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Great Plains Quarterly Great Plains Studies, Center for

1993

How Far West Am I?: The as An Explorer's Yardstick

Arlen J. Large The Wall Street Journal

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Large, Arlen J., "How Far West Am I?: The Almanac as An Explorer's Yardstick" (1993). Great Plains Quarterly. 752. https://digitalcommons.unl.edu/greatplainsquarterly/752

This Article is brought to you for free and open access by the Great Plains Studies, Center for at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Great Plains Quarterly by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. HOW FAR WEST AM I? THE ALMANAC AS AN EXPLORER'S YARDSTICK

ARLEN]. LARGE

On 14 1494, three ships from nearest tip of Europe. From that Columbus tried Spain lay anchored at the southeastern tip of to judge how far west he was at this stop on his Hispaniola. Their admiral, Christopher Co­ voyage to America. lumbus, looked up at a full expecting More than three hundred later something to happen, and it did. Meriwether Lewis made the same kind of cal­ Darkness nibbled at one edge of the lunar culation at his fort in modern North disc, the start of an predicted in an Dakota. His almanac forecast the in Green­ almanac carried by the Admiral. The book had wich, England, that a would end been prepared twenty years before by a on 14 1805. When the American ex­ mathematician called Regiomon­ plorer saw the moon escape from the same tanus. The almanac gave the and time of eclipse, he noted his North Dakota time and that eclipse as clocked from Europe. Watching figured his was 99°27' west of Green­ sand in an , Columbus decided his wich. local time for the lagged five and a half Both Columbus and Lewis investigated dis­ behind Portugal's Cape St. Vincent, the tant places at a time when was considered the main scientific way of fixing their positions. Historians of American explo­ ration know well the names of other travelers who were guided by the sky: Alexander Mackenzie, John Evans, David Thompson, Zebulon Pike, Stephen Long, John Charles Arlen]. Large is a former reporter for The Wall Street Fremont, and John Wesley Powell. Journal, 1956-86, and a president of the Lewis and Like Columbus and Lewis, these explorers Clark Trail Heritage Foundation. needed predicting the of various celestial events to help locate their place on . Their travel accounts, however, rarely [GPQ 13 ( 1993): 117-131] explained how almanacs contributed to their

117 118 GREAT PLAINS QUARTERLY, SPRING 1993 own of daily progress and to the Toledo, the Azores, Copenhagen, Paris, and maps they brought home. For example, many of others. The first English ran the mysterious columns of astronomical digits through the dome of St. Paul's Cathedral in filling the Lewis and Clark journals have mean­ before being switched to suburban ing only when linked to the almanacs they Greenwich. Not until 1884 did an interna­ carried. To understand how explorers navigated tional convention formally ratify Greenwich as America historians therefore might find it help­ the world's prime meridian, from which 180 ful to review the general concepts of antique degrees of longitude diverge east and west. 2 almanac usage. And that, in turn, requires an The idea of locating a place on Ptolomy's acquaintance with some European almanac sa­ coordinate grid by astronomy also had ancient vants-Giovanni Domenico Cassini, Tobias roots. Geographers quite early realized they Mayer, -whose names aren't could measure north-south travel by tracking often linked with the Great Plains and Rocky the elevation of the North at night or of the Mountains. at noon after adjusting for seasonal varia­ The kind of almanac used by navigators is tions. That gives latitude in degrees from the properly known as an , which forecasts equator; the earliest almanacs provided naviga­ the celestial positions of the sun, moon, and tors -round tables of the sun's seasonal planets. For a long while astronomy navigation height needed for this calculation. For the coexisted with the spookier practices of astrol­ harder task of measuring east-west movement, ogy; the Regiomontanus almanac, for one, Hipparchus of Nicaea theorized as early as 150 bragged that it could divine the and B.C.E. that a distant celestial occurrence like a predict the . The Paris Observatory lunar eclipse could be used to establish longi­ started compiling the first real astronomical tude. almanac in 1679, but it was the Royal Green­ The basic principle underlying the use of wich Observatory's Nautical Almanac and Astro­ astronomy to get longitude is that time equals nomical Ephemeris that became the prime posi­ distance: in one of time, the earth rotates tion-fixing handbook for the explorers and through 15° of longitude. That's the rate at mappers of North America's interior. which the of local noon moves west­ In calculating how far they had come from ward as the earth turns beneath the sun. Thus home, these investigators relied-as we still each hour of difference between the local noons rely-on conventions inherited from the an­ of two observers equals 15° of longitudinal sep­ cients: a global grid of north-south and east­ aration. The function of a celestial event that west coordinate lines developed by Claudius can be seen simultaneously in places distant Ptolomy in the second C.E. for the from each other is to signal the observer at Mediterranean world.! The arcing lines of each place the exact instant at which to mark Ptolomy's latitudes and chopped the the local time shown on each respective . arcing lines of his grid into 360 units or degrees, In practice an almanac substitutes for the home­ an inconvenient legacy of old Babylon. base observer, giving the traveling observer a Ptolomy decided degrees oflongitude should reference against which to compare local time. be counted eastward from a base meridian run­ The non-astronomical method of carrying a ning through the Canary Islands off the coast of chronometer set on the time of a known longi­ Morocco-to him the edge of the western world. tude serves the same function. Many mapmakers continued to count 360 de­ That's the theory, anyway. As will be seen, grees all the way around the globe from the precise position-fixing often was elusive in prac­ Canaries well into the eighteenth century, tice during the of exploration. A traveler which is why North American longitudes on could be misled by the built-in error of his own old maps often numbered in the high 200s. almanac if it placed the moon just a smidgeon Rival prime meridians proliferated, including away from its real location. Instruments still HOW FAR WEST AMI? 119 weren't terribly accurate, and paperwork mis­ earth casts a fuzzy-edged shadow on the moon, takes could snare busy seamen, soldiers, and and Lewis had to make a subjective decision traders who have had little practice in about timing the shadow's final departure. Be­ celestial mathematics. sides that, it would appear Lewis left out an Both Columbus in 1494 and Lewis in 1805 additional step in his calculations needed to put tried to exploit the theory with lunar , his local time on the same footing as the Green­ and their answers were both off the mark. Co­ wich time shown in his almanac. That addi­ lumbus faced greater disadvantages, for his tional adjustment alone would have brought hourglass was too crude for comparing his local him closer, but still thirty miles too far west of time with the eclipse time shown in Regio­ his true position.6 In drawing his map of the montanus's almanac. Also, his result depended area, co-commander William Clark decided to on accurate almanac predictions of the moon's borrow a better longitude derived from the work orbital motion, and Regiomontanus made his of a previous explorer, David Thompson. forecasts without benefit of the later writings of N icholas Cop~rnicus, Johannes Kepler, and Isaac For much of human the difficulty of Newton on how really work. finding longitude wasn't a terribly disabling If Columbus's local time of the eclipse was problem. Mediterranean sailors going east or five and a half hours behind his chosen base west needed only to keep the shore in sight. meridian of Cape St. Vincent, he would have Norsemen pushed their boats westward from been at about the same longitude as New Or­ Scandinavia to to Greenland in man­ leans-1500 miles too far west. Everybody has ageable stages by keeping Polaris steady off wondered how the great navigator could have their right shoulders. By around 1000 C.E. they been so wrong. Samuel Eliot Morison, the required only a final westward hop of about Admiral's best-known chronicler, has suggested three hundred miles across Davis Strait to bump Columbus gladly embraced the mistake because into "Helluland," today's Baffin Island. From it reinforced his conviction that he was on the there they turned south to their short-lived doorstep of Asia.3 Ernst Zinner, Regiomon­ L'Anse aux Meadows settlement in Newfound­ tanus's biographer, has offered a more specific land. Basically the route only required latitude explanation: in calculating sun hours from the navigation and, once learned, it was repeat­ western tip of Europe, Columbus overlooked able.7 the fact that Regiomontanus had given the The need to find longitude became more time of the eclipse for the meridian of Nurem­ pressing when advances in sailing technology berg in central Germany-not from Cape St. permitted long voyages across blue water, as Vincent in Portugal4• If you measure five and a dramatized by the difficulty Columbus had in half hours west from Nuremberg at a rate of 15° determining his position. The longitude puzzle per hour, in Columbus's latitude you land in the may actually have cost the life of Robert middle of the island of Hispaniola, only 200 Cavelier de LaSalle. From his base in Canada miles west of Columbus's anchorage. That's not this French entrepreneur led a small party south­ so bad, considering the handicaps. ward down the Mississippi River, reaching its Working with the 1805 eclipse, Lewis had mouth at the Gulf of Mexico on 9 1682. the advantages of an expensive chronometer to With an astrolabe-the ancestor of a modem record his local time plus the British Nautical sextant-LaSalle measured the altitude of Po­ Almanac's improved lunar positions based on laris and computed a latitude of 2 7° north of the Newton's laws of motion. His Fort Mandan equator.8 That was too far south by 130 miles, longitude computation of 99° 27' west of but something. He had at hand no better way Greenwich was eighty-five miles too far east of of figuring his longitude than did Columbus the modem figure of 101 °16'.5 Longitudes ob­ 188 years before, and for LaSalle there was no tained this way are inherently imprecise. The timely lunar eclipse. 120 GREAT PLAINS QUARTERLY, SPRING 1993

the longitude of the Mississippi's multiple mouths.lO Had LaSalle known that was the meridian reached on his 1682 visit by land, he could have ordered his ships north right there and nailed his target. Instead, he kept sailing west until he hit the coast of Texas. There the original mission fell apart, and LaSalle later was murdered by some of his own men. Ironically, it was just at this moment that European astronomers were devising the first real breakthrough in the longitude problem, one that would be of practical benefit to several explorers of the American land. Halley's com­ pass variation charts never became practical, partly because the magnetic pole itself kept wandering. Eclipses of the moon weren't helpful because on average there are only two of them each year-some years there are none at all­ not good enough for an explorer needing to know his longitude right now.ll But the solar system has other , and four of them were first seen circling the planet by the Paduan astronomer Galileo Gali­ FIG. 1. Giovanni Domenico Cassini, the Paris Observatory developer of longitude-finding with eclipses lei in 1610. Jupiter is an easy-to-find headlight of the moons of Jupiter. Courtesy of the Library of in the night sky, but its moons couldn't be seen Congress. without the small homemade telescope that Galileo turned upon it. Galileo quickly realized that an eclipse of a moon behind the planet could be clocked simultaneously by observers at Not knowing that longitude severely handi­ two places on earth, thus giving their relative capped LaSalle when he tried two years later longitude. In 1616 he offered his plan to the to return to the Mississippi's mouth by sea. King of Spain and again in 1636 to the seafarers LaSalle's convoy of would-be settlers pushed ofHolland.12 Because a navigator would have to into the Gulf of Mexico in 1684. En hold a long telescope steady on Jupiter, the route the ships' navigators readily computed method wouldn't work on a rolling ship at sea, latitudes and even took a stab at longitudes, so the Spanish and Dutch navies weren't inter­ possibly by measuring the local compass varia­ ested. tion. It had long been known that the mag­ After Galileo's death in 1642, however, his netic north pole is offset from the geographic idea was grabbed eagerly for use on dry land by pole and that a traveler's magnetic compass the brilliant team of scientists that Louis XIV would show a changing angle of offset as it was assembled at the Paris Observatory. Louis's prize moved east or west. Among others, England's catch was Giovanni Domenico Cassini (Fig. 1), Edmond Halley-later of comet fame-offered an Italian astronomer who spent sixteen years the shaky hope that contour maps linking refining Galileo's tables of the Jovian satellites these angles could be used to track 10ngitude.9 now known as 10, Europa, Ganymede, and Cal­ The method generally was inaccurate, but if listo. In 1690 the Observatory's national alma­ that's what LaSalle's ships were using, a reading nac, Connoissance des Temps, began publishing on 20 December rather correctly put them on regular predictions of the every-other- HOW FAR WEST AM l? 121

eclipses of 10 as timed from the meridian of midnight. Equivalent in Greenwich Paris. 13 would have been after dawn at 5:36 a.m. on The importance of Jupiter in cracking the 23. It didn't matter that a Greenwich observer longitude problem tends to be unappreciated couldn't actually see Jupiter in daylight; the today because the idea sounds so quaint. From calculated almanac time was what counted. Paris Cassini dispatched surveying teams to Earlier that day Mackenzie had used sextant aim telescopes at Jupiter from Siam, Egypt, sightings of the sun's altitude to synchronize Madagascar, Goa, and the Caribbean islands of his with local noon. He used that watch Guadeloupe and Martinique. Cassini thus es­ to time Ganymede when it actually appeared, tablished the first good global network of and 45 later he similarly timed an benchmark longitudes from which other longi­ emersion of 10, the first satellite. The Scottish tudes could be estimated. The moment a distant explorer subtracted each of these observed times surveyor saw 10 disappear behind Jupiter or its trailing shadow cast by the sun, he knew ex­ actly what time it was in Paris by referring to the French almariac. Comparing Paris time with his local time of lo's disappearance gave longi­ 1 U L~Y (15) tude at the familiar rate of 15° for each hour of Itt. 1293·' Houriy difference. :11 Semilii. Timedi'D" Loptittlin Plate or. .t'" 1'3 meter of of the SuD'• M~·t. Eclipse tables for all four Galilean satellites &bcSwa. . ~~. ~~- DiftarMJe. Node.· were adapted for the meridian of Greenwich If M •. S, M.S. !l.D; ),t.. when Britain's Royal Observatory began issuing ~;~~. ... ., ~ - ." its Nautical Almanac there in 1766. The alma­ . i -IS- ~'9 . I. 8,6 t. I~,C ·0.99#51 J: '.19 nac declared that eclipses of Jupiter's moons ? 1;•• ,.0 1. 8.J t. tail! 0. 6!>1io! f~ .. ~ I~ If; f7,' I. 8,0 ::'a;_ o;C!b,680 J•. B, at "are well known to afford the readiest, and for 19 l.Zlil 0.006869 ~; .. ii" IS· tii. I.~.. ~:f!.,. o. oMe07 1;.3 general Practice the best Method of settling the Ie wi. il I. ali!! r· Longitudes of Places at Land; and it is by their Means principally that Geography has been so ~Lip:'.i'.t a.'.ay.4.:n •• ~ JU.ti'£JL much reformed within a Century past ...".14 .. .. Experts advised using a refracting telescope .it Satellite>. : ntl Sateliiti• big enough to magnify Jupiter forty times for ,'. rEm~.. ,£mer/iOn...... ' .. " accurate timing of the moons as they disap­ ~ H.M; •. ii.y~ .": ~-:;;- ~!. H.M.S. .. , peared behind the planet (immersion) or pop­ I '1I.,a:. ,.: 9· 24; 27, ,I "51'------'J ir;' ',- ped into view (emersion). A London-bought . '7, 7· II ••, ea. 41. 19 J . s . J;~S. _,. 'u· u.'S8.1~ 8 ;:~s: sf~·, telescope lugged by Alexander Mackenzie to 1. 'ao..... 'f" . -Llf· is '.a . t- 31· 3'1'" Canada's Pacific coast in 1793 was awkward ~' .I.,J2. J. 'If' ,1+ .':.1 ~S u·,t zoJ · 10 ,. ." a It ,. so. 7 I; 13·3 4jJ;- .., .... .iL.fl. ,_. baggage for his ten-man party, but the effort u ~2q.H IS 1 al. fB. ,0 '.,'.4 paid off. On the night of 22 July Mackenzie set t,: i, . '1$' .'. 16.2'.. 4l :29 ~~'31' jo. Sf; ! 1!..Jl:. . it up near the now-famous rock at the saltwater a ;. ,-9'. 11.,6.:: ",l19 7 ;s·z+ . , Dean Channel where he inscribed the news of :...t. cz ••G 'W, Saiellite.CliIj. .- .Z.,..!!: his reaching the coast. An hour after , he rar.-· , ... ~". 'D ~o trained the telescope at the spot where his ::. 7· Jt). f ...·13 '16. 13':1 21 t'4;' s. II 22;3. tr· . Nautical Almanac said Ganymede, the third .ao. 16 ••~ 3C1 S'49 s..p. 129 .. satellite, would emerge from the planet's Ii 14...~la ~. shadow at 17 hours, 36 minutes, and 20 FIG. 2. British Nautical Almanac page showing eclipse (see Fig. 2). That was now-obsolete Greenwich times of Jupiter's moons, used by Alexander Mackenzie astronomical time, in which the day was reck­ in computing his 22 July 1793, Pacific coast longitude. oned from noon to noon instead of midnight to Courtesy of the Library of Congress. 122 GREAT PLAINS QUARTERLY, SPRING 1993

ant Zebulon Pike in 1806 when he was sent by General James Wilkinson on a spying mission to the Rocky Mountains. The general had in­ structed Pike

to employ your telescope in observing the eclipses of Jupiter's satellites, having previ­ ously regulated and adjusted your watch by your quadrant, taking care to note with great nicety the periods of immersions and emersions of the eclipsed satellites.

The actual longitudes would have to be com­ puted after Pike's return, however, because Wilkinson couldn't provide him with tables listing Greenwich times of the Jovian eclipses. The navigation plan was ruined when Span­ ish troops captured Pike in the Rockies and confiscated most of his papers, including the local times of the satellite eclipses he had ob­ served and recorded. When he got back to FIG. 3. Nevil Maskelyne, Royal Greenwich Observa­ Washington, Pike at last had access to an tory editor of the Nautical Almanac and Astronom­ almanac's Greenwich times, but now there were ical Ephemeris from 1766 to 1811. The Van der Puyl no observed western eclipse times to compare portrait at the Royal Society, courtesy of the Library them with, and thus no longitudes. That made of Congress. the map of his trip "very imperfect," he con­ ceded. 16 With both telescope and almanac at hand, from the predicted almanac times of the Lieutenant John Charles Fremont readily ob­ emersions, and averaged the differences. This tained longitudes from fourteen Jupiter obser­ average lagged 8 hours, 32 minutes, and 2 vations during his 1843-44 tour of the west. Like seconds behind Greenwich time, from which other explorers, weary after a hard day's travel, he computed a longitude of 128°02' W. Fremont experienced the tedium of waiting into That was thirty-five miles too far west of the the night for an almanac-predicted event in the longitude given on modern maps, but Mackenzie heavens. Reporting from Idaho, he said, "I sat up was relieved to get anything. "I had now deter­ for an observation of the first satellite of}upiter, mined my situation," he said in his published the emersion of which took place about mid­ journal, "which is the most fortunate circum­ night; but fell asleep at the telescope." When he stance of my long, painful, and perilous journey, woke up 10 was already there, too late to time. 17 as a few cloudy days would have prevented me In Oregon Charles Preuss, the German drafts­ from ascertaining the final longitude of it. "IS man of Fremont's highly regarded maps, For much of the next century Jupiter's moons grumbled into his diary about a campfire vigil offered other explorers of America an on-the­ for an eclipse of 10: "To tell the truth, I wish the spot way to figure longitude without a lot of dear Lord had not attached any satellites at all tough mathematics, provided they carried tables to Jupiter. One can lose one's mind over it. of eclipse predictions. Not having them was These immersions occur so often that one for­ only one of the misfortunes that befell Lieuten- gets how to sleep."ls HOW FAR WEST AM I? 123

Other explorers didn't want to bother with a A traceable thread of Maskelyne's influence fragile telescope, fearing it would be too easily on North American exploration can be seen in broken on a long trip. For them the main the career of an early "computer" he trained to alternative for getting longitude was a method figure the tedious tables of moon-star angles in known as "lunar distances," which required only the almanac. The computer, named William a sturdy sextant for measuring angles in the sky. Wales, left his Greenwich job in 1772 to sail on The concept had been experimented with by Captain James Cook's second exploratory voy­ European theorists for a couple of . It age to the Pacific.21 During that trip Wales only came into practical use for travelers a trained a teenage midshipman named George before the American Revolution, thanks Vancouver in the mathematical intricacies of mainly to Nevil Maskelyne (Fig. 3), the fifth obtaining longitude by lunar distance.22 T wen­ Astronomer Royal at the Greenwich Observa­ ty years later Vancouver commanded his own tory. naval survey of America's Pacific Northwest Maritime Britain wanted above all a way to coast, using Greenwich-time chronometers and find longitude at sea, which Jupiter couldn't Maskelyne's lunar distances to fix longitudes for provide. Since·its founding in 1675 the Green­ the mouth of the Columbia River and other wich Observatory had been compiling a catalog notable points. 23 Vancouver's longitudes be­ of accurate positions of to serve as a refer­ came the accepted western anchors for maps ence background for the moving moon. In 1755 drawn by William Clark and later explorers of the British were able to borrow a superior table the interior. of lunar motions carefully worked out by a P. Elmsly, a bookseller in the Strand, was German astronomer, Tobias Mayer. 19 the authorized London outlet for the Nautical Maskelyne used all this material to assemble Almanac. From there copies easily found their tables predicting where the moon would be at way to America, where they were considered three-hour intervals, Greenwich time, every fair game for pirating by anybody with a print­ day of the year. The locations were shown as ing press. In 1802 John Garnett, a publisher in angular distances between the moon and a New Brunswick, New Jersey, began printing nearby star or the sun. The angles were con­ what he described as "a cheap American Edi­ stantly changing as the moon moved eastward tion of the Nautical Almanac beginning with by roughly its own diameter each hour against 1803 to be continued regularly, and no pains the starry background. When a distant naviga­ will be spared to make it equally correct with tor determined that the moon and one of the the original." Needing in 1804 a new "London" reference stars were at exactly the angular dis­ edition for copying, the publisher obtained one tance shown in the almanac, he knew the time from the American Philosophical Society in in Greenwich. Philadelphia. Said a grateful Garnett: "I am The Greenwich Observatory's annual Nauti­ much obliged to you for sending the N.A. of cal Almanac and Astronomical Ephemeris first 1807, which shall now be printed without de­ appeared in 1766 with Maskelyne's lunar dis­ lay."24 tance tables as its centerpiece. The former From whatever source, the British lunar dis­ clergyman was to continue editing the almanac tance tables were circulating even before the until his death in 1811. Even he conceded that turn of the century in America for use by land a single moon-star distance measurement could explorers. In the 1790s both James Mackay and incur an error of nearly a degree of longitude, John Evans used lunar distances in mapping due partly to the residual "imperfection" of the stretches of the Missouri River for their Span­ almanac's lunar tables. For greater accuracy he ish-licensed trading company, which had more advised the traveler to measure the moon's than an academic interest in finding longitude. distance from two stars, "ifhe can be so lucky."20 In those days the longitude of the entrance of 124 GREAT PLAINS QUARTERLY, SPRING 1993

TABLE 1.

ASTRONOMICAL OBSERVATIONS FOR NAVIGATION RECORDED DURING THE LEWIS AND CLARK EXPEDITION From 17 December 1803, at Camp Dubois, Illinois, to 25 1806, at Cheyenne River, South Dakota

Number of Observations I

For Latitude (40%) Sun's altitude at noon 104 Sun's altitude, a.m. or p.m. 8 Altitude of Polaris 1

For Longitude (49%) To obtain Greenwich time Lunar distance from sun 32 Lunar distance from Nautical Almanac stars 28 Lunar eclipse 1 To obtain local time Sun's equal altitudes in a.m. and p.m., to determine the moment of local noon. Completed observations, with at least one p.m. reading2 66 Incomplete due to clouds 11

For Variation of Magnetic Compass from True North (11 %) Sun's azimuth and altitude, a.m. or p.m. 25 Azimuth of Polaris 5

Total Recorded Observations 281

IAn "observation" consists of one or more taken for a single objective. For example, six successive readings of the angle between the moon and Spica are counted as a single observation, as is one measurement of the azimuth of Polaris from true north.

2Also used to produce 2 latitude estimates.

Source: Journals of the Lewis and Clark Expedition, edited by Gary Moulton (Lincoln: University of Nebraska Press, 1983-) and Reuben Gold Thwaites, OriginalJournals of the Lewis and Clark Expedition (New York: Dodd, Mead, 1904-05). HOW FAR WEST AM I? 125 the Platte River into the Missouri was a demar­ can points as Boston, New Orleans, San Fran­ cation line for carving up markets in the Indian cisco, Mexico City, and Nootka Sound. trade.2s Lewis and Clark at no point during their trip In December 1797, David Thompson, sur­ specifically mentioned consulting the Nautical veyor for the North West Company of fur Almanac, but its distinctive signature runs traders, arrived at the Mandan villages in North throughout the pages of their journals. Maske­ Dakota from his base in Manitoba. He brought lyne listed just nine stars as nighttime reference only a sextant for matching moon-star angles points for lunar positions: , Alpha with those in Maskelyne's almanac. The thor­ Aquilae, Antares, Fomalhaut, Alpha Arietis, oughly professional Thompson computed a lon­ Alpha Pegasi, Pollux, Regulus, and Spica.3l gitude of 101°14' west of Greenwich for this Those nine stars-and only those nine-are the important tribal trade mart and drew a sketch ones recurring throughout the expedition's map of the area. 26 In 1803 Meriwether Lewis records of observed angular distance from the picked up a copy of Thompson's map from the moon. British Embassy in Washington, and the Mandan Lunar distance purists decreed it wasn't longitude became another major benchmark for enough for a navigator to measure the "appar­ his planned expedition west. 27 ent" moon-star angle alone. He also was re­ The bulky documentation of the Lewis and quired simultaneously to measure from the ho­ Clark expedition of 1803-06 offers a detailed rizon the altitudes of both the moon and target picture of land explorers struggling bravely star, to be used in dense calculations correcting with the demands of astronomical navigation. distortions caused by (See Table 1.) Unlike Thompson, Lewis and and the skyward sight-lines of his global loca­ Clark were Army men without much working tion (parallax). This formidable step, known as knowledge of the sky. The expedition's pre­ "clearing" the lunar distance, enriched some departure navigation coaches were Andrew British mathematicians who sold allegedly Ellicott, a Lancaster, Pennsylvania, astrono­ simple formulas for coping with it. 32 mer-surveyor, and Robert Patterson, mathemat­ Because of various shortcut formulas, text­ ics professor in Philadelphia. In 1803, at book descriptions of lunar-distance navigation an early point in the planning, Ellicott said don't explain how American explorers actually Lewis needn't try to compute longitudes from used the method in the field. When Major his lunar distance records until the trip's end Stephen Long journeyed to the Rockies in 1820, "because the transportation of the books, and he merely took apparent lunar distance angles tables, necessary for that purpose, would be (at just five locations on the whole round trip) found inconvenient on such a journey."28 Evi­ and ignored the "clearing" altitudes. Lieutenant dently somebody later decided the inconve­ ]. D. Graham, who later computed longitudes nience could be tolerated, as Lewis left for the from these records, said a shortcut formula made west with all the manuals needed to produce it good enough merely to know the time and longitudes in the field. These included Nautical latitudes at which the sextant readings were Almanacs for 1803, 1804, and 1805, a book on taken.33 Similarly, those entries of moon-star calculating lunar distances, and Maskelyne's and moon-sun angles in the Lewis and Clark own "Tables Requisite" for using the Nautical journals can't be understood if the reader also Almanac. 29 This last contained several crutches looks for "clearing" altitudes, because they aren't for laymen, such as handy table converting units there. Liberation from this chore was authorized of time into degrees of longitude.30 And for by Professor Patterson himself, who gave Lewis navigators who preferred to peek in the back of a set of navigational crib sheets with a shortcut the book, Maskelyne offered twenty-four pages formula to be used at those times, "as it may of known latitudes and longitudes for places frequently happen," when altitudes couldn't be around the world, including such North Ameri- taken.34 126 GREAT PLAINS QUARTERLY, SPRING 1993

FIG. 4. Meriwether Lewis's 9 1805, measurement of the moon's distance from Spica , to be matched with the Nautical Almanac's Greenwich time of the same separation . Courtesy of the American Philosophical Society, Philadelphia.

While Lewis left with a complete kit for had been known for years, was to be the only figuring his longitudes on the spot, President lunar distance calculation Lewis claimed to Jefferson told him to save his raw observations have made during the entire expedition. for delivery to the W ar Department, where There was at least one other attempt, how­ experts "concurrently" could run computations ever. At Fort Mandan on 23 1805, to check his results.35 At his jumpoff point near Lewis took a set of moon-sun angles, pegged his St. Louis, Lewis reported that he had fixed that chronometer to local noon, and began trying to camp's longitude with a complete lunar dis­ compute the corresponding time in Greenwich. tance calculation from seven sets of moon He reached the point for applying shortcut angles with the sun, Aldebaran, and Spica. In formulas to the "clearing" problem and, though the documents that have survived, however, he there was more room on the paper, quit in gave only the final answer-89°57'45" W­ apparent defeat.37 The captain evidently was without recording raw data that could be trying to see if a lunar distance longitude would checked by others.36 This unconfirmable re­ square with his result from the lunar eclipse the sult, made near a town where the longitude before. HOW FAR WEST AM l? 127

Except for this failed attempt, Lewis and nearly 36° west of the moon-the exact average Clark merely noted down the raw moon-star or was 35°56'43"-at 11 hours, 37 minutes, and 20 moon-sun angles for longitude calculation by seconds in the evening, the average of Lewis's others upon their return home. How this should chronometer times. have worked in tandem with the Nautical Al­ The Nautical Almanac (see Fig. 5) shows manac is illustrated by Lewis's lunar distance that on 9 June Spica would be nearly 36° west of observation on the evening of 9 June 1805, at the moon at 1800 hours, Greenwich astronomi­ the junction of the Missouri and Marias Rivers cal time-the exact angle being 35°59'24". The in modern Montana. (See Fig. 4.) The captain task for a mathematician back in Washington took six sextant sightings of the distance be­ would be to find the exact Greenwich time of tween the moon's western edge and the bright Lewis's recorded moon-Spica angle. For that he star Spica. The moon's eastward motion away would have to work a series of corrections on from the star is discernable in the slight widen­ the raw observations of both time and dis­ ing of their angular separation, but motion tance. These would involve Lewis's own 9 June wasn't the operative factor. Rather, the six calculation relating his chronometer to local entries would be averaged into single values of noon at the Marias, plus a "clearing" correc­ time and distance for the purpose of washing out tion for Lewis's latitude, plus a final interpola­ any small eyeball misjudgments at the sextant. tion of the moon's motion to fit it within the This would freeze into the record the observa­ almanac's three-hour Greenwich time inter­ tion that on 9 June at the Marias, Spica was vals. If everything worked right, the computed

~ o i DISTANCES of MOON's Center from SUN, and from STARS WEST of her .

.xXlh. Scars NODIt. ITlh. VIh. IX'. II MiJlti~~Vh. XVII1h. Oay. ------Names. O.M.S. 'O.M.S. O.M.S. O.M.S·. I D. M. S. O. M. S. O. M. S. O.M. S -'----- I 53, z401 9 ~:;. 5.10 t'45'37 7-115.41 60. S,.1I3 ~44'41 63'::3'36 ~:s II - 60'40017 Sol8. 2 9· 5).24 71'32.23 73' 8'58 74·45.10 70oll0'59 77'56. 25 90.2b.l0 The Sun. 3 79'3,·117 81. b. b 82'4°.112 84.14.16 85' 47' 48187' 110. 57 88. 53' 44 4 9"58"4 93. 119.58 95· 1·2Z 96 •.~z. 25 98. 3' 9 99· 33' 32101. 3' 37 102'33. 23 5 104; 2. 50 '05' 3 1• 59 10i" o. 5' 108.a9' ZO 109' 57' 43;111. 25' 44 112. 53' 3 1 114.21, 1 __-- __b_!..:.5.: ~8~ :.2:..!.5· 16 118. 411..:.,! Ilia. 8'34 111/'34'52 -_.- 4 18. 48. 57 20. a6. ,5 u· 3' 3 ' 113. 39:s3 ~6. 35 2b. 53-7 -28. 119: 117 30' 5' 35 5 3' ~ 4 I. 3 I 33' 17· 12 34' 52. 39 36.117'511 38.11'52 39'37'3741. 12. 8 42.46. 20 Regulus. 49' 1.24 5°'34'31 7'37 53'4°. 116 55· 13' 3 6 44· 20. 30 4~' $4' 21 47' 27' 59 lil. J-C 61.SI'42 611'53.26 4.25' a 65'5b.1I5 67. 27'41 7 56'4~olI9 5 01 7.43 59'49'48 00 8 68. 5 . 48 70 • s9· 4b 7'" 0. 37 ..D..:.l!:.!2..--ll:.. I. 5.3 - o 21. ----- 8 - - - ,- 4· II I""'" ,,' ~ ------2:&'33'~1 ·41 9 27' 11'37 .s. 311. III JP' 1'44 31'3[.14 33' 0'4[ 34' 3°' 35' 59. 114 If,.2 3~' ~ . Spica '!r 10 38'51'55 41'S6.1~ 43'.5 ••0 H·S4·s3 46• 23. 2 ~9·u.15 -40 ••" 6 2 61011.29 II 50. S0. 7 ~'01 • 57 3' 41' 4 &5 016• 33 t'45. 19 58• 14' 3 59'4 '41 IS b •• 40. Ie .. a·So t5' 31' 30 7' 6. 9 8. 34' 48 : . I .~ ,

FIG. 5. Top half of the Nautical Almanac for June 1805, with the circled moon-Spica distance corresponding to Lewis's measurement at the Marias. Courtesy of the Library of Congress. 128 GREAT PLAINS QUARTERLY, SPRING 1993 time difference between the Marias and Green­ tude for Cape Disappointment in the west. wich would be 7 hours and 22 minutes, or a Laborious lunar distance readings had been correct modem longitude of 110°29' W. taken at what Lewis and Clark considered key The English chronometer obtained by Lewis intermediate points: the Great Falls and Three in Philadelphia wasn't reliable over extended Forks of the Missouri, the east and west shoul­ periods. It therefore wasn't generally used in the ders of the Rockies, and the junction of the manner intended for sea captains-keeping it Snake and Columbia Rivers. These raw num­ set on Greenwich (or other base meridian) time bers simply moldered without anyone convert­ for comparison with the traveler's local time.38 ing them to longitudes to be fitted to Clark's Rather, the explorers employed the instrument map. as an ordinary watch for connecting the mean The un interpreted readings forced Clark to times of a short- series of astronomical guess at the longitudes crossed by the expedition sightings. between the three known anchors. He did it by Lewis and Clark's decision to forego lunar simple dead reckoning, adding up the estimated distance longitude calculations until their re­ distance covered on each leg of each compass turn made careful recording of their field obser­ heading. And that, in tum, distorted the single vations all the more important, but, sadly, their most important geographical discovery brought bookkeeping was often sloppy. Near Beaverhead home by Lewis and Clark: the surprising width of Rock in Montana, Clark measured the distance the Rocky Mountain chain. Because of dead between and the moon and Antares and later reckoning errors Clark's map somewhat exag­ gave the readings to Lewis; as recopied by Lewis, gerated this valuable discovery, making the the recorded observation showed the moon Rockies even wider than they are. On his 1814 going backwardsp9 map nearly 6° of longitude separate the expe­ If the astronomy notes approached short­ dition's eastern entrance at the Gates of the hand, it may have reflected the captains' as­ Mountains in Montana and its western exit sumption that they personally could clarify from the Bitterroots in Idaho. Just under 4° doubtful entries to mathematicians working on separate the same points on modem maps. Even the longitudes back in Washington. That this after Clark's map was published Jefferson still didn't happened was part of the whole deplor­ kept hoping-in vain-that the government able post-expedition collapse of the manage­ would hire mathematicians to "correct the lon­ ment of the Lewis and Clark records. The blame gitudes" and thus establish "the correct geogra­ must fall partly on Jefferson for giving both phy of the country, which was the main object Lewis and Clark cushy patronage jobs in distant of the expedition."41 St. Louis instead of ordering them immediately During later explorations of the nineteenth to work full time on publication of their maps century, Thompson-type professionals contin­ and journals. Four years after expedition's re­ ued to get good longitudes while Lewis-and­ turn, a cold partial record of observations was Clark amateurs didn't. The War Department's mailed to mathematician Ferdinand Rudolph multi-pronged 1854 search for a railroad route Hassler in upstate New York. Without anyone to the Pacific produced striking contrasts of to explain the shorthand, he couldn't decipher performance. Captain John Pope, an Army it.40 topographical engineer, used lunar distances to As a result, Clark's map of the expedition's establish the longitudes of seven main reference whole route finally published in 1814 was an­ points on a far-southern rail route across Texas. chored by just three good longitudinal points, At twenty-five-mile intervals between these all borrowed from others: the well-known posi­ points he noted time differences on this chro­ tion of St. Louis in the east, Thompson's ap­ nometer to estimate longitudes for twenty inter­ proximate longitude for Fort Mandan in the mediate places. This chain of measurements middle, and Vancouver's approximate longi- fixed the Texas route "with some considerable HOW FAR WEST AM I? 129 degree of accuracy," boasted PopeY Much dif­ broadcasts of time signals by radio, and Euro­ ferent were the results of a northern survey near pean governments quickly followed. That gave the Canadian border led by Isaac Stevens, a radio-equipped navigators a foolproof way of newly appointed governor of Washington Ter­ knowing Greenwich time, and it soon ended ritory. Stevens had to confess his survey's longi­ any need for the eye-straining lunar distance tudes "are not good." He offered abundant ex­ tables pioneered by Maskelyne. The British cuses: the chronometers went haywire, and Nautical Almanac finally stopped publishing nobody in his party knew how to work lunar them in 1907.46 distances. Like Clark, he had to fall back on The founding of national observatories in dead reckoning estimates of distance traveled.43 Europe---driven by the needs of navigators­ When John Wesley Powell made his first trip provided an astronomical basis for comparing through the Colorado River's Utah and Arizona time differences across global distance. Proce­ canyons in 1869 he got his longitudes in a dures of rough accuracy thus were available for routine professional way with lunar distances.44 attempts at scientific position-fixing in North But Powell was able to use a new technological America during the eighteenth and nineteenth wrinkle freeing him from almanac time com­ centuries, and they helped produce increasingly parisons when he started a complete survey of refined maps of the interior as more explorers the Grand Canyon itself in 1871. The U.S. learned how to use them. Though almanacs still Coast Survey previously had nailed down the have a fall-back role, longitude-finding in the longitude of Salt Lake City as 111°53' west of twentieth century grew away from astronomy Greenwich. Powell's wilderness surveyors with the advent of radio time signals. Today, marked the instant when the earth's rotation even the hallowed comparison of time differ­ carried a target star across their overhead merid­ ences between two places is becoming obsolete. ian. They immediately exchanged time signals Anyone with the price of a compact black box over a telegraph line with observers in Salt Lake can get instant digital readouts of latitudes and City watching for the same event. The slight longitudes signaled from manmade satellites time difference gave Powell's longitude from orbiting eleven thousand miles overhead. Nevil Salt Lake City, and thus by extension from Maskelyne would be amazed. Greenwich. It took Almon Harris Thompson, Powell's topographer, more than a in 1872 to get NOTES his instruments and telegraph table set up in the little town of Kanab, Utah, a major survey 1. See John Parker, Discovery: Developing Views reference point fifty miles from the north rim of of the Earth from Ancient Times to the Voyages of Captain Cook (New York: Chas. Scribner's Sons, the Grand Canyon. New technology could 1972), pp. 46-49, for a summary of cartographic wobble, however, according to Thompson's di­ practices of the ancient world. ary: "Tuesday, Sept. 24. Got good observation. 2. Derek Howse, Greenwich Time and the Dis­ Exchanged signals with Salt Lake. Line worked covery of the Longitude (Oxford: Oxford University badly.... Friday, Sept. 27th. Exchanged sig­ Press, 1980), pp. 127-51. 3. Samuel Eliot Morison, Admiral of the Ocean nals. Got good observation and good ex­ Sea, 2 vols. (Boston: Little, Brown & Co., 1942), change."45 2:158-59. A more famous incident occurred on his fourth voyage when Columbus used a Regiomon­ Toward the end of the nineteenth century tanus-predicted, 29 February 1504, lunar eclipse to telegraphed time signals on land and cheap frighten Jamaican natives into bringing him food. Columbus used the 1504 eclipse to calculate his chronometers at sea were fast displacing old­ longitude again, and again was much too far west. fashioned almanac predictions about solar sys­ Morison explained this "inexcusable" error by theo­ tem moons as a way of measuring east-west rizing Columbus "was consciously fudging his fig­ travel. In 1905 the U.S. Navy began regular ures" to confirm his proximity to China. 2:403. 130 GREAT PLAINS QUARTERLY, SPRING 1993

4. Ernst Zinner, Regiomontanus: His Life and 11. Ian Ridpath, ed., Norton's 2000.0 Star Atlas Work (Amsterdam: Elsevier Publishers, 1990 and Reference Handbook, 18th ed. (New York: John translation by Ezra Brown of the 1968 German ed.), Wiley & Sons, 1989), p. 121. p. 123. An alternative theory for Columbus's error, 12. Stillman Drake, Galileo at Work: His Scien­ ascribed to mis-timing the 1494 and 1504 eclipses, tific Biography (Chicago: University of Chicago Press, has been offered by Donald W. Olson, "Columbus 1981). pp. 193, 257-61,374. and an Eclipse of the Moon," Sky & Telescope 13. Lloyd A. Brown, The Story of Maps (Boston: ( 1992), pp. 437-40. Little, Brown & Co., 1949). See pp. 212-24 for an 5. Gary Moulton, ed., The Journals of the Lewis excellent summary of seventeenth-century scien­ & Clark Expedition, 8 vols. (Lincoln: University of tific activity at the Paris Observatory. Nebraska Press, 1983-93), 3:273-74, 280. 14. The Nautical Almanac and Astronomical 6. The Nautical Almanac's predicted eclipse Ephemeris for the Year 1805 (London: Commission­ time for Greenwich was based on apparent time, the ers of Longitude, 1801), p. 151. kind shown on a . Lewis recorded his obser­ 15. Alexander Mackenzie, Voyages from vations according to the mean time carried on his Montreal (1801; rpt. Rutland: Charles E. Tuttle Co., chronometer (Moulton, Journals, 2:412-13). Mean 1971), pp. 348-51. time, as kept by all , squares with sundial time 16. Elliott Coues, ed., The Expeditions of Zebulon on just four days a year because of the earth's non­ Montgomery Pike, 2 vols. (1895; rpt. New York: circular around the sun. At Fort Mandan Lewis Dover Publications, 1987). See 2:564for Wilkinson's calculated that his chronometer was running about instructions; 2:851-52 for Pike's navigational ac­ an hour too slow on mean time, based on solar counting. measurements he made thirteen days later. After 17. Donald Jackson and Mary Lee Spence, eds., adding this hour back, Lewis subtracted the cor­ The Expeditions of John Charles Fremont: Travels from rected mean time of his eclipse-end observation 1838 to 1844 (Urbana: University of Illinois Press, from the Nautical Almanac's Greenwich apparent 1970), p. 482. time of the same event. This produced his recorded 18. Charles Preuss, Exploring with Fremont, trans. time difference of 6h 37m 45s, which converts to Erwin and Elisabeth Gudde. (Norman: University 99°26'45" of longitude. However, he should have of Oklahoma Press, 1958), p. 92. made an additional subtraction of 9m 56s (the 19. Eric G. Forbes, The Birth of Scientific Navi­ "" indicated in the almanac for 15 gation (Greenwich: National Maritime Museum, January) to put his mean-time observation on the 1974), p. 9. In recognition of Tobias Mayer's work same basis as the Greenwich apparent-time predic­ with lunar motions the British Parliament awarded tion. his widow £3000 in 1765. 7. That other Norsemen later retraced Leif 20. Nautical Almanac for 1805, p. 159. Ericsson's route from Greenland to America is made 21. D.H. Sadler, Man Is Not Lost-A record of clear in the "Graenlendinga Saga" in Magnus 200 years of astronomical navigation with the Nautical Magnusson and Hermann Palsson, trans., The Vinland Almanac, 1767-1967 (Greenwich: National Mari­ Sagas: The Norse Discovery of America (London: time Museum, 1968), p. 13. Penguin Books, 1965), pp. 59, 64-65. 22. W. Kay Lamb, ed., George Vancouver-A 8. IsaacJ. Cox, ed., The Journeys of Rene Robert Voyage of Discovery to the North Pacific Ocean and Cavelier Sieur de laSalle, as related by his faithful Round the World, 1791-1795,4 vols. (London: The Lieutenant, Henri de Tonty let al.J, 2 vols. (1922; rpt. Hakluyt Society, 1984), 1:4. New York: AMS Press, 1973), 1:146, 166. 23. For a revealing study of the accuracy of 9. Edmond Halley's "Magnetic Variation Chart position-fixing in 1792, see N. W. Emmott, "Cap­ of the World" is reproduced in Eva G.R. Taylor, The tain Vancouver and the Lunar Distance," Royal Haven-Finding Art (New York: Abelard-Schuman Institute of Navigation The]ournal of Navigation 27 Ltd., 1957), p. 252. (no. 4, October 1974): 490-95. Vancouver and his 10. Henri Joutel, a soldier who kept the princi­ practiced team of professional navigators, using the pal journal of LaSalle's 1684 voyage to the Gulf of world's best equipment, took multiple lunar dis­ Mexico, reported the convoy reached a longitude of tance measurements at Discovery Bay on Puget 285°16' on 20 December. Cox, Journeys of laSalle Sound, near modern Gardiner, Washington, get­ (note 8 above), 2:20. Joutel didn't say what base ting a longitude of 122°37'41" W. That was too far meridian this was measured from, but on Guillaume east by more than 11 miles, but Emmott rated the de l'Isle's 1718 map of Louisiana, which counted result "extremely good" in light of the method's longitude eastward around the world from the Ca­ imprecision. naries, it would have placed the convoy almost 24. John Garnett to Robert Patterson, 14 Janu­ directly south of the Mississippi's mouth. ary 1802, and 12 October 1804, Patterson Papers, HOW FAR WEST AM I? 131

American Philosophical Society Library, Philadel­ 35. Jefferson's instructions to Lewis, 20 June phia. Because of persistent typesetting errors in 1803, in Jackson, Letters (note 28 above), 1:62. his pirated New Jersey copies, Garnett by 1818 was 36. Moulton, Journals of the Lewis and Clark asking British authorities for permission to import Expedition (note 5 above), 2:228. wholesale lots of the Nautical Almanac directly 37. Ernest Staples Osgood, ed., The Field Notes from its London publisher, according to correspon­ of Captain William Clark (New Haven: Yale Univer­ dence in the Royal Greenwich Observatory ar­ sity Press, 1964), p. 259. chives at Cambridge University. 38. The set on Greenwich 25. A.P. Nasatir, ed., Before Lewis and Clark, 2 time proved accurate for getting longitudes on the vols. (1952; rpt. Lincoln: University of Nebraska late eighteenth century voyages of Captain James Press, 1990), 2:417,445. Cook. Not until the mid-nineteenth century, how­ 26. Richard Glover, ed., David Thompson's Nar­ ever, did cheaper, sturdier models permit wider rative 1784-1812 (Toronto: The Champlain Soci­ acceptance among sea captains and land explorers ety, 1962), p. 179. alike, with lunar distances still being used to cross­ 27. Gary Moulton, ed., Atlas of the Lewis & check their results. In response to the growing use of Clark Expedition (Lincoln: University of Nebraska chronometers, the British Nautical Almanac in Press, 1983), p. 5. 1834 started predicting celestial events according 28. Andrew Ellicott to Thomas Jefferson, 6 to mean, or clock, time instead of apparent, or March 1803, in· Donald Jackson, ed., Letters of the sundial, time. Sadler, Man is Not Lost (note 21 Lewis and Clark Expedition, 2nd ed., 2 vols. (Ur­ above), p. 12. Thereafter "" bana: University of Illinois Press, 1978), 1:23-24. became a familiar expression for navigators. The 29. Jackson, Letters (note 28 above), 1:96. U.S. Navy began publishing its annual American 30. Nevil Maskelyne, Tables Requisite to be used Ephemeris and Nautical Almanac in 1852. Today the with the Nautical Ephemeris (London: Commission­ U.S. Naval Observatory and the Royal Greenwich ers of Longitude, 1802), p. 38. Observatory jointly produce their annual ephemeri­ 31. Most of the Nautical Almanac's nine navi­ des under a common title, The Astronomical Alma­ gational stars are first-magnitude beacons chosen nac. because they lie nearly in the moon's orbital path 39. Moulton, Journals of the Lewis & Clark Expe­ around the earth. Maskelyne's list was an inconsis­ dition (note 5 above), 5:98-99. tent mix of traditional names and "scientific" 40. Ferdinand Rudolph Hassler to Robert Greek letter designations based on the constella­ Patterson, 12 August 1810, in Jackson, Letters (note tions where the stars are found. Spica, Antares, 28 above), 2:556-59. and Alpha Aquilae (traditional name Altair) were 41. Jefferson to Jose Correa de Serra, 20 July the lunar distance target stars most often used by 1816, and to William Clark, 8 September 1816, in Lewis and Clark, partly because they're conven­ Jackson, Letters (note 28 above), 2:618-19. ient for evening viewing during the warm travel 42. Report of Capt. John Pope, Red River-Rio . Grande Route, Reports of Explorations and Surveys 32. One of the popular lunar distance manuals to Ascertain the Most Practicable and Economical was compiled by Andrew Mackay, The Theory and Route for a Railroad from the Mississippi River to the Practice of Finding the Longitude at Sea or Land, 3rd Pacific Ocean, 1853-1854, 12 vols. (Washington: ed., 2 vols. (London: Longman, Hurst, 1810). An House of Representatives, Executive Document No. interesting history of lunar distance navigation is 91) 2:1-2. found at 1:92-95. 43. Isaac Stevens to Jefferson Davis, 4 August 33. Edwin James, Account of an Expedition from 1854, in Pacific Railroad Reports (note 42 above), Pittsburgh to the Rocky Mountains, 2 vols. (1823; rpt. 1:450. Ann Arbor: Readex Microprint Corp., 1966). Lieu­ 44. J.W. Powell, The Exploration of the Colorado tenant J.D. Graham's description of lunar distance River and its Canyons (1875; rpt. New York: Penguin calculations is on p. vi of his preface to the Books, 1987), pp. 119, 183. Powell (p. 237) also expedition's astronomical records, vol. 2. reported trying on 7 August 1869, to get his longi­ 34. From Lewis's unpublished "Astronomy tude from an almanac-predicted eclipse of the sun, Notebook" written mainly by Robert Patterson, but the event was clouded out. Western Historical Manuscript Collection, State 45. Herbert L. Gregory, ed., "Diary of Almon Historical Society of Missouri, Columbia, quoted Harris Thompson," Utah Historical Quarterly 7 (nos. with permission. Patterson's "Problem 4th" and 1, 2, and 3, January, April, and July, 1939): 100. "Problem 5th" told Lewis how to avoid taking the 46. Howse, Greenwich Time (note 2 above) p. altitudes of lunar distance targets. 163-64.