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Chapter 21

This webpage reproduces a chapter of
Truxtun of the Constellation

by
Eugene S. Ferguson

published by
The Johns Hopkins Press
Baltimore, Md.
1956

The text is in the public domain.

This page has been carefully proofread
and I believe it to be free of errors.
If you find a mistake though,
please let me know!


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Chapter 23

This site is not affiliated with the US Naval Academy.

p103 Chapter 22

Navigator

Although the Navy had first call on his time, Captain Truxtun somehow managed to ready a manuscript for the printer during the p104summer of 1794. It was a book on navigation, designed to supply some of the deficiencies and omissions of standard works on the subject.1 This was five years before publication of the first American edition of John Hamilton Moore's New Practical Navigator, with corrections and emendations by Nathaniel Bowditch; and eight years before Bowditch published his own New American Practical Navigator. Moore, a British author, was in 1794 the reigning authority in Britain and America.

Captain Truxtun submitted his work to the Reverend Doctor John Ewing, President and Professor of Natural Philosophy of the University of Pennsylvania, Fellow of the American Philosophical Society, and authority on astronomy, for his "candid opinion" of its worth. He was publishing it, he said, in order to be "useful to the public" and with the idea that nautical information should be "more generally diffused, and more clearly understood by the present rising generation of seamen."

Professor Ewing's response was somewhat less than candid, but it made pleasant reading. He had no suggestions for improvement; he simply hoped that the book would have a "desireable tendency to promote the useful and important art of navigation." Being a theorist, he said, he could hardly hope to add anything to a work by "a gentleman of experience, in every situation of seas, wind, and weather; and who has justly acquired the character of the first navigator that has ever sailed from the ports of the United States."

"I very well know," he added, "the indolence of masters of vessels, and their aversion to the trouble of calculation, when they apprehend themselves able, by the common mechanical mode of conducting a vessel, after many circuitous windings, to reach an intended port."2

When the master of a ship could take her out of an American port, sail half way around the world, and then confidently expect to return once more to the very port from which he sailed, he must know something about navigation, even though it might be only the "common mechanical mode of conducting a vessel." Almost all mariners at this time could find their latitude at sea by measuring the altitude, or angle above the horizon, of the noonday sun or of the pole star; but to fix one's position in longitude was to most of them one of the unsolved riddles, on a level with perpetual motion.

The usual approach to the problem of navigating a vessel over long distances at sea was by dead reckoning. In dead reckoning, the navigator p105kept an approximate record of time, course, and speed. Each day he laid down on his chart the courses and distances run, and from these he could deduct his position. This method had grave disadvantages, however, and steered many a stout vessel onto unexpected rocks and shoals. After a long voyage, the only safe way to approach a coast was to sail during daylight hours, keeping a sharp lookout ahead and a deep sea lead sounding for bottom, and then to cease all progress at nightfall, lie to, and wait for the sunrise once more.

Captain Truxtun, when he brought Benjamin Franklin home from France, navigated by dead reckoning. After he had been out of sight of land for more than a month, he overtook another vessel that had been at sea for about the same length of time. He asked her what longitude she made and then compared his own figures with hers. They disagreed by four degrees, nearly two hundred miles. Two days later, thinking that he was still over a day's run from the Delaware capes, he spoke two whalers from New York, who informed him that he was almost on soundings. When he took a pilot on board, he found that his actual position was more than two hundred miles farther west than he thought it was. On the other hand, the vessel he had overtaken had been nearly four hundred miles from her calculated position.3

Errors in dead reckoning were easily made and accumulated rapidly. For example, there was no simple way to correct for drift of a vessel due to ocean currents. The navigator could determine approximately how fast he was moving through the ocean, but he could not tell how fast the ocean was moving. Even without any drift, the gauging of speed was subject to gross errors. Speed was determined by a chip log. The chip, a triangular piece of wood weighted at one end, was fastened to the end of a reel of light log line, the line having knots tied in it at uniform intervals. A sand glass completed the necessary equipment. The log was heaved out astern, the log line was paid out freely, and the number of knots that came off the reel while the sand ran through the glass was counted. The sand glass was usually timed at twenty-eight seconds; the number of knots dragged out by the nearly stationary chip in twenty-eight seconds could then be converted to a rate of speed. But either the line or the glass might be in error. The Empress of China had once made land two days before she expected to, because a twenty‑eight-second glass p106actually measured only twenty-five, an error of more than ten per cent.4

Captain Truxtun realized, when he entered the China trade, that he would be able to make quicker and safer passages if he knew something about celestial navigation. Accordingly, he purchased books and tables published by the British Commissioners of Longitude — "for no others are sufficiently exact," he wrote, "or printed with equal care" — procured a first‑hand sextant, and then assiduously applied himself to unraveling the mysteries of finding the longitude at sea.5

The now‑famous John Harrison chronometer Number 4 — this Englishman had spent most of his life building and perfecting his timekeepers — had been proven in 1762, during a 6,000 mile voyage, to be an accurate and dependable instrument. However, chronometers had not by 1794 been generally adopted for use at sea, and they would not be for another thirty or forty years.6 Moore and Bowditch each devoted little more than a page to finding the longitude by chronometer. In both works, the recommended approach to the problem was to use "Lunar Observations." This method involved the measurement of angular distance between the sun and moon or between the moon and a fixed star. After measuring this angle and checking local time — the latter a relatively simple task — the navigator could, by us the British tables, work out his longitude. However, the observation of angle had to be made with "the greatest imaginable nicety," because an error of observation of one minute of arc could result in an error of position of almost thirty miles.7 Also, the required calculations were formidable. When Captain Truxtun wrote his book, he was one of perhaps less than half a dozen Americans who could fix his longitude "within a very few miles, (often within five miles, and always within fifteen)."8 It was more than a generation before the practice of celestial navigation became general in American ships.9 An officer in the Navy during the early eighteen-hundreds recalled later that "Chronometers were unknown . . . sextants were very rare, and their use still more so. The navigators who could ascertain the longitude by lunar observations were few in number, and the process of calculations a mystery beyond ordinary attainments."10

There were no new theories or methods presented in Captain Truxtun's book; nor did he pretend that there were. He called the p107book simply "Remarks, Instructions, and Examples relating to the Latitude & Longitude"; feeling that it was necessary to provide numerous worked‑out examples that the neophyte might use as a guide while he followed the standard instructions, and to caution him against some of the errors he might make when he used methods outlined in the British works. He included an essay on the use and care of instruments, one on the "Variable Winds, Trade Winds, Monsoons, Hurricanes, Tornadoes, Tuffoons [typhoons], Calms, Currents and Particular weather met with" on his Oriental voyages, and a chart of the world, which he "caused . . . to be engraved, at a great expence," and on which he laid down the course of the Gulf Stream and the routes he had followed to China and India.11

Bowditch, in his New American Practical Navigator, first published in 1802, wrote, "We are chiefly indebted to Doctor Franklin, Commodore Truxtun, and Jonathan Williams, for the knowledge we possess of the direction and velocity of this stream. . . . They all concur in recommending the use of the thermometer, as the best means for discovering when you are in or near the stream."12

An appendix to Captain Truxtun's book included a system of masting that he had worked out and an outline of the general duties of officers of ships of war, for the information of other officers in the Navy. In its final form, this compendium of naval lore was impressive. It filled a folio-size volume of about a hundred and twenty pages; it displayed an extensive understanding of marine arts and science; and it represented an immense amount of work.

Undoubtedly, he expected some recognition for this enterprise. When at length it was published, he sent copies of his book to men high in the national government — the Secretary of State, among others — and he probably directed a copy to the President's attention.13 He gave the Secretary of War enough copies to distribute to each of the other naval captains.14 But it would be ungenerous to say that his book was produced with the aim of impressing his seniors; he wanted as well to instruct and inform his juniors. Later on, many members of the rising generation of naval officers, at least on board Captain Truxtun's ships, spent untold hours struggling through examples that paraded parallax and refraction up one side of the page and six‑place logarithms down the other. As for the system of masting and general duty of officers, he wanted the Navy to be a closely knit organization, whose aims and procedures were p108uniform and generally understood throughout the service. He did not expect his work to be definitive; he invited discussion and comments; but he recognized that talk of improvement was idle unless there was first something to improve.


The Author's Notes:

1 Thomas Truxtun, Remarks, Instructions, and Examples, Relating to the Latitude and Longitude (Philadelphia, 1794).

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2 Ibid., pp. * 5‑* 7.

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3 APS: Franklin-Bache Papers, Diary of Benjamin Franklin Bache; Benjamin Franklin, Writings, A. H. Smyth, ed. (New York, 1905‑1907), IX, 412.

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4 Josiah Quincy, Journals of Major Samuel Shaw (Boston, 1847), p210.

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5 Truxtun, op. cit., "Lunar Observations," p3.

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6 According to A. Wolf, A History of Science, Technology, and Philosophy in the Eighteenth Century (2nd ed., London, 1952), p159, Royal Navy vessels were furnished with chronometers from about 1825. On the initial success of Harrison's chronometer, see D. C. Holly, "All for the Purpose of Marking Time," U. S. Naval Inst. Proc., LXXIX (March, 1953), 303‑309.

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7 Truxtun, op. cit., "Lunar Observations," pp3‑6; "Navigation," Encyclopedia Britannica, 11th ed.

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8 Truxtun, op. cit., p. * 5.

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9 Samuel Eliot Morison, Maritime History of Massachusetts, 1783‑1860 (Boston, 1921), pp114‑16.

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10 Autobiography of Commodore Charles Morris, USN (Annapolis, 1880), p12.

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11 The similarity between this chart of the world and the one in William Guthrie, Maps Belonging to Guthrie's System of Geography (London, 1786), must be remarked. The engraver apparently copied Guthrie's chart.

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12 Nathaniel Bowditch, The New American Practical Navigator (First ed., Newburyport, 1802), p235.

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13 LC: Washington Papers, vol. 274, Truxtun to Edmund Randolph, July 27, 1795.

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14 Navy 1790‑98 LB, p103.


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