The Hourglass (Edited from Wikipedia)

SUMMARY

An hourglass (or sandglass, sand timer, sand watch, or sand clock) is a mechanical device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated trickle of material (historically sand) from the upper bulb to the lower one. Factors affecting the time interval measured include the sand quantity, the sand coarseness, the bulb size, and the neck width. Hourglasses may be reused indefinitely by inverting the bulbs once the upper bulb is empty.

HISTORY

Antiquity

The origin of the hourglass is unclear. Its predecessor the clepsydra, or water clock, may have been invented in ancient Egypt. According to the American Institute of New York, the clepsammia or sand-glass was invented at Alexandria about 150 BC. According to the Journal of the British Archaeological Association the so-called clepsammia were in use before the time of St. Jerome (335 AD), and the first representation of an hourglass is in a sarcophagus dated c. 350 AD, representing the wedding of Peleus and Thetis, discovered in Rome in the 18th century, and studied by Winckelmann in the 19th century, who remarked the hourglass held by Morpheus in his hands.

Reappearance in the Early Middle Ages

There are no records of the hourglass existing in Europe prior to the Early Middle Ages. In the 8th century it is mentioned by a monk named Luitprand, who served at the cathedral in Chartres, France. But it was not until the 14th century that the hourglass was seen commonly, the earliest firm evidence being a depiction in the 1338 fresco Allegory of Good Government by Ambrogio Lorenzetti.

Use of the marine sandglass has been recorded since the 14th century. The written records about it were mostly from logbooks of European ships. In the same period it appears in other records and lists of ships stores. The earliest recorded reference that can be said with certainty to refer to a marine sandglass dates from c. 1345, in a receipt

1 of Thomas de Stetesham, clerk of the King's ship La George, in the reign of Edward III of England.

Marine sandglasses were very popular on board ships, as they were the most dependable measurement of time while at sea. Unlike the clepsydra, the motion of the ship while sailing did not affect the hourglass. The fact that the hourglass also used granular materials instead of liquids gave it more accurate measurements, as the clepsydra was prone to get condensation inside it during temperature changes. Seamen found that the hourglass was able to help them determine longitude, distance east or west from a certain point, with reasonable accuracy.

The hourglass also found popularity on land. As the use of mechanical clocks to indicate the times of events like church services became more common, creating a "need to keep track of time", the demand for time-measuring devices increased. Hourglasses were essentially inexpensive, as they required no rare technology to make and their contents were not hard to come by, and as the manufacturing of these instruments became more common, their uses became more practical.

Hourglasses were commonly seen in use in churches, homes, and work places to measure sermons, cooking time, and time spent on breaks from labor. Because they were being used for more everyday tasks, the model of the hourglass began to shrink. The smaller models were more practical and very popular as they made timing more discreet.

After 1500, the hourglass was not as widespread as it had been. This was due to the development of the mechanical clock, which became more accurate, smaller and cheaper, and made keeping time easier. The hourglass, however, did not disappear entirely. Although they became relatively less useful as clock technology advanced, hourglasses remained desirable in their design. The oldest known surviving hourglass resides in the British Museum in London.

DESIGN, MATERIAL, AND USES

Little written evidence exists to explain why its external form is the shape that it is. The glass bulbs used, however, have changed in style and design over time. While the main designs have always been ampoule in shape, the bulbs were not always connected. The first hourglasses were two separate bulbs with a cord wrapped at their union that was then coated in wax to hold the piece together and let sand flow in between. It was not until 1760 that both bulbs were blown together to keep moisture out of the bulbs and regulate the pressure within the bulb that varied the flow.

2 While some hourglasses actually did use sand as the granular mixture to measure time, many did not use sand at all. The material used in most bulbs was a combination of "powdered marble, tin/lead oxides, and pulverized, burnt eggshell". Over time, different textures of granule matter were tested to see which gave the most constant flow within the bulbs. It was later discovered that for the perfect flow to be achieved the ratio of granule bead to the width of the bulb neck needed to be 1/12 or more but not greater than 1/2 the neck of the bulb.

Hourglasses were an early dependable, reusable and accurate measure of time. The rate of flow of the sand is independent of the depth in the upper reservoir, and the instrument will not freeze in cold weather.

From the 15th century onwards, they were being used in a range of applications at sea, in the church, in industry and in cookery.

During the voyage of Ferdinand Magellan around the globe, 18 hourglasses from Barcelona were in the ship's inventory, after the trip being authorized by emperor Charles V. It was the job of a ship's page to turn the hourglasses and thus provide the times for the ship's log. Noon was the reference time for navigation, which did not depend on the glass, as the sun would be at its zenith.

A number of sandglasses could be fixed in a common frame, each with a different operating time, e.g. as in a four-way Italian sandglass likely from the 17th century, in the collections of the Science Museum, in South Kensington, London, which could measure intervals of quarter, half, three-quarters, and one hour (and which were also used in churches, for priests and ministers to measure lengths of sermons).

Symbolic Use

Unlike most other methods of measuring time, the hourglass concretely represents the present as being between the past and the future, and this has made it an enduring symbol of time itself.

The hourglass, sometimes with the addition of metaphorical wings, is often depicted as a symbol that human existence is fleeting, and that the "sands of time" will run out for every human life. It was used thus on pirate flags, to strike fear into the hearts of the pirates' victims. In England, hourglasses were sometimes placed in coffins, and they have graced gravestones for centuries. The hourglass was also used in alchemy as a symbol for hour.

3 The former Metropolitan Borough of Greenwich in London used an hourglass on its coat of arms, symbolizing Greenwich's role as the origin of GMT. The district's successor, the Royal Borough of Greenwich, uses two hourglasses on its coat of arms.

WATER CLOCKS

A water clock or clepsydra is any timepiece in which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel where the amount is then measured.

Water clocks, along with sundials and hourglasses, are likely to be the oldest time- measuring instruments. Where and when they were first invented is not known, and given their great antiquity it may never be. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in Babylon and in Egypt around the 16th century BC. Other regions of the world, including India and China, also have early evidence of water clocks, but the earliest dates are less certain.

Some modern timepieces are called "water clocks" but work differently from the ancient ones. Their timekeeping is governed by a pendulum, but they use water for other purposes, such as providing the power needed to drive the clock by using a water wheel or something similar, or by having water in their displays.

The Greeks and Romans advanced water clock design to include the inflow clepsydra with an early feedback system, gearing, and escapement mechanism, which were connected to fanciful automata and resulted in improved accuracy. Further advances were made in Byzantium, Syria and Mesopotamia, where increasingly accurate water clocks incorporated complex segmental and epicyclic gearing, water wheels, and programmability, advances which eventually made their way to Europe. Independently, the Chinese developed their own advanced water clocks, incorporating gears, escapement mechanisms, and water wheels, passing their ideas on to Korea and Japan.

Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. These early water clocks were calibrated with a sundial. While never reaching a level of accuracy comparable to today's standards of timekeeping, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by more accurate pendulum clocks in 17th- century Europe.

A water clock, also known as a clepsydra, uses a flow of water to measure time. If viscosity is neglected, the physical principle required to study such clocks is the Torricelli's law. There are two types of water clocks: inflow and outflow. In an outflow

4 water clock, a container is filled with water, and the water is drained slowly and evenly out of the container. This container has markings that are used to show the passage of time. As the water leaves the container, an observer can see where the water is level with the lines and tell how much time has passed. An inflow water clock works in basically the same way, except instead of flowing out of the container, the water is filling up the marked container. As the container fills, the observer can see where the water meets the lines and tell how much time has passed.

MARINE SANDGLASS

A marine sandglass is a timepiece of simple design that is a relative of the common hourglass, a marine (nautical) instrument known since the 14th century (although reasonably presumed to be of very ancient use and origin). They were employed to measure the time at sea or on a given navigational course, in repeated measures of small time increments (e.g., 30 minutes). Used together with the chip log, smaller marine sandglasses were also used to measure the boat speed through the water in knots.

Although vital to maritime navigation, marine sandglasses were not accurate measuring instruments for the passage of time; many design and environmental factors could affect the duration of sand's flow, and therefore its reported time. Their use continued through the early 19th century, when they were supplanted by reliable mechanical timepieces, and by other advances in marine navigation.

Importance in Navigation

In long-distance navigation through the open ocean, the sandglass or "glass" used to measure the time was a tool as important as the compass (which indicated sailing direction, and so ship's course). Filled with the amount of sand suitable for measuring a lapse of half an hour, each time the sand emptied was also called a "glass"; eight glasses (four hours) defined a "watch". The times determined by the sandglass, along with the record in the logbook of the speed measured with the "chip log", permitted the ship's navigator to plot his map position. Multiplying the ship's speed by the time the course

5 had been kept (measured with the glass), gave traveled distance, a simple, overall method termed dead reckoning.

The marine sandglass was critical for maritime navigation before the 19th century. At the beginning of that century it became possible to navigate by the lunar distances. Prior to this, dead reckoning navigation based on sandglass-determined times was used, alongside determination of latitude using the quadrant (a kind of astrolabe ); this was the only system available to mariners to navigate the globe. The parallel use of relative time measurements at sea, and time measurement by mechanical clocks on land continued from at least 1350 to 1805, i.e., for more than 450 years.

Although vital to navigation, the marine glass was not an accurate instrument to measure the passage of time. The design of the glass affected its accuracy in time measurement; the uniformity in fineness of the sand, the inner diameter of the connecting tube, and design aspects allowing wear that would effect the flow of sand all could contribute. In addition, many shipboard factors could affect the duration of sand's flow and therefore influence the time measured, including the humidity inside the glass, the ability for it to be positioned in a perfectly vertical position, and the acceleration or deceleration of the ship's movements. Finally, the use of short duration glasses to measure long periods of time introduced further error. Marine glass use was supplanted by reliable mechanical timepieces, and by other advances in marine navigation.

THE RECONQUISTA

The Reconquista ("reconquest") is a period in the history of the Iberian Peninsula, spanning approximately 770 years, between the initial Umayyad conquest of Hispania in the 710s and the fall of the Emirate of Granada, the last Islamic state on the peninsula, to expanding Christian kingdoms in 1492. The Reconquista ended immediately before the European re-discovery of the Americas—the "New World"— which ushered in the era of the Portuguese and Spanish colonial empires.

After the Islamic Moorish conquest of nearly all of the Iberian Peninsula in 711–718 and the establishment of the emirate of Al-Andalus, an Umayyad expedition suffered a major defeat at the Battle of Toulouse and was halted for a while on its way north. Odo of Aquitaine had married his daughter to Uthman ibn Naissa, a rebel Berber and lord of Cerdanya (maybe of all current Catalonia too), in an attempt to secure his southern borders in order to fend off Charles Martel's attacks on the north. However, a major punitive expedition led by Abdul Rahman Al Ghafiqi, the latest emir of Al-Andalus, defeated and killed Uthman. The Muslim governor mustered an expedition north across

6 the western Pyrenees, looted areas up to Bordeaux, and defeated Odo in the Battle of the River Garonne in 732.

A desperate Odo turned to his archrival Charles Martel for help, who led the Frankish and leftover Aquitanian armies against the Umayyad armies and defeated them at the Battle of Tours in 732, killing Abdul Rahman Al Ghafiqi. Moorish rule began to recede, but it would remain in parts of the Iberian peninsula for another 760 years.

THE PERSISTENCE OF COLUMBUS

Christopher Columbus was an Italian explorer, navigator, colonizer, and citizen of the Republic of Genoa. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean. Those voyages, and his efforts to establish permanent settlements on the island of Hispaniola, initiated the European colonization of the New World.

Under the Mongol Empire's hegemony over Asia (the Pax Mongolica, or Mongol peace), Europeans had long enjoyed a safe land passage, the Silk Road, to the Indies (then construed roughly as all of south and east Asia) and China, which were sources of valuable goods such as spices and silk. With the fall of Constantinople to the Ottoman Turks in 1453, the land route to Asia became much more difficult and dangerous. Portuguese navigators tried to find a sea way to Asia.

In 1470, the Florentine astronomer Paolo dal Pozzo Toscanelli suggested to King Afonso V of Portugal that sailing west would be a quicker way to reach the Spice Islands, Cathay, and Cipangu than the route around Africa. Afonso rejected his proposal. Portuguese explorers, under the leadership of King John II, then developed a passage to Asia by sailing around Africa.

Major progress in this quest was achieved in 1488, when Bartolomeu Dias reached the Cape of Good Hope, in what is now South Africa. Meanwhile, in the 1480s, the Columbus brothers had picked up Toscanelli's suggestion and proposed a plan to reach the Indies by sailing west across the "Ocean Sea", i.e., the Atlantic. However, Dias's discovery had shifted the interests of Portuguese seafaring to the southeast passage, which complicated Columbus's proposals significantly.

Washington Irving's 1828 biography of Columbus popularized the hoax that Columbus had difficulty obtaining support for his plan because many Catholic theologians insisted that the Earth was flat. In fact, nearly all educated Westerners had understood, at least since the time of Aristotle, that the Earth is spherical. The sphericity of the Earth is also accounted for in the work of Ptolemy, on which medieval astronomy was largely based.

7 Christian writers whose works clearly reflect the conviction that the Earth is spherical include Saint Bede the Venerable in his Reckoning of Time, written around AD 723. In Columbus's time, the techniques of celestial navigation, which use the position of the sun and the stars in the sky, together with the understanding that the Earth is a sphere, had long been in use by astronomers and were beginning to be implemented by mariners.

Columbus learned of an estimate that a degree of latitude (or a degree of longitude along the equator) spanned 56 ⅔ miles, but did not realize that this was expressed in the Arabic mile rather than the shorter Roman mile with which he was familiar (1,480 m). He therefore estimated the circumference of the Earth to be about 30,200 km, whereas the correct value is 40,000 km (25,000 mi).

[Note: This would not be the last time someone made a mistake converting between unit systems. On September 23, 1999, the NASA Mars Climate Orbiter burned up in the Martian atmosphere, due to ground-based computer software which produced output in non-SI units of pound-seconds (lbf s) instead of the SI units of newton-seconds (N s) specified in the contract between NASA and Lockheed. That was a $327 million mistake. Fortunately for Columbus, his mistake didn't end so badly.]

Furthermore, because of other incorrect information about longitude at the time, Columbus estimated the distance from the Canary Islands to Japan to be about 3,000 Italian miles (3,700 km, or 2,300 statute miles). The true figure is now known to be vastly larger: about 20,000 km. No ship in the 15th century could have carried enough food and fresh water for such a long voyage, and the dangers involved in navigating through the uncharted ocean would have been formidable. Most European navigators reasonably concluded that a westward voyage from Europe to Asia was unfeasible. The Catholic Monarchs, however, having completed an expensive war in the Iberian Peninsula, were eager to obtain a competitive edge over other European countries in the quest for trade with the Indies. Columbus's project, though far-fetched, held the promise of such an advantage.

Though Columbus was wrong about the number of degrees of longitude that separated Europe from the Far East and about the distance that each degree represented, he did possess valuable knowledge about the trade winds, which would prove to be the key to his successful navigation of the Atlantic Ocean. He had an entrepreneurial edge and confidence in his abilities.

During his first voyage in 1492, the brisk trade winds from the east, commonly called "easterlies", propelled Columbus's fleet for five weeks, from the Canary Islands to The

8 Bahamas. The precise first land sighting and landing point was San Salvador Island. To return to Spain against this prevailing wind would have required several months of an arduous sailing technique, called beating, during which food and drinkable water would probably have been exhausted.

Instead, Columbus returned home by following the curving trade winds northeastward to the middle latitudes of the North Atlantic, where he was able to catch the "westerlies" that blow eastward to the coast of Western Europe. There, in turn, the winds curve southward towards the Iberian Peninsula.

In 1485, Columbus presented his plans to King John II of Portugal. The king rejected the offer because his experts thought Columbus’ distance estimate was too low.

In 1488, Columbus appealed to the court of Portugal once again and, once again, John II invited him to an audience. That meeting also proved unsuccessful, in part because not long afterwards Bartolomeu Dias returned to Portugal with news of his successful rounding of the southern tip of Africa (near the Cape of Good Hope). With an eastern sea route to Asia apparently at hand, King John was no longer interested in Columbus's far-fetched project.

Columbus traveled from Portugal to both Genoa and Venice, but he received encouragement from neither, nor from King Henry VII of England.

Success

Columbus had sought an audience from the monarchs Ferdinand II of Aragon and Isabella I of Castile, who had united several kingdoms in the Iberian Peninsula by marrying and were ruling together. On 1 May 1486, permission having been granted, Columbus presented his plans to Queen Isabella, who, in turn, referred it to a committee. After the passing of much time, the savants of Spain, like their counterparts in Portugal, replied that Columbus had grossly underestimated the distance to Asia. They pronounced the idea impractical and advised their Royal Highnesses to pass on the proposed venture.

However, to keep Columbus from taking his ideas elsewhere, and perhaps to keep their options open, the Catholic Monarchs gave him an annual allowance of 12,000 maravedis and, in 1489, furnished him with a letter ordering all cities and towns under their domain to provide him food and lodging at no cost.

After continually lobbying at the Spanish court and two years of negotiations, he finally had success in January 1492. Ferdinand and Isabella had just conquered Granada, the

9 last Muslim stronghold on the Iberian Peninsula, and they received Columbus in Córdoba, in the Alcázar castle. Isabella turned him down on the advice of her confessor. Columbus was leaving town by mule in despair when Ferdinand intervened. Isabella then sent a royal guard to fetch him, and Ferdinand later claimed credit for being "the principal cause why those islands were discovered".

In the April 1492 "Capitulations of Santa Fe", King Ferdinand and Queen Isabella promised Columbus that if he succeeded he would be given the rank of Admiral of the Ocean Sea and appointed Viceroy and Governor of all the new lands he could claim for Spain. He had the right to nominate three persons, from whom the sovereigns would choose one, for any office in the new lands. He would be entitled to 10 percent of all the revenues from the new lands in perpetuity. Additionally, he would also have the option of buying one-eighth interest in any commercial venture with the new lands and receive one-eighth of the profits.