through the widespread poisoning that took place across most of the
Mediterranean basin, suggesting that lead underwent intense cultivation all across Europe
(Lessler 1988:78-79). Archaeological evidence suggests that Roman settlers searched for an ore supply when settling a new location, both for profit and survival, as evidenced by mines in
Britain, Germany, and Spain (Burnham and Burnham 2005; Jones 1980). In fact, in the first century BC, the largest lead producing mines in the Roman Empire were located in Spain along the Rio Tinto River, in an area known as the Guadalquivir Valley (Craddock 1995:12) These mines produced vast quantities of lead along with copper, zinc, sulfur, and silver (Jones 1980:
146-148). Unbeknownst to the Romans at the time, this ore deposit is part of a larger geological accumulation of minerals stretching hundreds of miles across southern Spain, known today as the
Iberian Pyrite Belt (Klein et al. 2009: 59-60). In fact, numerous other civilizations excavated areas of this belt for over 5000 years prior to the arrival of the Romans, including the
Tartessians, Phoenicians, Carthaginians, and Arabs (Klein et al. 2009:60-62).
Directly adjacent to the Iberian Pyrite belt lays another large deposit of minerals in the
Guadalquivir Valley, known as the Ossa Morena Zone, an area rich in copper, lead, silver and zinc (Klein et al. 2009:60-62; Tornos et al. 2004:143). Early Iberian and Argaric civilizations
76 opened these mines around 2000 BC, though the Romans were the first to truly industrialize mining efforts in the region. Through the use of Archimedean screws, water wheels, and air bellows, Roman miners developed relatively sophisticated means to extract water from the pits and supply fresh air (Davies 1935:24-33).
Over time, however, mining efforts waned and eventually disappeared altogether. After the fall of the Roman Empire around the fifth century AD, technological development in rural
Iberia came to a halt. Production of gold, silver, copper, and lead at the Rio Tinto and Ossa
Morena mines peaked around 79 AD, and over the next four hundred years dwindling production rates caused the Romans to eventually abandon the mines altogether (Edmonson 1989:86). Local populations maintained a minimal presence in and around the mines for centuries, extracting small quantities of whatever ore remained in easily accessible surface deposits. However, by 500
AD, all signs of Rome’s industrial mining efforts were essentially gone (Edmondson 1989: 84).
The Rebirth of Spanish Mines
The emergence of Spain as a global power in the fifteenth century led to the establishment of new mines in the Iberian Pyrite belt and the Ossa Morena Zone (Tornos et al.
2004:143; Both et al. 1999). With exploration and colonization came the need for seagoing vessels, and inevitably the need for natural resources from which to build them. Long-term extraction of industrial metals in the Guadalquivir region provided for the construction and repair of ships, which in turn allowed for colonization and transport to and from the New World.
Shipyards needed large quantities of iron, copper, and lead. High demands for each led to the reopening of the most plentiful sources of raw ore in the Iberian Peninsula (O’Flanagan 2008:42-
43).
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Better technology and industrial development in the fifteenth and sixteenth centuries allowed miners to dig deeper than their Roman predecessors, and while mining efforts in Europe focused on utilitarian metals like lead, tin, and mercury, colonists in New Spain concentrated on gold and silver (Young 1970:56-57). Hernán Cortés established the first Spanish settlement in the New World on April 22, 1519, and mining operations began shortly thereafter (Haring
1947:243-244). In 1532 the Spanish Crown issued mining ordinances allowing Spanish settlers to establish silver mines (Haring 1947:244). The first attempt at silver extraction, located in
Michoacán, a settlement west of modern day Mexico City, produced small quantities of silver ore. This scarcity was due to previous mining efforts undertaken by local natives, which had essentially removed the uppermost layer of ore off the surface deposits, thus forcing the Spanish to dig deeper and spend more time and effort than originally planned (Haring 1947:244; Young
1970:59).
The cost of purifying silver ore was also extremely high, a result of inadequate smelting methods. In 1536 a team of four German engineers devised a method of crushing the ore prior to smelting it. Supposedly, smaller pieces allowed more ore to burn at one time (Haring 1947:243-
244). Such a method, while ingenious, was costly and required constant maintenance, as the iron stamps used to crush the ore needed frequent replacement (Haring 1947:243-244). These complications, and the scarcity of adequate ore deposits, made silver an expensive and unfavorable venture.
However, in 1545, through a combination of ingenuity and discovery, silver mining finally turned a major profit. Between 1545 and 1550, Spanish settlers discovered three major sources of silver: at Cerro Rico in Potosí in 1545, at Zacatecas in 1546, and at Guanajuato in
1550 (Bakewell 1971:4-7; Bakewell 1988:16; McAlister 1989:149, 228). In 1554 a Spaniard
78 named Bartolomé de Medina discovered a way to extract silver from raw ore using a process that involved mercury, known today as amalgamation, or the patio process. This technique extracted more silver at a greater degree of purity than ever before (Haring 1947:245-246; McAlister
1989:228).
Amalgamation involved stamping and grinding raw ore into powder using stamp mills powered by water or livestock. Once heated, workers added mercury and salt to the powder. The mercury bound to the hot silver and liquefied it, drawing it from the rock and hardening once extracted. Workers then separated the mercury-silver solution (or amalgam) from the remaining rock debris. After placing the amalgam over a flame, the mercury would boil and eventually evaporate, leaving behind pure silver which workers cast into silver ingots for transportation back to Spain (McAlister 1989:228). The process was highly poisonous to those involved, usually natives or black slaves, due to the mercury fumes they would inevitably inhale throughout the process (McAlister 1989:229). Despite the dangers and loss of life, this method spread rapidly throughout the Spanish colonies.
The amalgamation process explains the presence of mercury on a number of contemporary Spanish shipwrecks, including the Emanuel Point vessels (Smith et al. 1999:119).
It is likely that the colonists planned to search for silver deposits in Florida, making a plentiful supply of mercury on board necessary. Luna’s fleet sank in 1559, so amalgamation was presumably the preferred method for purifying silver at the time.
As stated previously, lead rarely forms as an independent ore, occurring more frequently as a compound mixed with a variety of other metals. Silver naturally bonds with lead as a combination of lead sulfide (galena) and silver sulfide (argentite) (Bateman 1966). During the amalgamation process, the application of heat caused the sulfides to convert to sulfur dioxide gas
79 and evaporate, leaving the metallic compounds behind. Once mercury drew the silver from the ore, what remained was a combination of rock and lead. Once the lead reached its melting point, it seeped from the stone, solidifying once removed from the fire (Lamborn 1978:19-20).
In 1554, mining efforts in New Spain produced three-hundred tons of silver, the largest quantity extracted in any single year since the Spanish first established a presence in the New
World (McAlister 1989:229). The fact that lead was such a common derivative of silver purification suggests that colonists also produced equally vast amounts of lead (relative to the extraction of silver). However, had the citizens of New Spain possessed the capability to create a lead-based industry, their efforts would have undoubtedly met resistance from the Spanish crown. In order to protect their interests, Spanish authorities discouraged all major industries in
New Spain not associated with agriculture or mining, the two most profitable enterprises in the colonies at the time (Haring 1947:242). While not specifically a ban, these warnings ensured that colonists relied on the motherland for supplies and goods, while discouraging anyone from branching out beyond their agricultural or mining responsibilities. A restriction on any oppositional industrial development prevented colonial independence and continued to turn a profit for Spain, both through the cultivation of natural resources and the importation of necessary goods (Haring 1947:242).
However, the Spanish crown permitted a small degree of mercantilism. Officials encouraged colonists to produce their own food, clothing, and cookware when needed, so as to maintain a relative degree of comfort. Even small-scale production required raw materials like hemp, silk, fruit (for wine), and ore, all of which colonists grew or could extract from the natural world around them (Haring 1947:2:43; McAlister 1989:226). Thus, the possibility exists that colonists manufactured small amounts of necessary items from lead, so as to maintain a certain
80 standard of living. For example, blacksmiths used lead alloys to join various metals, and colonial ceramics contained lead-based glazes (Inanez et al. 2010:2698). Fortified Spanish wines and certain types of rum contained sapa, a sweet lead acetate syrup made by boiling grape rinds in lead containers (Lamborn 1978:22). Lead acetate also possessed a salty aftertaste, making it an everyday spice added to most food.
While certain manufacturers did employ lead to some degree, it was never in any vast quantity. It certainly fell short of industrial levels, and it is unlikely colonists used it for producing anything other than small, utilitarian items. It seems improbable that ship builders used lead extracted from colonial mines to sheathe large fleets of ships, specifically those involved in the 1559 expedition to Pensacola.
A number of factors point to this conclusion. The previous chapter demonstrated how lead sheathing could indeed last the duration of a round trip voyage from Spain to the New
World. These results indicated that it would take roughly two years for the iron tacks holding the lead in place to weaken and lose structural integrity. Therefore, a colonial supply of lead was relatively unnecessary, as any ship actually requiring outer hull repairs could simply transport their own supply of lead.
In addition, as mentioned earlier, Spain was producing large quantities of industrial metals like copper, iron, lead, and zinc, while colonial mines focused on profit, specifically from gold and silver. While the silver mines produced a large amount of lead for the colonies, Spain’s involvement in exploration and colonialism undoubtedly required more utilitarian metals than
New Spain could yield.
To summarize, factors on both the colonial side and the Spanish side make it highly unlikely that the lead recovered from the Emanuel Point shipwrecks originated in New Spain.
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Colonial mines were too new and too focused on the extraction of precious metals to refine enough lead for every ship arriving in their ports. In addition, a discouragement of large-scale industry made producing anything that might potentially threaten Spanish profits difficult, such as sheathing for all of Spain’s sea-going vessels.
However, these theories remain purely conjecture without hard evidence. Without a manufacturer’s stamp or a maker’s mark visible on the remaining sheathing, an alternative means of pinpointing the source of the lead is necessary. Instead of focusing on the lead’s outward appearance, however, such examination requires the use of chemical testing, specifically, a process known as lead-isotope analysis. For years, archaeologists and historians have utilized lead isotope analysis to help determine the provenience of various materials. Using thirty samples taken from the Emanuel Point ships, the following analysis aims to confirm whether the sheathing was indeed Spanish in origin, or whether small-scale colonial mercantilism possessed the capability of refining lead on an industrial scale.
Lead Isotope Analysis: Background
In order to understand the specifics behind lead isotope analysis, a brief discussion on isotopes is necessary. Isotopes are atoms that contain a different quantity of neutrons than the normal number in a given element. Different atoms of the same element can possess varying numbers of neutrons though the number of protons stays the same. Referencing a specific isotope involves stating the number of neutrons that atom contains. For instance, a carbon isotope with six neutrons would be 14C. The variances between the numbers of neutrons present in each element are generally dependent on the manner in which the element originated, as well as their current state of decay (Laeter et al. 2003:697-700).
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Billions of years prior to the formation of our solar system various elements were already present, drifting outward from the Big Bang. Over time those elements coalesced and violently fused into massive cosmological bodies. A small percentage of the original isotopes present at the start of the universe fused into those bodies and still exist today, categorized as primeval or primordial isotopes, never changing or decaying (Russell and Farquhar 1960:25-43). However, the majority of the elements present on Earth are the current form of ever changing isotopes, ones that started out as one element but decayed into another. During the course of decay, many elements become radioactive and lose nuclear particles, eventually transforming into completely different elements altogether (Russell and Farquhar 1960:25-43).
The element lead contains four stable isotopes of varying atomic mass: 204 Pb,
206 Pb, 207 Pb, and 208 Pb. Only 1.4% of all lead on the planet contains the 204Pb isotope, making it both the rarest and most essential isotope in the analytical process. 206Pb and 207Pb are examples of transformed isotopes, as they are the current state of decay of two different uranium atoms: 238U and 235U, respectively. 235U has a half-life of 704 million years, and 238U has a half- life of 4.47 billion years, older than the suspected age of the Earth. Alternatively, 208Pb is the current form of thorium (232Th), which possesses a half-life of 14.5 billion years. Interestingly, some scientists claim this is older than the age of the universe itself (Russell and Farquhar
1960:2-9; Gale and Stos-Gale 2000:505-508).
The process by which uranium and thorium decay to produce a stable lead end product is long and complicated, and the original elements must undergo numerous intermediate steps prior to complete conversion. Each phase of the conversion can last anywhere from milliseconds to millennia, but the results are always the same. While these elements inevitably convert to lead regardless of their location on the Earth’s crust, surrounding geological factors do, however, play
83 an influential role throughout the decay process (Gale and Stos-Gale 2000:508-512). These influences are the basis for lead-isotope analysis.
Like all elements on Earth, lead is a product of its environment, possessing a unique geologic signature based on billions of years of change. Lead develops a distinct regional history as it forms, entirely unique to its location of origin, the result of thousands of different materials physically and chemically mixing over time (Laeter et al. 2003:702). The specific processes involved in forming metallic deposits are especially complex and involve high temperatures and intense pressures. As regions of the Earth’s crust develop their own geologic identity, so too do the metals within. In this way, the four stable isotopes present in lead occur in unique and specific concentrations, based on the geological composition of their surrounding environment.
By comparing the concentrations of the four isotopes in a given sample of lead against the isotopic qualities of a known source of ore, it is possible to determine, with relative certainty, the sample’s point of origin (Gale and Stos Gale 2000). However, this type of analysis is not absolute. While no two areas on the planet are the same, certain regions do share similar characteristics, both above ground and below. Similarities in the surrounding geology can create ores with extremely similar isotopic properties, and while not identical, these similarities can lead to somewhat inaccurate determinations regarding sample provenience (Dr. George
Kamenov, personal communication 2011).
Applying known archaeological interpretation to the results of lead isotope analysis allows researchers to justify their conclusions, as well at determine whether their results make logical sense. For example, a widespread civilization like the Romans, who utilized lead in their everyday lives, would logically obtain the ore from a large, plentiful source close to the their own sphere of influence. Should isotopic analysis reveal that an artifact made from Roman lead
84 matches the isotopic characteristics of a mine from halfway across the globe, it would be safe to assume that these similarities are the result of relatively similar geologic deposits, rather than proof of an unknown chapter in Roman history. While this is a considerably exaggerated example, it demonstrates how one’s knowledge of cultural context can aide in the interpretation of isotopic analysis.
Technological Development
The actual methods involved in lead isotope analysis have become progressively more sophisticated over the years, reducing cost and increasing accuracy as technology continues to evolve. First emerging in the 1960’s, isotopic analysis, or archaeometry, originally relied on such techniques as thermal-emission mass spectrometry (Brill and Wampler 1967), conventional magnetic sector mass spectrometry (Farquhar and Fletcher 1980, 1984), and atomic absorption spectrophotometry (Walthall et al. 1980; Walthall 1981). While considered revolutionary in the archaeological field at the time, these methods were slow, costly, inaccurate, and the machinery was expensive and difficult to use. Sample contamination was also a constant problem, as tests involved dozens of steps that required repeated sterilization.
In the late 1980’s thermal ionization mass spectrometry (TIMS) provided the most cost effective and accurate means by which to determine isotopic values. However, this method was still far more expensive than what many researchers could afford, and the procedures still required extensive sterilization and preparation (Pomies et al. 1998:147-149). It was necessary to extract all lead from a sample prior to testing with TIMS, as the procedure required precise calibration and only measured lead isotopes; any outside ‘contaminants’ rendered the results inaccurate (Gale and Stos-Gale 2000:518-519).
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Today, archaeologists primarily rely on inductively coupled plasma mass spectrometry
(ICP-MS), as it can quickly and cheaply run dozens of samples in a short period of time.
However, early attempts at using ICP-MS resulted in less accurate results than those produced by
TIMS, due to the fact that ICP-MS employed a single ion beam collector in conjunction with a quadrupole mass spectrometer. In other words, the component that broke the lead down to its basic atomic structure (the quadrupole mass spectrometer) fed too much information at one time into the component that analyzed the data (the ion beam collector) (Baker et al. 2006). The flood of data would overwhelm the device, forcing it to pick and analyze atoms at random, finally presenting the results as a concise, yet completely indiscriminate, set of calculations (Gale and
Stos-Gale 2000:520-522). Fortunately, the development of a multiple ion beam collector improved on ICP-MS technology, and when used in conjunction they produce the most accurate results of any isotopic testing procedure to date. Known as multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS), the technique is now considered the standard method for conducting isotopic analysis (Baker et al. 2006).
MC-ICPMS requires that the samples dissolve in acid prior to analysis, as dissolution removes outside contaminants capable of distorting results. The only other comparable technique to acid dissolution in mass spectrometry is the laser ablation method, which requires no sample extraction but instead utilizes a high-powered laser to vaporize a small crater on the surface of the sample (Young and Pollard 2000:23). The resulting vapors are then broken down and analyzed in the mass spectrometer, in a similar manner to that of the dissolved solution.
However, these tests tend to be far less accurate than the acid dissolution method, as laser ablation functions in a vacuum, requiring complete sterilization of the environment prior to testing. Any free-floating particles could potentially blend with the vapors and alter the resulting
86 analysis. In addition, laser ablation normally tests samples with very little lead, as in the case of clays or lead-based glazes. Any test involving pure metallic samples of lead, lead shot or sheathing for instance, could potentially damage the finely calibrated equipment (Young and
Pollard 2000:24-25). Acid dissolution remains the most accurate means by which to conduct mass spectrometry analysis, and is the most commonly used method for testing samples of pure lead today.
After determining a sample’s theoretical provenience using historical analysis, it is then possible to search for relevant isotopic data emanating from that part of the world. Fortunately, archaeologists, geologists, and scientists have conducted MC-ICPMS analysis on thousands of samples from all over the Earth for years, presenting their results in various publications and conferences. The amount of data regarding isotope studies presently in the public domain is vast, and finding comparable sources from most locations on the planet requires little more than simply conducting a search through periodicals on the internet.
Invariably, researchers around the world conduct their analysis in different laboratories.
While varying equipment could create problems for data comparison, it is in fact possible to compare two or more sets of data generated by different laboratories due to the use of an international calibration standard. Across the globe, laboratories employing MC-ICPMS constantly calibrate their machines using two standard lead sources of known isotopic value, known as Standard Reference Material 981 (SRM 981), and SRM 982 (Gale and Stos-Gale
2000:518).
Established by the United States National Institute of Standards and Technology (NIST),
SRM 981 and SRM 982 contain 99.9% purity and are sold to MS-ICPMS laboratories in the form of finely coiled wire. SRM 981 comes from a batch of natural homogenous lead, derived
87 from a practically pure source and mined from a single location on Earth. SRM 982 contains a mix of radiogenic lead altered to contain equal abundances of 206Pb and 208Pb, essentially an equal share of what was once uranium and thorium (Baker et al. 2006:50; Barnes et al. 1986:14-
15). The NIST provides the percentages of each stable isotope present in SRM 981 and SRM
982, including the + tolerance of each (Dr. George Kamenov, personal communication 2011):
SRM 981 SRM 982
204Pb 1.4255 + 0.0012 204Pb 1.0912 + 0.0012
206Pb 24.1442 + 0.0057 206Pb 40.0890 + 0.0072
207Pb 22.0833 + 0.0027 207Pb 18.7244 + 0.0023
208Pb 52.3470 + 0.0086 208Pb 40.0954 + 0.0077
The establishment of a universal standard of calibration allows researchers to compare two or more samples against one another, secure in the knowledge that any data obtained from foreign sources is equally as reliable as their own.
Sample Preparation
I chose thirty sheathing samples from the lead artifact assemblages of both Emanuel
Point I and II, fifteen from each wreck. I chose these samples based on their distinct points of recovery, ensuring I obtained a wide selection from various locations around each vessel. I also chose samples representing both the larger, rectangular pieces, as well as the smaller, square pieces, so as to represent what appear to be both patches and strips.
Prior to dissolving the samples in acid, I scanned the thirty pieces of lead sheathing with a hand held x-ray fluorescence device (XRF), generously lent to the University of West Florida archaeology department by INNOVX Systems. XRF is a relatively new tool in archaeology, designed to essentially analyze the elemental makeup of a metallic object. MC-ICPMS requires 88 the use of such devices to determine the percentage of various elements in the sample prior to acid dissolution, as certain substances can influence test results (Dr. George Kamenov, personal communication 2011). Until recently, miners and geologists exclusively used XRF technology to determine the percentage of metallic ores in a given area. Now however, archaeologists utilize the technology to establish the purity of various metallic artifacts, and to see what other elements might be present.
A portable hand-held XRF is relatively easy to use, requiring only the most basic understanding of chemistry to interpret the final readings. Held like a gun, the device points towards the artifact. After pulling the trigger, a beam of radiation hits the artifact and rebounds back to itself. Each sample requires at least forty to fifty seconds of testing, during which the invisible beam of radiation proceeds to agitate the atoms present in the sample. Every element contains atoms uniquely structured to an element’s basic design, and the electrons present in those atoms maintain just as rigorous a framework. When analyzed with an XRF gun, the radiation beam essentially knocks an electron out of each atom, and replaces it with one of its own, matching the exact speed, course and function originally performed by the missing electron. Once the beam returns to the device, a computer analyzes the behavior of the electron left behind; identifying a distinct pattern from which it can identify exactly which element the electron now mimics (Brackett 2011). The computer can also determine the number of invasive electrons present in the sample after infiltration, and how many of each behaves similarly. In other words, it can calculate how many of each ‘replacement electron’ mimics those belonging to lead, or iron, or copper, thus drawing conclusions as to the percentages of each metal in a single sample. Finally, the results display on a PDA screen, shown as percentages of each metallic element present in the artifact.
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XRF is not a substitute for isotopic analysis in the field of archaeometry and provenience studies. While isotopic analysis examines a sample’s atomic structure, XRF looks at the quantities of each element in a single sample (Brackett 2011). Metals change their elemental makeup overtime due to the surrounding environment. Even if the most abundant metal in the object, copper for example, remained fairly intact, it is entirely possible that the artifact absorbed small quantities of various other metals over time as a result of centuries of burial (Brackett
2011). Regardless of whether two metal artifacts originated at the same mine, their current composition would reveal more about their surrounding environment, rather than their original.
XRF is an inadequate substitute for isotopic analysis specifically because metal compositions change over time (Brackett 2011). Using a toothbrush and baking soda I removed the outer layer of oxidation from each section of lead, making sure to only expose what was necessary (usually about a square centimeter). I then scanned the samples, logging the results on a spreadsheet
(Appendix B).
According to the resulting data, only two of the sheathing samples (EPI-01561 and EPII-
2382) contained 100% lead. Aside from those two artifacts, the rest contained a mix of lead (Pb), iron (Fe), tungsten (W), zinc (Zn), zirconium (Zr), and tin (Sn). As was expected, all samples containing traces of other metals had a higher percentage of lead than anything else, ranging from 85.5% to 99.9%. The only other metal with any significant presence was iron, which ranged from 0.11% to 14.3%. All other impurities present within the samples are hardly worth noting, as they exist at less than 1%, and not enough to hinder test result. Only one artifact, EPI-
00600, contains over 1% of tungsten, a common metal found in conjunction with lead ore.
Typically, iron is not a common metal found in conjunction with lead ore, nor was it used in the amalgamation process (Bateman 1966:42). It is possible that the iron is a depository
90 residue from the iron tacks used to hold the lead in place, a result of the galvanic corrosion process mentioned in chapter five of this study. While tack heads deteriorated and deposited small amounts of iron on the lead, larger iron fittings would decay faster and leave larger deposits, a probable explanation for the wide range of iron within each piece.
A major consideration, prior to testing with MC-ICPMS, was whether the lead samples contained mercury (Hg), a major component in the amalgamation process. Mercury can not only damage the MC-ICPMS instrumentation, but also greatly influence the results of the test (Brill and Wampler 1967; Kamenov et al. 2004). It would have been necessary to use a different piece of sheathing had any artifact tested positive for mercury. As the XRF data presented no evidence of any mercury, sample preparation for MC-ICPMS analysis could begin.
I prepared the samples for analysis as per the instructions of Dr. George Kamenov,
Assistant Professor of Geology at the University of Florida. The first step involved washing thirty high-density polyethylene (HDPE) bottles with deionized water. I then filled them with
10% nitric acid solution using more deionized water and trace metal nitric acid (HNO3). After allowing the solution to sit for two days, I discarded the acid and again rinsed the containers in deionized water, verifying that the containers were free of any trace substances.
Using a Mettler Toledo XP milligram scale, I measured 1 milligram (1mg) of lead from each of the thirty samples using a razor and a pair of tweezers. Slicing through the oxidized layer on the surface of the lead, I took a small sliver from inside the core of each piece of sheathing, where the metal still maintains its grey and polished appearance. After measuring each sample, I carefully transferred them into the HDPE bottles, making sure to marks the lids with the correct sample number.
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I poured five milliliters (5ml) of trace metal nitric acid (HNO3) into the HDPE bottles and waited for the lead to dissolve. After five minutes, the flakes turned a pale white color, and after ten minutes they dissolved completely. I then added ninety-five milliliters of deionized water to each container. The resulting mix was a 5% HNO3 solution containing ten parts per million of lead (10 ppm Pb).
I prepared the samples in the conservation lab at the University of West Florida three weeks prior to testing. In February of 2010 I transported the samples to the University of Florida in Gainesville to run the thirty samples on the MC-ICPMS in the Department of Geological
Sciences. The samples required further dilution, as 10ppm was too strong a solution for the mass spectrometer to detect with any accuracy. Additional dilution simply required transferring 10 ml of the prepared sample solution using a sterilized pipet into another HDPE bottle containing 90 ml of deionized water. The final solution contained 1 ppm of lead, an adequate concentration for the MC-ICPMS instrumentation.
For each test I transferred 25 ml of a single container’s solution to a sterilized Teflon vial, used specifically for introducing samples into the MC-ICPMS. Samples were administered directly to the plasma chamber through a Nu Instruments Aridus desolvating nebulizer, with an uptake rate of 100 µ1 min-1 (essentially a measure of the quantity of each sample run during a single analysis, and the time taken for the sample to pass through to the plasma chamber).
Analysis of each sample took just under ten minutes, after which the mass spectrometer (Figure
15) provided a digital readout for each.
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Figure 15. The Multiple Collector-Inductively Coupled Plasma Mass Spectrometer at the University of Florida Data Analysis and Comparison
As a sample breaks down into its integral fragments, the mass spectrometer separates the lead on an atomic level and records the abundance of each of the four separate isotopes within each atom (Kamenov et al. 2004: 1262-1263). Preset equations built into the analytical receptors of the machine then compute a series of ratios between the given isotopes. The resulting data appears as sixteen separate sets of ratios. While each ratio can be useful in determining provenience (Gale and Stos-Gale 2000:507), recent technological advances in MC-ICPMS instrumentation have established a set of three ratios that researchers generally consider to be the standard by which to compare samples (Baxter et al. 2000:117):
206Pb/204Pb 207Pb/204Pb 208Pb/204Pb
Radiogenic lead, or 206Pb, 207Pb, and 208Pb, exist in much larger quantities on the planet than primeval lead, 204Pb. Determining the proportionate amount of primeval lead in comparison to its more plentiful counterparts is therefore the most accurate means by which one can
93 determine provenience, as its rarity allows for pinpoint accuracy (Gale and Stos-Gale 2000).
Due to limited instrumentation and technology, early attempts at isotope analysis failed to accurately measure primeval lead. These limitations constrained early researchers to work with only alternative ratios, determining isotopic values based on the more easily identified radiogenic lead isotopes. Thus researchers adopted 206Pb, considered the rarest of the radiogenic lead, as the common denominator for ratio calculation (Baxter et al. 2000:115-120). Without the ability to accurately incorporate 204Pb into their measurements, early provenience studies used the ratios
208Pb/206Pb and 207Pb/206Pb. Despite advances in technology, modern provenience studies still incorporate these ratios into their analysis, as many older, and potentially comparative, studies consist of readings based solely on radiogenic lead.
A series of bivariate plots integrate data from all four isotopes for visual pattern recognition. It is common practice to create two bivariate graphs, each comparing two distinct ratios (Gale and Stos Gale 2000:522-523). This study includes two graphs for each set of data: one comparing ratios based on radiogenic and primeval lead (208Pb/204Pb and 207Pb/204Pb), and one comparing ratios based solely on radiogenic lead (208Pb/206Pb and 207Pb/206Pb). While any two ratios may be compared, using both purely radiogenic ratios and combined allows for the analysis of five, rather than simply three isotopic values. This, in turn, allows for more precise determinations regarding provenience. The missing 206Pb/204Pb ratio proves unnecessary in these graphs as all other ratios contain the 206Pb and 204Pb isotopes, eliminating the need for additional representation.
The generated data appears in a scatter plot, commonly clustered together depending on the degree of variation between samples. Corresponding provenience with a comparative sample ore relies entirely on the degree to which both data clusters converge around the same point.
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However, the possibility of establishing a positive correlation with a comparative sample ore depends entirely on whether both sets of data cluster reasonably well together within both bivariate graphs (Gale and Stos Gale 2000:522-523; Baxter et al. 2000:117).
Initial results of isotope analysis appear in the form of a spreadsheet (Appendix C) from which one can subsequently interpret the data in graphical representation. On its own, a spreadsheet allows for the determination of numerical ranges between isotope ratios. The ranges between the highest and lowest ratios for each sample of lead sheathing are small, and are as follows:
208Pb/204Pb = 38.40649 to 38.43475 = .02826
207Pb/204Pb = 15.6223 to 15.63363 = .01133
206Pb/204Pb = 18.46641 to 18.48502 = .01861
208Pb/206Pb = 2.079252 to 2.080008 = .000756
207Pb/206Pb = 0.8458427 to 0.8460939 = .0002512
As mentioned previously, isotopic ratios vary depending on their location on Earth, due to various geophysical and environmental variables (Schooler 2009:23). The ranges above are relatively small and possess little statistical dispersion in terms of varying geological provenience, as it is common to see major differences in isotopic properties in the first or second numeric value of the given ratio (Schooler 2009:23). The lack of significant range between each sample’s ratios indicates that they all share relatively similar proveniences. Therefore, while at this point it is impossible to determine a point of origin without a comparative database, on their own, this data suggests that all thirty samples originated from relatively the same geographic location on Earth. Independently, this is an illuminating discovery, as it eliminates the possibility that the sheathing contained a mix of lead from both Spanish and Mexican (New Spain) sources.
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It also suggests a major source of lead, as these samples came from two separate vessels, and it is unknown whether construction of these ships occurred at the same time.
Arranging this data on bivariate plots illustrates the degree of dispersion between samples. The first graph (Figure 16) compares the isotope ratios 208Pb/204Pb (y-axis) against
207Pb/204Pb (x-axis). The second graph (Figure 17) compares the isotope ratios 208Pb/206Pb (y- axis) against207Pb/206Pb (x-axis). Each graph contains a single cluster consisting of thirty separate sample markers, and as is evident, each maintains a relatively close proximity to the others. However, a single outlier appears in each graph rising exponentially from the other markers on the both axes. While the small difference in isotope ratios could potentially hint at an alternative point of origin, these outliers possess relatively insignificant degrees of deviation from the other samples. Should such differences actually indicate a varied geological provenience to the other samples, the variation would be slight, not enough to suggest a completely alternative extraction site. What might seem like a substantial difference between samples becomes inconsequential once plotted alongside comparative ores, as all points may eventually demonstrate an inclination towards a single site.
I examined a number of comparative databases for this study, containing information related to isotope studies from various locations across Europe, so as to provide a set of data from which I could identify corresponding ore sites (Baker et al. 2006; Bode et al. 2008; Brill and Wampler 1967; Gale and Stos-Gale 2009; Hunt 2003; Klein et al. 2009; Pomies et al. 1998;
Villa 2009; Zalduegui et al. 2004). The most comprehensive assortment of isotope ratios from
Southern Iberian ores, and the database used in this study (Appendix D) came from Dr. Ignacio
Montero Ruiz (electronic communication 2011), professor of archaeology and an authority on the subject of archaeometallurgy at the University of Seville.
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Lead Sheathing Samples 38.48
38.46
38.44
38.42
38.4 Lead Sheathing 38.38 Samples
208Pb/204Pb 38.36
38.34
38.32
38.3 15.6 15.61 15.62 15.63 15.64 15.65 207Pb/204Pb
Figure 16. Scatter plot of lead isotope data for sheathing samples using radiogenic and primeval ratios
Lead Sheathing Samples 2.082
2.081
2.08
2.079 Lead Sheathing Samples
208Pb/206Pb 2.078
2.077
2.076 0.845 0.846 0.847 207Pb/206Pb
Figure 17. Scatter plot of lead isotope data for sheathing samples using radiogenic ratios
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Included in the database are the standard five isotope ratios, as well as each sample’s region, mine, and published source of origin. Such information is extremely useful to comparative analyses, as it provides crucial information for each set of data, eliminating the need for additional research into the specifics of each site.
Despite the need for a basic understanding of chemistry throughout the process of sample preparation and analysis, the actual process of data comparison is relatively straightforward. It is first necessary to identify the principal region or zone from where the samples originated, effectively narrowing the focus of the search down to only a few mining sites within a specific area (Zalduegui et al. 2004:625-626). In the case of the sheathing, this search is done by comparing the average of each given isotope ratio, essentially an overarching value representing all sheathing samples within that given ratio, against the sample ores collected from an entire region. After identifying a region possessing statistically similar sites, more direct interpretation occurs using graphical representations of these select regions plotted alongside the thirty sheathing sample ratios. Hypothetically, correlations then become visible between the sheathing samples and a specific mining site within these given regions, essentially establishing a reasonably identical provenience (Schooler 2009:23-27)
Again, the initial step in this analysis requires determining the average value of each given isotope ratio, so as to create a set of standard values that may potentially identify a specific region within the comparative databases. By matching these numeric values to those listed in the comparative databases, a trend appears that suggests an analogous provenience with Iberian ores.
The strongest similarities come from two distinct regions, known as the Ossa Morena Zone and
Los Pedroches (Appendix D). The average value of each of the isotope ratios for the sheathing samples are as follows:
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208Pb/204Pb = 38.41849567
207Pb/204Pb = 15.6267853
206Pb/204Pb = 18.471562
208Pb/206Pb = 2.079873967
207Pb/206Pb = 0.845989747
According to the comparative database, the Ossa Morena Zone is one of the larger deposits of metallic ores in southern Iberia, comprised of at least one hundred and two known historic mining sites. The Los Pedroches region is smaller than the Ossa Morena Zone, located inside a much larger ore deposit known as the Central Iberian Zone (Klein et. al 2009:61-62).
The Los Pedroches region spans across an area about a third the size of the Ossa Morena Zone, and contains only forty-one known historic mines (Klein et. al 2009:61). Both Los Pedroches and
Ossa Morena appear to possess mining sites that potentially match the isotopic ratios of the lead sheathing, yet no single site stands out amongst all one hundred and forty three.
The first set of graphs (Figures 18 and 19) represents a comparison between the sheathing samples and the Ossa Morena Zone, initially omitting Los Pedroches so as to allow a gradual introduction of all comprehensive data sets from all predetermined regions. The second set of graphs (Figures 20 and 21) are essentially reproductions of the first, with scales adjusted to show, in detail, the proximity between the sheathing samples and any corresponding comparative ores.
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Lead Sheathing Samples/Ossa Morena Zone 39.2 39 38.8
38.6
38.4 38.2 Ossa Morena Zone 38
208Pb/204Pb Lead Sheathing Samples 37.8 37.6 37.4 37.2 15.45 15.5 15.55 15.6 15.65 15.7 15.75 207Pb/204Pb
Figure 18. Radiogenic and primeval ratio scatter plot of lead sheathing and Ossa Morena Zone
Lead Sheathing Samples/Ossa Morena Zone 2.18 2.16 2.14 2.12
2.1 2.08 2.06 Ossa Morena Zone
208Pb/206Pb 2.04 Lead Sheathing Samples 2.02 2 1.98 1.96 0.78 0.8 0.82 0.84 0.86 0.88 0.9 207Pb/206Pb
Figure 19. Radiogenic ratio scatter plot of lead sheathing and Ossa Morena Zone
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Lead Sheathing Samples/Ossa Morena Zone 38.44 38.435 38.43 38.425
38.42 Ossa Morena Zone 38.415 38.41 Lead Sheathing Samples 38.405 #418: Mina La Sultana 208Pb/204Pb 38.4 (15.629, 38.4102) 38.395 38.39 38.385 38.38 15.6 15.605 15.61 15.615 15.62 15.625 15.63 15.635 15.64 207Pb/204Pb
Figure 20. Radiogenic and primeval ratio scatter plot of lead sheathing and Ossa Morena Zone (scale adjusted for comparative analysis)
Lead Sheathing Samples/Ossa Morena Zone 2.09 2.089 2.088 2.087 2.086 2.085 2.084 2.083 2.082 Ossa Morena Zone
208Pb/206Pb 2.081 Lead Sheathing Samples 2.08 2.079 2.078 2.077 2.076 0.838 0.84 0.842 0.844 0.846 0.848 207Pb/206Pb
Figure 21. Radiogenic ratio scatter plot of lead sheathing and Ossa Morena Zone (scale adjusted for comparative analysis)
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Both the purely radiogenic graph and the radiogenic/primeval graph position the sheathing samples, represented by squares, within the swathe of comparative ore samples, represented by triangles. Note that while not necessarily buried within the most central cluster of mining sites, the sheathing samples undeniably rest inside the main assemblage of comparative ores.
Under close scrutiny, both the graphs with scales adjusted show the scattered sheathing samples deviating towards a single sample of ore. This single point represents the same ore sample in both graphs, a sample collected from a mine known as Mina La Sultana, originally identified in a study by Ortiz Hunt (2003) and listed as sample #418 in the comparative database
(Appendix D).
Attached to each graph are the approximate isotope ratios belonging to this single ore sample, all of which correspond relatively closely to the sheathing samples. However, it is entirely likely that ores from the Los Pedroches region exhibit similar, if not identical, proximities to the sheathing samples, dismissing the possibility of a positive association with
Mina La Sultana.
The similarities between the isotope ratios of the Ossa Morena Zone and Los Pedroches become apparent when plotting both regions on the same graphs. The Los Pedroches samples rise exponentially along the same path as those from the Ossa Morena Zone, demonstrating a similar ratio of radiogenic lead against primeval lead. In fact, in the Radiogenic/Primeval graph places the Los Pedroches samples group significantly higher than the main cluster from Ossa
Morena, and only slightly higher than the sheathing samples. While at a wider scale these samples appear to have a closer approximate distance to the sheathing samples upon closer
102 analysis (Figures 24 and 25) Mina La Sultana still possesses the strongest possible isotopic match.
The levels of radiogenic and primeval lead in Los Pedroches ore samples appear to correspond to that of the lead sheathing (Figures 22 and 23).The sheathing samples sit directly on top of the heaviest cluster of samples from Los Pedroches, indicating a closely matched series of isotope ratios. Yet, with adjusted scales and all outlying comparative samples removed from view, the sheathing samples once again bunch around a single point, that of Mina La Sultana.
Sample #418 appears to correspond remarkably well to the isotopic ratios from the lead sheathing, despite the introduction of a second sample set with relatively synonymous properties.
Graphical representation of the data presents undeniable patterns of correspondence, allowing for pinpoint accuracy when comparing all three samples. It is clear that both the purely radiogenic graphs and those involving primeval lead confirm that the likeliest source of the lead sheathing to be, in fact, Mina La Sultana.
However, it is crucial to note that the sheathing sample markers never completely overlap sample #418, but rather cluster around it, with some even located relatively far away. Enough deviation exists between the sheathing samples and sample #418, in fact, to suggest that they may not actually share a similar provenience. Nevertheless, given the proximity of the sheathing samples adjacent to #418, and the manner in which the scattered markers maintain a slight curve around the comparative sample, it seems that of all the comparative sites, Mina La Sultana stands as the most probable point of origin.
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Lead Sheathing Samples/Ossa Morena Zone/Los Pedroches 39.2 39 38.8
38.6 38.4 38.2 Ossa Morena Zone
38 Los Pedroches 208Pb/204Pb 37.8 Lead Sheathing Samples 37.6 37.4 37.2 15.45 15.5 15.55 15.6 15.65 15.7 15.75 207Pb/204Pb
Figure 22. Radiogenic and primeval ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region
Lead Sheathing Samples/Ossa Morena Zone/Los Pedroches 2.2
2.15
2.1
2.05 Ossa Morena Zone Los Pedroches 208Pb/206Pb 2 Lead Sheathing Samples
1.95
1.9 0.78 0.8 0.82 0.84 0.86 0.88 0.9 207Pb/206Pb
Figure 23. Radiogenic ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region
104
Lead Sheathing Samples/Ossa Morena Zone/Los Pedroches 38.48
38.45 Lead Sheathing Samples
38.42 Los Pedroches Region Ossa Morena 38.39
208Pb204Pb 38.36
38.33
38.3 15.6 15.61 15.62 15.63 15.64 207Pb/204Pb
Figure 24. Radiogenic and primeval ratio scatter plot of lead sheathing, Ossa Morena Zone, and Los Pedroches region (scale adjusted for comparative analysis)
Lead Sheathing Samples/Ossa Morena Zone/Los Pedroches 2.085
2.083
2.081 Ossa Morena Zone
2.079 Los Pedroches 208Pb/206Pb Lead Sheathing Samples 2.077
2.075 0.844 0.846 0.848 0.85 207Pb/206Pb
Figure 25. Radiogenic scatter plot of lead sheathing samples, Ossa Morena Zone, and Los Pedroches region (scale adjusted for comparative analysis)
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Statistically, there exists a less than 1% difference between the isotope ratios belonging to sample #418 and the isotope ratios from the lead sheathing (Table 1).
TABLE 1 AVERAGE VALUES OF LEAD SHEATHING AND MINA LA SULTANA ISOTOPE RATIOS
208Pb/204Pb 207Pb/204Pb 206Pb/204Pb 208Pb/206Pb 207Pb/206Pb Lead Sheathing 38.4184 15.626 18.471 2.07987 0.845 Samples Mina La 38.4102 15.629 18.474 2.07915 0.846 Sultana
Variation: .0082 .003 .003 .00072 .001
Similarity 99.97 99.98 99.98 99.96 99.88 (%)
The data from Mina La Sultana consist of six separate ores. While the sheathing samples possessed relatively similar isotopic ratios to sample #418, the other samples from Mina La
Sultana failed to align as closely. Without knowing specifically where each sample originated, a likely justification for the isotopic differences lie in the degree of distance between the comparative ore samples.
Early mining practices involved extending tunnels outwards from a wide, central pit for hundreds if not thousands of feet, depending on the direction and size of the chosen mineral deposit (Jones 1980:147-148). Some methods relied on crude subterranean shafts and tunnels; others used on holes dug down from the surface directly over a vein of ore, relying on deep exposed pits rather than underground channels (Jones 1980:146). The distance between the points of origin for all six comparative ore samples from Mina La Sultana is unknown, yet the
106 differences between each sample’s isotopic properties suggest they came from separate locations within the mine itself.
If the distance between samples in a single mine can indeed present researchers with differing isotopic values, then it is entirely possible that the thirty sheathing samples did in fact originate from this mine. It is impossible to determine the point of origin for the sheathing with pinpoint accuracy, given that all thirty samples failed to exactly match any comparative sample.
However, the fact that the isotopic ratios between the sheathing and a single ore sample differ by less than one percent not only confirms that the sheathing originated from Mina La Sultana, but that its extraction took place somewhere relatively adjacent to sample #418.
Nevertheless, based on the results of this test, it is clear that prior to the ill-fated voyage to Bahia Santa Maria de Ochuse, and even prior to leaving Spain, at least two of the vessels involved in the colonial attempt obtained hammered sheets of lead extracted from a mine located just northeast of Seville. Enough of the metal was transported from this single mine to cover (at least) two vessels up to their waterlines, each with lead cut into strips and arranged over their seams.
Unfortunately, a gap exists in the historical record regarding mining practices specifically in the Ossa Morena Zone between the period of Roman exploitation and the industrial revolution of the nineteenth century. According to research conducted by Klein et al. (2009:59-60), the
Ossa Morena Zone contains significant deposits of copper, silver and lead, and while it is known that various cultures and civilizations took advantage of these resources over the years, the details regarding their extraction, transportation, and subsequent utilization remain vague at best.
However, one can infer a few key factors concerning the area based on the geographic location of Mina La Sultana within the Ossa Morena Zone. For instance, Mina La Sultana lies
107 directly north of the Guadalquivir River (Figure 26). One of the most commercially successful and agriculturally bountiful regions in southern Spain, the surrounding Guadalquivir Valley had both waterways and a sophisticated network of roads (O’Flanagan 2008:42). These systems of transportation flowed west, passing through Seville and eventually running out to the Atlantic
Ocean. Seville, one of the largest and most populated trading cities in Spain, monopolized trade throughout the Iberian Peninsula, and possessed a port through which all goods, imported or exported, were required to pass (O’Flanagan 2008:43-44). While a mine like Los Pedroches, located further up the Guadalquivir River, produced copious amounts of raw metal, it was certainly more convenient for craftsmen to use lead extracted from a proximate source.
Figure 26. Locations of Mina La Sultana in Relation to Known Ore Deposits of Southern Spain (Adapted from Klein et al. 2009:61. Location of Mina La Sultana from Tornos et al. 2004:146)
Discovering the source of the lead sheathing on the Emanuel Point vessels opens up an infinite number of additional avenues for research. For instance, while we now know that both
Emanuel Point ships received sheathing from a single mine, we do not know: (a) the amounts of lead ore produced by this single mine; (b) whether shipyards used lead exclusively from this 108 mine; (c) whether this was one of the largest suppliers of lead to Seville; or (d) whether the fact that both Emanuel Point vessels possessed lead from this mine was merely a coincidence. Any subsequent research on this topic could potentially go a variety of different directions, from the economic to the industrial. Fortunately, through the use of lead isotope analysis, the source of the lead sheathing no longer remains a mystery.
109
CHAPTER VII
SUMMARY AND CONCLUSIONS
The advancement of naval technology directly attributed to the Iberian expansion of the fifteenth and sixteenth centuries. Exploration brought about the need for large sea going vessels capable of transporting tons of cargo and crew around the world, which in turn resulted in the development of protective safety measures capable of preserving ships for the duration of transoceanic voyages. The rapid growth of this international empire directly resulted in the vast employment of lead for most, if not all, seagoing vessels at the time.
This thesis focused specifically on the sheathing fragments recovered from the Emanuel
Point shipwrecks in Pensacola Bay; two vessels originally associated with the 1559 colonization attempt lead by Tristán de Luna y Arellano. Built in Spain, these ships represent a tangible example of sixteenth-century naval architecture, and possess a history that far exceeds their ill- fate expedition to Bahia Santa Maria de Ochuse. Information on these vessels’ prior voyages remains unknown, although ongoing efforts by students and professionals alike continuously paint a broader and more informative picture (Lawrence 2010; Worth 2009).
Each section of this study, while individually illuminative, builds on the previous, and the culmination of data from each chapter provides the basis from which this author derived a hypothesis on the origin of the lead itself. As stated in the introduction, this thesis aimed to answer three main questions regarding the sheathing from the Emanuel Point vessels. These were: (a) to what degree did the lead cover the vessels below the waterline, (b) would the sheathing have endured a transatlantic voyage without the need for replacement, and (c) did the lead originate from mines in the Old World or the New?
110
Given the scarcity of lead on either site, and the strip-like shape of the metal itself, evidence from both the first and second Emanuel Point wrecks indicates that the sheathing provided only partial protection along the hull. Partial protection was likely due to the heavy and expensive nature of the lead, enough of which would weigh down the already overloaded ships and hinder their progress as they sailed to Pensacola. While such a practice would inevitably result in the overwhelming infestation of teredo worms, it is unknown exactly how long Luna intended for these vessels to endure after the colonial expedition.
By way of experimentation, this study answered the question regarding lead’s longevity.
After a six-month submersion in Pensacola Bay, a series of wrought iron tacks, similar in design to those used to nail the lead to hulls of the Emanuel Point ships, underwent a 15% reduction in mass. Nailed over strips of lead, these tacks corroded at an accelerated rate, a common problem amongst contemporaneous vessels using metals with opposing ionic properties for hull sheathing. Though 15% is significant, the reduction affected only the very surface of the tack heads, rather than the more structurally significant areas. This loss would hardly affect the fundamental integrity of the tacks, and thus suggests that they, and the sheathing beneath, lasted the duration of an average transatlantic journey (two to four months, depending on the time of year).
Hypothetically, should this rate of corrosion persist, a year’s worth of exposure implies a
30% loss in mass; two years implies a 60% loss, and so on. However, too many variables exist to predict this with complete accuracy. In fact, while this experiment attempts to address the scientific nature of the tacks’ longevity, it is by no means conclusive, as a number of environmental and physical factors certainly played a role in the loss of hull sheathing over time.
Nevertheless, from a purely scientific standpoint it seems plausible that, given calm conditions,
111 the tacks could not only endure the journey to the New World, but possibly even the journey back; therefore there was no need to replace lead in the New World.
Assuming that the lead did indeed survive the transatlantic voyage, and that most vessels arriving at Vera Cruz at this time possessed similarly unaffected sheathing, it seems unlikely that sailors required a plentiful supply of lead at colonial ports. New Spain’s infrastructure at the time relied on agriculture and precious metals, and while lead was a byproduct of the amalgamation process used to extract silver from raw ore, it remains unknown whether colonists used it in any large-scale capacity. These and other factors suggest that any lead used for the purpose of sheathing likely originated in the Iberian Peninsula.
Using lead isotope analysis, this study attempted to answer the question of the lead’s provenience. Fifteen samples from each wreck, recovered from various locations around each site, underwent isotopic analysis using a multiple-collector inductively coupled plasma mass spectrometer to determine their isotopic ratios. All thirty samples displayed similar characteristics, suggesting a specific point of origin. However, these results fail to indicate a geographic provenience; only that both wrecks possessed sheathing from the same source.
Determining a point of origin required comparing the isotope ratios of the lead sheathing against hundreds of ore samples from historic Spanish mines. After extensive comparisons, the samples matched those of a mine named Mina La Sultana, a copper-lead-silver mine located within the heart of a major ore deposit known as the Ossa Morena Zone in southern Spain. While little knowledge exists regarding Mina La Sultana, its proximity to Seville, one of the largest seaports in Spain, makes it a likely candidate as the source of lead for the manufacture of ship’s sheathing. Graphical and statistical comparisons confirmed that less than a 1% difference exists
112 between the sheathing samples and those from Mina La Sultana, confirming that the lead did indeed originate in extremely close proximity to this mine.
While the samples used in this thesis originate solely from the two Emanuel Point vessels, the tests, and their subsequent results, may apply to any similar studies on Iberian sheathing practices. For instance, the results of the tack corrosion test may provide a basis from which one can interpret the longevity of similarly sized iron components, and any studies on
Iberians lead sources may use the results of the lead isotope analysis in this test for comparison.
A wealth of knowledge regarding the 1559 colonization of Bahia Santa Maria de Ochuse arose after investigations of the shipwrecks began in 1992, and, as time goes on, excavations continue to reveal more information. With the history of the Luna expedition well established, current research tends to focus on specific artifact assemblages associated with the wrecks rather than the voyage itself, revealing a broader and yet somewhat focused perspective on various aspects of the Spanish world at the time. For instance, recent studies on the floral and faunal remains found aboard the Emanuel Point vessels provide a wealth of knowledge regarding the types of foodstuffs brought with the colonists, and examines whether the Luna expedition played a role in introducing non-native species of plants and insects to North America. By incorporating studies from disciplines outside of archeology, such as botany and osteology for instance, these studies use the artifacts to tell another side to the story of the Luna expedition.
This comprehensive investigation of lead sheathing provides yet another angle to the story, one that observes a characteristic of the ship itself, rather than a constituent of its cargo.
Strategically placed so as to protect the caulking from teredo damage, these strips of lead represented the pinnacle of sheathing technology at the time, and they apparently served their purpose well. Having provided adequate protection for these vessels across the Atlantic and even
113 into Pensacola Bay it is entirely possible that, were it not for the unexpected hurricane that devastated the 1559 fleet, the lead might have survived well beyond this final voyage.
Nevertheless, the information acquired from these remains provides yet another unique perspective on the ships used in the ill-fated Luna expedition, and the complexities of Spanish seafaring technology in the sixteenth century.
114
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APPENDIXES
126
Appendix A
Tack Weights and Measurements for Sheathing Experiment
127
Tack Model Date Date Starting Weight Final Weight Total Loss Total Loss (%) # Submerged Removed (g) (g) (g) 1 Sabine Island 7/26/2010 2/3/2011 12.4 10.3 2.1 0.161290323 2 Sabine Island 7/26/2010 2/3/2011 12.4 10.2 2.2 0.241935484 3 Sabine Island 7/26/2010 2/3/2011 12.1 9.7 2.4 0.247933884 4 Sabine Island 7/26/2010 2/3/2011 12 10.8 1.2 0.25 5 Sabine Island 7/26/2010 2/3/2011 12.6 9.9 2.7 0.238095238 6 Sabine Island 7/26/2010 2/3/2011 12.8 9.7 3.1 0.234375 7 Sabine Island 7/26/2010 2/3/2011 12.3 9.9 2.4 0.243902439 8 Sabine Island 7/26/2010 2/3/2011 12.6 10.5 2.1 0.238095238 9 Sabine Island 7/26/2010 2/3/2011 11.9 8.6 3.3 0.25210084 10 Sabine Island 7/26/2010 2/3/2011 13.2 11.3 1.9 0.227272727 11 Sabine Island 7/26/2010 2/3/2011 13.5 11.5 2 0.222222222 12 Sabine Island 7/26/2010 2/3/2011 12.9 10.5 2.4 0.23255814 13 Sabine Island 7/26/2010 2/3/2011 12.6 10.1 2.5 0.238095238 14 Sabine Island 7/26/2010 2/3/2011 13.1 9.3 3.8 0.229007634 15 Sabine Island 7/26/2010 2/3/2011 12.4 11.6 0.8 0.241935484 16 Sabine Island 7/26/2010 2/3/2011 11.7 11.5 0.2 0.256410256 17 Sabine Island 7/26/2010 2/3/2011 13.1 10.8 2.3 0.229007634 18 Sabine Island 7/26/2010 2/3/2011 12.1 8.9 3.2 0.247933884
19 Sabine Island 7/26/2010 2/3/2011 12 11 1 0.25
Tack Model Date Date Starting Weight Final Weight Total Loss Total Loss (%) # Submerged Removed (g) (g) (g)
20 Sabine Island 7/26/2010 2/3/2011 11.8 10.5 1.3 0.254237288 21 Sabine Island 7/26/2010 2/3/2011 12.1 10 2.1 0.247933884 22 Sabine Island 7/26/2010 2/3/2011 11.7 9.9 1.8 0.256410256 23 Sabine Island 7/26/2010 2/3/2011 11.3 10.5 0.8 0.265486726 24 Sabine Island 7/26/2010 2/3/2011 12.3 8.9 3.4 0.243902439 25 Sabine Island 7/26/2010 2/3/2011 12.5 8.9 3.6 0.24 26 Sabine Island 7/26/2010 2/3/2011 12.8 11 1.8 0.234375 27 Sabine Island 7/26/2010 2/3/2011 13.4 10.2 3.2 0.223880597 28 Sabine Island 7/26/2010 2/3/2011 13.2 11.4 1.8 0.227272727 29 Sabine Island 7/26/2010 2/3/2011 12.8 12.1 0.7 0.234375 30 Sabine Island 7/26/2010 2/3/2011 12.4 11.3 1.1 0.241935484 31 Sabine Island 7/26/2010 2/3/2011 12.3 10 2.3 0.243902439 32 Sabine Island 7/26/2010 2/3/2011 12.9 11.4 1.5 0.23255814 33 Sabine Island 7/26/2010 2/3/2011 12.5 11.3 1.2 0.24 34 Sabine Island 7/26/2010 2/3/2011 12.3 11.2 1.1 0.243902439 35 Sabine Island 7/26/2010 2/3/2011 11.3 10.4 0.9 0.265486726 36 Sabine Island 7/26/2010 2/3/2011 14.1 12.8 1.3 0.212765957 37 Sabine Island 7/26/2010 2/3/2011 12.3 11.4 0.9 0.243902439 38 Sabine Island 7/26/2010 2/3/2011 11.9 10.9 1 0.25210084
Tack Model Date Date Starting Weight Final Weight Total Loss Total Loss (%) # Submerged Removed (g) (g) (g)
1 EPII Ballast 7/20/2010 2/15/2011 12.2 10.1 2.1 0.172131148 2 EPII Ballast 7/20/2010 2/15/2011 12 10.6 1.4 0.116666667 3 EPII Ballast 7/20/2010 2/15/2011 12.5 10.9 1.6 0.128 4 EPII Ballast 7/20/2010 2/15/2011 12.4 9.7 2.7 0.217741935 5 EPII Ballast 7/20/2010 2/15/2011 12.2 10.6 1.6 0.131147541 6 EPII Ballast 7/20/2010 2/15/2011 12.4 10 2.4 0.193548387 7 EPII Ballast 7/20/2010 2/15/2011 13.1 10.2 2.9 0.221374046 8 EPII Ballast 7/20/2010 2/15/2011 12.2 11.1 1.1 0.090163934 9 EPII Ballast 7/20/2010 2/15/2011 11.9 9.5 2.4 0.201680672 10 EPII Ballast 7/20/2010 2/15/2011 12.8 9.2 3.6 0.28125 11 EPII Ballast 7/20/2010 2/15/2011 13.2 10.2 3 0.227272727 12 EPII Ballast 7/20/2010 2/15/2011 12.9 10.3 2.6 0.201550388 13 EPII Ballast 7/20/2010 2/15/2011 12.5 11.1 1.4 0.112 14 EPII Ballast 7/20/2010 2/15/2011 12.4 10.1 2.3 0.185483871 15 EPII Ballast 7/20/2010 2/15/2011 13.2 11.4 1.8 0.136363636 16 EPII Ballast 7/20/2010 2/15/2011 13.2 12.1 1.1 0.083333333 17 EPII Ballast 7/20/2010 2/15/2011 12.6 11.2 1.4 0.111111111 18 EPII Ballast 7/20/2010 2/15/2011 12.2 10.3 1.9 0.155737705 19 EPII Ballast 7/20/2010 2/15/2011 12.4 10.7 1.7 0.137096774
Tack Model Date Date Starting Weight Final Weight Total Loss Total Loss (%) # Submerged Removed (g) (g) (g)
20 EPII Ballast 7/20/2010 2/15/2011 12.4 10.3 2.1 0.169354839 21 EPII Ballast 7/20/2010 2/15/2011 12.3 11.7 0.6 0.048780488 22 EPII Ballast 7/20/2010 2/15/2011 12.4 10.4 2 0.161290323 23 EPII Ballast 7/20/2010 2/15/2011 13.1 11 2.1 0.160305344 24 EPII Ballast 7/20/2010 2/15/2011 12.7 10.5 2.2 0.173228346 25 EPII Ballast 7/20/2010 2/15/2011 12.8 11.4 1.4 0.109375 26 EPII Ballast 7/20/2010 2/15/2011 12.6 11.3 1.3 0.103174603 27 EPII Ballast 7/20/2010 2/15/2011 12.9 11.1 1.8 0.139534884 28 EPII Ballast 7/20/2010 2/15/2011 11.9 10.4 1.5 0.12605042 29 EPII Ballast 7/20/2010 2/15/2011 12.8 9.8 3 0.234375 30 EPII Ballast 7/20/2010 2/15/2011 13.1 10.4 2.7 0.20610687 31 EPII Ballast 7/20/2010 2/15/2011 13.7 13.2 0.5 0.123255814 32 EPII Ballast 7/20/2010 2/15/2011 12 11.3 0.7 0.058333333 33 EPII Ballast 7/20/2010 2/15/2011 12.7 12 0.7 0.05511811 34 EPII Ballast 7/20/2010 2/15/2011 12.2 11.4 0.8 0.06557377 35 EPII Ballast 7/20/2010 2/15/2011 12.5 10.9 1.6 0.128 36 EPII Ballast 7/20/2010 2/15/2011 13.2 11.1 2.1 0.159090909 37 EPII Ballast 7/20/2010 2/15/2011 11.7 10 1.7 0.145299145 38 EPII Ballast 7/20/2010 2/15/2011 11.6 10.2 1.4 0.120689655
Tack Model Date Date Starting Weight Final Weight Total Loss Total Loss (%) # Submerged Removed (g) (g) (g)
39 EPII Ballast 7/20/2010 2/15/2011 11.9 10.1 1.8 0.151260504 40 EPII Ballast 7/20/2010 2/15/2011 12.3 11.1 1.2 0.097560976 41 EPII Ballast 7/20/2010 2/15/2011 12.4 11.2 1.2 0.096774194 42 EPII Ballast 7/20/2010 2/15/2011 11.8 10.2 1.6 0.13559322 43 EPII Ballast 7/20/2010 2/15/2011 12.4 10.5 1.9 0.153225806 44 EPII Ballast 7/20/2010 2/15/2011 11.5 10.4 1.1 0.095652174 45 EPII Ballast 7/20/2010 2/15/2011 11.9 10.3 1.6 0.134453782 46 EPII Ballast 7/20/2010 2/15/2011 13.2 11.7 1.5 0.113636364 47 EPII Ballast 7/20/2010 2/15/2011 11.5 10 1.5 0.130434783 48 EPII Ballast 7/20/2010 2/15/2011 11.3 10.6 0.7 0.061946903 49 EPII Ballast 7/20/2010 2/15/2011 11.7 9.4 2.3 0.196581197 50 EPII Ballast 7/20/2010 2/15/2011 11.4 9.7 1.7 0.149122807 51 EPII Ballast 7/20/2010 2/15/2011 13.2 11.3 1.9 0.143939394 52 EPII Ballast 7/20/2010 2/15/2011 12.7 11.4 1.3 0.102362205 53 EPII Ballast 7/20/2010 2/15/2011 12.3 11 1.3 0.105691057 54 EPII Ballast 7/20/2010 2/15/2011 12.2 10.3 1.9 0.155737705 55 EPII Ballast 7/20/2010 2/15/2011 12.5 9.7 2.8 0.224 56 EPII Ballast 7/20/2010 2/15/2011 11.6 10.3 1.3 0.112068966 57 EPII Ballast 7/20/2010 2/15/2011 11.8 10.2 1.6 0.13559322
Tack Model Date Date Starting Weight Final Weight Total Loss Total Loss (%) # Submerged Removed (g) (g) (g)
58 EPII Ballast 7/20/2010 2/15/2011 11.6 10.8 0.8 0.068965517 59 EPII Ballast 7/20/2010 2/15/2011 11.9 9.5 2.4 0.201680672
Appendix B
XRF Analysis of Lead Sheathing Samples
134 Sample # Site Artifact # Fe Fe +/- Zn Zn +/- Zr Zr +/- Sn Sn +/- W W +/- Pb Pb +/-
1 8ES1980 EPI-00003 0.1 0.03 ND ND ND ND 99.9 0.34
2 8ES1980 EPI-00107 1.92 0.07 ND ND ND ND 98.08 0.35
3 8ES1980 EPI-00427 0.37 0.04 ND ND ND 0.32 0.09 99.31 0.4
0.2 4 8ES1980 EPI-00651 0.2 0.03 ND ND 0.03 ND 99.58 0.34 2 5 8ES1980 EPI-00685 0.22 0.04 ND ND ND ND 99.78 0.37
6 8ES1980 EPI-01123 1.47 0.06 ND ND ND ND 98.53 0.36
0.0 7 8ES1980 EPI-01397 14.38 0.15 ND ND 0.02 ND 85.54 0.3 8 8 8ES1980 EPI-01558 0.11 0.03 ND ND ND ND 99.89 0.36
9 8ES1980 EPI-01561 ND ND ND ND ND 100 0.37
10 8ES1980 EPI-00441 2.15 0.08 ND ND ND 0.39 0.09 97.46 0.38
0.1 11 8ES1980 EPI-00582 0.13 0.03 ND ND 0.03 ND 99.74 0.34 2 12 8ES1980 EPI-02322 0.43 0.04 ND ND ND ND 99.57 0.36
13 8ES1980 EPI-00600 4.36 0.09 ND 0.06 0.01 ND 1.08 0.1 94.5 0.35
14 8ES1980 EPI-02275 1.61 0.07 ND ND ND ND 98.39 0.39
15 8ES1980 EPI-02543 1.91 0.06 ND ND 0.1 0.03 ND 97.9 0.34
Sample # Site Artifact # Fe Fe +/- Zn Zn +/- Zr Zr +/- Sn Sn +/- W W +/- Pb Pb +/-
16 8ES3345 EPII-0097 3.04 0.09 ND ND ND ND 96.96 0.39
17 8ES3345 EPII-1535 1.55 0.06 0.12 0.01 ND 0.29 0.03 ND 98.04 0.37
18 8ES3345 EPII-0673 0.24 0.04 ND ND ND ND 99.76 0.39
19 8ES3345 EPII-1096 0.71 0.05 ND ND ND ND 99.29 0.37
20 8ES3345 EPII-0569 0.84 0.05 ND ND 0.29 0.03 ND 98.86 0.39
21 8ES3345 EPII-0696 0.92 0.05 ND ND 0.22 0.03 ND 98.86 0.37
22 8ES3345 EPII-0703 ND ND ND 0.11 0.03 ND 99.89 0.38
23 8ES3345 EPII-2041 0.27 0.04 ND ND 0.13 0.03 ND 99.6 0.38
24 8ES3345 EPII-1086 0.42 0.04 ND ND ND ND 99.58 0.39
25 8ES3345 EPII-1776 0.22 0.03 ND ND 0.16 0.03 ND 99.61 0.36
26 8ES3345 EPII-1791 3.6 0.11 ND 0.12 0.01 0.18 0.05 ND 96.11 0.42
27 8ES3345 EPII-0564 ND ND ND 0.21 0.03 ND 99.79 0.35
28 8ES3345 EPII-0698 0.58 0.04 ND ND 0.11 0.03 ND 99.31 0.35
29 8ES3345 EPII-2835 0.14 0.03 ND ND 0.17 0.02 ND 99.69 0.34
30 8ES3345 EPII-2382 ND ND ND ND ND 100 0.34
Appendix C
MC-ICPMS Results of Lead Sheathing Isotope Analysis
137 Sample # Artifact # 208/204 207/204 206/204 208/206 207/206
1 EPI-00003 38.40995 15.62672 18.46587 2.080022 0.846261
2 EPI-00107 38.41073 15.6223 18.45585 2.081129 0.846475
3 EPI-00427 38.40848 15.62673 18.46631 2.079903 0.846223
4 EPI-00651 38.42576 15.62651 18.47458 2.079953 0.845843
5 EPI-00685 38.41596 15.62736 18.47036 2.079884 0.846069
6 EPI-01123 38.41562 15.62558 18.47194 2.079698 0.845917
7 EPI-01397 38.41254 15.62522 18.4726 2.079467 0.845854
8 EPI-01558 38.41872 15.62875 18.47175 2.079882 0.846077
9 EPI-01561 38.4116 15.62517 18.46773 2.079935 0.846059
10 EPI-00441 38.41987 15.62715 18.47474 2.079611 0.845878
11 EPI-00582 38.41957 15.62888 18.47231 2.079873 0.846072
12 EPI-02322 38.41202 15.62497 18.46833 2.079939 0.846061
13 EPI-00600 38.41631 15.62943 18.47023 2.07992 0.846191
14 EPI-02275 38.43475 15.62744 18.48502 2.079198 0.845417
15 EPI-02543 38.4098 15.62529 18.46819 2.079857 0.846065
Sample # Artifact # 208/204 207/204 206/204 208/206 207/206
16 EPII-0097 38.43419 15.63363 18.48453 2.079252 0.845763
17 EPII-1535 38.41717 15.62718 18.46972 2.080039 0.846103
18 EPII-0673 38.41857 15.62758 18.46992 2.080012 0.846094
19 EPII-1096 38.41078 15.62398 18.46934 2.079699 0.845934
20 EPII-0569 38.40649 15.62278 18.46641 2.079844 0.846016
21 EPII-0696 38.41954 15.62734 18.46859 2.080249 0.846153
22 EPII-0703 38.41974 15.62907 18.47183 2.079914 0.846091
23 EPII-2041 38.43279 15.62705 18.47922 2.07977 0.845653
24 EPII-1086 38.41883 15.62872 18.47148 2.07988 0.846084
25 EPII-1776 38.41785 15.62829 18.47175 2.079809 0.846049
26 EPII-1791 38.41692 15.62801 18.47155 2.07974 0.846043
27 EPII-0564 38.4339 15.6256 18.47894 2.079869 0.84559
28 EPII-0698 38.4244 15.62619 18.47282 2.080071 0.845897
29 EPII-2835 38.42455 15.6247 18.47311 2.080008 0.845807
30 EPII-2382 38.41747 15.62594 18.47184 2.079792 0.845955
Appendix D
Ossa Morena Zone and Los Pedroches Comparative Data
140 ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Mina La Ossa 418 18.474 15.629 38.4102 0.846 2.07915 Hunt 2003 Sultana Morena Mina La Ossa 419 18.341 15.5414 38.1931 0.84736 2.08239 Hunt 2003 Sultana Morena Mina La Ossa 420 18.365 15.6367 38.4183 0.85144 2.09193 Hunt 2003 Sultana Morena Mina La Ossa 421 18.311 15.6248 38.2625 0.8533 2.08959 Hunt 2003 Sultana Morena Mina La Ossa 422 18.503 15.6637 38.6206 0.84655 2.08726 Hunt 2003 Sultana Morena Mina La Ossa 423 18.911 15.6343 38.4886 0.82673 2.03525 Hunt 2003 Sultana Morena Tornos y Santa Ana Ossa 1 SANA–1 17.707 15.539 37.808 0.8775625 2.135201 Chiarada (MaLuisa) Morena 2004
Tornos y Santa Ana Ossa 2 SANA–11 17.684 15.509 37.714 0.8770075 2.132662 Chiarada (MaLuisa) Morena 2004 Tornos y Ossa 3 Maria Luisa ML–1 17.511 15.492 37.477 0.8847011 2.140198 Chiarada Morena 2004 Tornos y Ossa 4 Maria Luisa 2 17.491 15.47 37.406 0.8844548 2.138586 Chiarada Morena 2004 Tornos y Ossa 5 Maria Luisa 2 17.503 15.485 37.499 0.8847055 2.142433 Chiarada Morena 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Tornos y Ossa 6 Puebla Reina 209–9 17.874 15.633 37.641 0.8746223 2.105908 Chiarada Morena 2004 Tornos y Ossa 7 Puebla Reina 209–10 17.856 15.622 37.608 0.874888 2.106183 Chiarada Morena 2004 Tornos y Ossa 8 Puebla Reina PR–2 17.747 15.542 37.449 0.8757536 2.110159 Chiarada Morena 2004 Tornos y Ossa 9 Puebla Reina 2 17.814 15.577 37.372 0.8744246 2.097901 Chiarada Morena 2004 Tornos y Ossa 10 Puebla Reina 2 17.819 15.587 37.404 0.8747404 2.099108 Chiarada Morena 2004 Tornos y Ossa 11 Aracena AR–7 17.555 15.543 37.778 0.8853888 2.151979 Chiarada Morena 2004 Tornos y Ossa 12 Aracena AR–8 17.517 15.5 37.634 0.8848547 2.148427 Chiarada Morena 2004 Tornos y Ossa 13 Aracena AR–8a 17.551 15.546 37.785 0.8857615 2.152869 Chiarada Morena 2004 Tornos y Fuenteheridos Ossa 14 17.539 15.531 37.637 0.8855123 2.145903 Chiarada 2 Morena 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Tornos y Ossa 15 Las Minas LM–1 17.568 15.51 37.698 0.8828552 2.145833 Chiarada Morena 2004 Tornos y Ossa 16 Las Minas LM–2 17.577 15.512 37.712 0.8825169 2.145531 Chiarada Morena 2004 Tornos y Ossa 17 Retín 219–5 17.767 15.646 38.249 0.8806214 2.152811 Chiarada Morena 2004 Tornos y Ossa 18 Retín 219–6 17.805 15.666 38.312 0.8798652 2.151755 Chiarada Morena 2004 Tornos y Ossa 19 Nava-aredón PAR–1 17.95 15.57 38.181 0.8674095 2.127075 Chiarada Morena 2004 Tornos y Ossa 20 Nava-aredón N–13A 17.931 15.554 38.031 0.8674363 2.120964 Chiarada Morena 2004 Tornos y Ossa 21 Nava-aredón N–18 17.959 15.561 38.079 0.8664736 2.12033 Chiarada Morena 2004 Tornos y Ossa 22 Nava-aredón NP–1 17.927 15.542 38.095 0.8669605 2.125007 Chiarada Morena 2004 Tornos y Ossa 23 Nava-aredón 2 17.921 15.555 38.018 0.8679761 2.121422 Chiarada Morena 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Tornos y Ossa 24 La Hinchona HI–1 18.073 15.588 38.251 0.8625021 2.116472 Chiarada Morena 2004 Tornos y Ossa 25 La Hinchona HI–2 18.046 15.554 38.148 0.8619084 2.113931 Chiarada Morena 2004 Tornos y El Aguila Ossa 26 68–72–1 18.147 15.553 38.245 0.8570563 2.107511 Chiarada (Monesterio) Morena 2004 Tornos y El Nogalito Ossa 27 68–49–1 18.123 15.556 38.253 0.8583568 2.110743 Chiarada (Monesterio) Morena 2004 Tornos y El Aguilar Ossa 28 68–51–1 18.097 15.531 38.134 0.8582085 2.1072 Chiarada (Monesterio) Morena 2004 Tornos y Ossa 29 Colmenar S–300 18.132 15.562 38.234 0.8582616 2.108648 Chiarada Morena 2004 Tornos y Ossa 30 Aguablanca AG–5 17.935 15.602 38.232 0.8699192 2.131698 Chiarada Morena 2004 Tornos y Ossa 31 Aguablanca AG–18 18.054 15.576 38.252 0.8627451 2.118755 Chiarada Morena 2004 Tornos y Ossa 32 Aguablanca 2 18.055 15.566 38.159 0.8621435 2.113487 Chiarada Morena 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Tornos y Ossa 33 Aguablanca 2 18.068 15.567 38.174 0.8615785 2.112796 Chiarada Morena 2004 Tornos y Ossa 34 Abundancia AB–2 18.269 15.605 38.387 0.8541792 2.10121 Chiarada Morena 2004 Tornos y Ossa 35 Abundancia AB–6 18.425 15.645 38.615 0.8491181 2.095794 Chiarada Morena 2004 Tornos y Ossa 36 Sultana SU–10 18.296 15.617 38.534 0.8535746 2.106143 Chiarada Morena 2004 Tornos y Ossa 37 Sultana SU–21 18.438 15.627 38.782 0.8475431 2.103374 Chiarada Morena 2004 Tornos y Ossa 38 Matachel 248–4 17.965 15.654 38.434 0.871361 2.139382 Chiarada Morena 2004 Tornos y Ossa 39 San Nicolás SN–3 18.317 15.589 38.463 0.8510673 2.099853 Chiarada Morena 2004 Tornos y Ossa 40 San Nicolás SN–4 18.278 15.587 38.404 0.8527738 2.101105 Chiarada Morena 2004 Tornos y Ossa 41 Espiel ESP–1 18.398 15.632 38.46 0.8496576 2.090445 Chiarada Morena 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Tornos y Ossa 42 Oropesa OR–1 18.202 15.63 38.513 0.8586968 2.115866 Chiarada Morena 2004 Tornos y Ossa 43 Oropesa OR–2 18.176 15.634 38.485 0.8601453 2.117352 Chiarada Morena 2004 Tornos y Ossa 44 Santa Marta SM–1 18.216 15.55 38.172 0.8536451 2.09552 Chiarada Morena 2004 Tornos y Ossa 45 Santa Marta SM–1a 18.229 15.567 38.229 0.853969 2.097153 Chiarada Morena 2004 Tornos y Ossa 46 Santa Marta SM–2 18.166 15.571 38.203 0.8571507 2.102995 Chiarada Morena 2004 Tornos y Ossa 47 Santa Marta SM–2b 18.146 15.546 38.125 0.8567177 2.101014 Chiarada Morena 2004 Tornos y Ossa 48 Afortunada 213–2 18.159 15.611 38.407 0.8596839 2.115039 Chiarada Morena 2004 Tornos y Ossa 49 Afortunada 213–10 18.158 15.607 38.395 0.859511 2.114495 Chiarada Morena 2004 Tornos y Ossa 50 Afortunada 213–10a 18.136 15.578 38.3 0.8589545 2.111822 Chiarada Morena 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Tornos y Ossa 51 Arroyo Conejo 215–4 18.2 15.596 38.43 0.8569231 2.111538 Chiarada Morena 2004 Tornos y Ossa 52 Arroyo Conejo 215–4a 18.209 15.606 38.459 0.8570487 2.112087 Chiarada Morena 2004 Ossa según 395 La Dehesa 18.275 15.6937 38.5942 0.85875 2.11186 Morena NIST Ossa según 396 La Dehesa 18.166 15.6169 38.3606 0.85968 2.11167 Morena NIST Ossa según 397 La Dehesa 18.251 15.6798 38.5702 0.85912 2.11332 Morena NIST Ossa según 398 La Dehesa 18.216 15.6572 38.523 0.85953 2.11479 Morena NIST Ossa según 399 La Dehesa 18.162 15.6119 38.3512 0.85959 2.11162 Morena NIST Ossa según 400 La Dehesa 18.158 15.6066 38.3392 0.85949 2.11142 Morena NIST Mina Santa Ossa 417 Barbara 18.2116 15.591 38.1733 0.8561 2.0961 Hunt 2003 Morena (Posadas, CO MINAS DE Ossa 434 CALA 18.795 15.6737 38.782 0.83393 2.06342 Hunt 2003 Morena (DOLORES) MINAS DE Ossa 435 CALA 18.595 15.6665 38.3884 0.84251 2.06445 Hunt 2003 Morena (DOLORES)
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
MINAS DE Ossa 436 CALA 18.438 15.6788 38.4405 0.85035 2.08485 Hunt 2003 Morena (DOLORES) MINAS DE Ossa 437 CALA 18.701 15.6909 38.9306 0.83904 2.08174 Hunt 2003 Morena (DOLORES) MINAS DE Ossa 438 CALA 19.059 15.6661 38.2691 0.82198 2.00793 Hunt 2003 Morena (DOLORES) MINA Ossa 439 18.654 15.6671 38.5162 0.83988 2.06477 Hunt 2003 TEULER Morena MINA Ossa 440 18.926 15.6618 38.4236 0.82753 2.0302 Hunt 2003 TEULER Morena MINA Ossa 441 18.496 15.6332 38.2477 0.84522 2.06789 Hunt 2003 TEULER Morena MINA Ossa 442 19.573 15.6948 38.6177 0.80186 1.97301 Hunt 2003 TEULER Morena Santos Ossa 1479 Azuaga N BA-1 18.18 15.59 38.29 0.85754 2.10616 Zalduegui Morena et al 2007 Santos Ossa 1480 Azuaga N BA-2 18.163 15.587 38.282 0.85817 2.10769 Zalduegui Morena et al 2007 Santos Ossa 1481 Azuaga N BA-3 18.14 15.58 38.26 0.85888 2.10915 Zalduegui Morena et al 2007
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Santos Ossa 1482 Azuaga N BA-4 18.184 15.612 38.365 0.85856 2.10982 Zalduegui Morena et al 2007 Santos Ossa 1483 Azuaga N BA-5 18.21 15.625 38.394 0.85805 2.1084 Zalduegui Morena et al 2007 Santos Ossa 1484 Azuaga N BA-6 18.172 15.595 38.331 0.85819 2.10934 Zalduegui Morena et al 2007 Santos Ossa 1485 Azuaga N BA-7 18.174 15.602 38.346 0.85848 2.10994 Zalduegui Morena et al 2007 Santos Ossa 1486 Azuaga N BA-8 18.153 15.597 38.328 0.8592 2.11139 Zalduegui Morena et al 2007 Santos Ossa 1487 Azuaga N BA-8b 18.152 15.595 38.322 0.85913 2.11117 Zalduegui Morena et al 2007 Santos Ossa 1488 Azuaga N BA-9 18.165 15.607 38.383 0.85918 2.11302 Zalduegui Morena et al 2007 Santos Ossa 1489 Azuaga N BA-10 18.181 15.611 38.406 0.85864 2.11243 Zalduegui Morena et al 2007 Santos Ossa 1490 Azuaga S BA-11 18.15 15.594 38.347 0.85917 2.11278 Zalduegui Morena et al 2007
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Santos Ossa 1491 Azuaga S BA-12 18.146 15.589 38.339 0.85909 2.11281 Zalduegui Morena et al 2007 Santos Ossa 1492 Azuaga S BA-13 18.152 15.602 38.356 0.85952 2.11305 Zalduegui Morena et al 2007 Santos Ossa 1493 Azuaga S BA-14 18.13 15.588 38.301 0.85979 2.11258 Zalduegui Morena et al 2007 Santos Ossa 1494 Azuaga S BA-15 18.139 15.596 38.32 0.8598 2.11258 Zalduegui Morena et al 2007 Santos Ossa 1495 Azuaga S BA-16 18.165 15.616 38.438 0.85968 2.11605 Zalduegui Morena et al 2007 Santos Ossa 1496 Azuaga S BA-17 18.149 15.598 38.334 0.85944 2.11218 Zalduegui Morena et al 2007 Santos Ossa 1497 Azuaga S BA-18 18.167 15.608 38.385 0.85914 2.1129 Zalduegui Morena et al 2007 Santos Ossa 1498 Azuaga S BA-19 18.167 15.602 38.56 0.85881 2.12253 Zalduegui Morena et al 2007 Santos Ossa 1499 Azuaga S BA-20 18.204 15.608 38.41 0.85739 2.10998 Zalduegui Morena et al 2007
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Ossa Klein et al 1513 Cerro Muriano CO39 18.75073 15.62019 38.87358 0.83305 2.07317 Morena 2009 Casilla del Ossa Klein et al 1514 CO40 18.27266 15.61073 38.26239 0.8543 2.09389 Cobre Morena 2009 Ossa Klein et al 1515 Gran Mina CO114 18.16754 15.58193 38.22799 0.85768 2.10416 Morena 2009 Ossa Klein et al 1516 La Pastora CO25 18.71701 15.65642 38.63111 0.83647 2.06394 Morena 2009 Ossa Klein et al 1517 La Loba CO55 18.17192 15.60485 38.31083 0.85873 2.10826 Morena 2009 Ossa Klein et al 1518 Gibla SE 7 18.28432 15.61644 38.33908 0.85408 2.0968 Morena 2009 Dayton & Ossa- 861 18.212 15.589 38.174 0.85597 2.09609 Dayton Morena (1986) Santos 183 Santa Brígida Pedroches BRI 18.251 15.621 38.3308 0.8559 2.1002 Zalduegui et al 2004 Santos 184 El Soldado Pedroches SOL 18.24 15.6116 38.3241 0.8559 2.1011 Zalduegui et al 2004 Santos Morras de 185 Pedroches MOR-2 18.255 15.6153 38.3446 0.8554 2.1005 Zalduegui Cuzna et al 2004 Santos 186 Guadalupe Pedroches MOR 18.231 15.6094 38.3234 0.8562 2.1021 Zalduegui et al 2004
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Santos Norte 187 Pedroches GAL-36 18.297 15.633 38.3651 0.8544 2.0968 Zalduegui Torrecampo et al 2004 Santos 188 Membrillejos Pedroches GAL-33 18.442 15.6296 38.577 0.8475 2.0918 Zalduegui et al 2004 Santos 189 El Águila Pedroches GAL-34 18.452 15.6362 38.6034 0.8474 2.0921 Zalduegui et al 2004 Santos 190 San Caetano Pedroches GAL-32 18.464 15.6427 38.6452 0.8472 2.093 Zalduegui et al 2004 Santos 191 San Rafael Pedroches GAL-31 18.469 15.6359 38.6187 0.8466 2.091 Zalduegui et al 2004 Klein et al 1521 Solana Pedroches CO19 18.89518 15.64594 38.36404 0.82804 2.03036 2009 Klein et al 1522 Encinilla Pedroches CO22 18.67031 15.65303 38.7046 0.83838 2.07305 2009 Chap Klein et al 1523 Pedroches CO 4 18.26094 15.61563 38.37245 0.85514 2.10131 Barrenado 2009 Klein et al 1524 Cantos Blancos Pedroches CO 5 18.7059 15.65246 38.61712 0.83675 2.06443 2009 Klein et al 1525 Montilla Pedroches CO13 19.71266 15.71542 38.53983 0.79722 1.95509 2009 Klein et al 1526 Medioduro Pedroches CO14 19.10664 15.6717 38.57997 0.82022 2.01919 2009
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Klein et al 1527 Requeia Pedroches CO16 18.87606 15.65761 38.65142 0.8295 2.04763 2009 Klein et al 1528 Fontanar Pedroches CO17 18.4497 15.63289 38.51194 0.84732 2.08742 2009 Klein et al 1529 Torrubia Pedroches CO31 18.44192 15.64109 38.59885 0.84813 2.093 2009 Klein et al 1530 Zumajo Pedroches CO32b 18.44796 15.64329 38.61628 0.84797 2.09326 2009 Klein et al 1531 Quebradillas Pedroches CO34 18.56372 15.64757 38.67078 0.84291 2.08313 2009 Klein et al 1532 Quebradillas Pedroches CO34 18.58379 15.65056 38.68268 0.84219 2.08152 2009 Klein et al 1533 A Higueruela Pedroches CO38 18.53373 15.64346 38.56774 0.84404 2.08094 2009 Klein et al 1534 La Pililla Pedroches CO48 18.46524 15.63459 38.46971 0.84671 2.08337 2009 Klein et al 1535 Cort Peralbo Pedroches CO49 18.49089 15.63458 38.55806 0.84553 2.08525 2009 Klein et al 1536 D. Lavera Pedroches CO64 18.57234 15.64395 38.59191 0.84232 2.07788 2009 Klein et al 1537 Tabernero Pedroches CO92 18.45616 15.63541 38.56687 0.84716 2.08964 2009 Klein et al 1538 Romana Pedroches CO93 18.7241 15.61927 38.84482 0.83418 2.07458 2009 Klein et al 1539 Osi Pedroches CO94b 18.55484 15.6408 38.58835 0.84295 2.07968 2009 Klein et al 1540 Osi Pedroches CO94b 18.36207 15.61173 38.34769 0.85021 2.08841 2009
ID # Mine Region Identification 206/204 207/204 208/204 207/206 208/206 Reference
Klein et al 1541 Quiros Pedroches CO95 18.45234 15.63352 38.55485 0.84723 2.08942 2009 Klein et al 1542 Garabato Pedroches CO96a 18.49068 15.63533 38.59809 0.84558 2.08744 2009 Klein et al 1543 Garabato Pedroches CO96b 18.53777 15.63958 38.63741 0.84367 2.08424 2009 Klein et al 1544 Soberbio Pedroches CO97a 18.16586 15.5985 38.29099 0.85867 2.10786 2009 Klein et al 1545 Soberbio Pedroches CO97b 18.77077 15.64068 38.51938 0.83326 2.05208 2009 Klein et al 1546 Posadilla Pedroches CO107 18.52617 15.64326 38.68497 0.84439 2.08812 2009 Klein et al 1547 Cº Minillas Pedroches CO61 18.42124 15.6335 38.53152 0.84866 2.09168 2009 Klein et al 1548 Aº de la Virgen Pedroches CO28 18.48508 15.6442 38.64382 0.84633 2.09054 2009 Klein et al 1549 Almadenejos Pedroches CO77 19.22474 15.67989 39.0095 0.81582 2.0291 2009
Klein et al 1550 Aº Cuezo Pedroches CO78 19.2511 15.67989 39.00836 0.81449 2.02628 2009
Klein et al 1551 Escoriales Pedroches J 8 18.38619 15.63508 38.53145 0.85038 2.0957 2009 Klein et al 1552 S. Galiarda Pedroches J10 18.47242 15.63851 38.52577 0.84659 2.08554 2009