The Principles of Mr. Harrison’s Time-Keeper, with plates of the same. Published by Order of the Commissioners of Longitude.

London: W. Richardson and S. Clarke for John Nourse and Mess. Mount and Page, 1767.

First edition, probably a unique trial copy on special paper in the oblong format with plates unfolded (see below for details), of the “description of the famous solution to the centuries-old world-wide problem of finding the longitude” (Grolier/Horblit). “Harrison’s chronometer not only supplied navigators with a perfect instrument for observing the true geographical position at any moment during their voyage, but also laid the foundation for the compilation of exact charts of the deep seas and the coastal waters of the world … There has possibly been no advance of comparable importance in aids to navigation until the introduction of radar” (PMM 208). In 1714 the Board of Longitude offered a reward of £20,000, a colossal sum at the time, to anyone who could find a reliable and accurate method for determining longitude at sea. In 1730 the clockmaker John Harrison (1693-1776) completed a manuscript describing some of his chronometrical inventions, including a chronometer “accurate enough to measure time at a steady rate over long periods, thus permitting the measurement of longitude by comparison of local solar time with an established standard time” (Norman). On the strength of his descriptions, Harrison obtained a loan from George Graham, a leading maker of clocks and watches, for the construction of his timekeeper. After numerous attempts, most of which either Harrison himself or his son William tested on ocean voyages, Harrison succeeded in constructing a chronometer ‘H4’ that was both accurate and convenient in size. Following successful tests on voyages to the West Indies in 1761 and 1764, Harrison felt that he had a right to the prize, but the Board of Longitude hedged, insisting on a demonstration and full written description of his invention. The demonstration took place on 22 August 1765, in the presence of the astronomer-royal Nevil Maskelyne and a six-member committee of experts appointed by the Board. The results were written up and published in this pamphlet by Maskelyne, along with Harrison’s own description of his timekeeper. Officially the Board intended Principles to enable other clockmakers to construct H4, but it “was both incomplete of enough information to allow the duplication of the watch … and contain[ed] some accidentally-on-purpose errors. This was likely done as much to help maintain the hard-won knowhow of its inventor, as well as to protect any military advantage, given the importance of the H4 to maritime navigation” (Lake).

Printing: Maskelyne’s Preface explains how he had a few copies done himself with the plates on India paper. These special copies were done in oblong format so that the plates did not have to be folded. The ordinary copies were done in normal 4to format and all the plates had to be folded: “for the sake of the curious, and particularly artists who may be desirous to construct other watches after the model of Mr. Harrison’s, I have caused a few impressions of the plates to be taken off upon India paper; which, if it be made only a little damp, by being put for a few minutes between two wet sheets of paper, will receive the impression from the plates perfect, and will not shrink at all in the drying” (p. vii). Our copy is in the rare oblong format and plates unfolded but is not on India paper. Our copy is on paper with no watermarks. Ordinary copies, with the plates folded, are on paper with watermarks. The special copies with the plates on India paper do not have watermarks. Thus this seems to be a kind of hybrid on special, but not India paper, and in the rare oblong format with plates unfolded.

“In the early 1700s, European monarchies aspired to power by building world-spanning networks of colonies and commercial ventures. As a result, the merchant fleets and navies that connected and protected these assets were critically important. Eighteenth-century sailors led dangerous lives, not least because they seldom knew their exact location on the open ocean. Although navigators readily determined latitude, or north-south position, by estimating the height of certain stars at their zenith, they could not determine longitude. This failure caused shipwrecks that killed thousands of mariners and lost cargoes worth fortunes. Several countries offered immense financial rewards for a solution to the problem; Britain promised £20,000 (several million dollars in today's currency) for a way to establish longitude to within half a degree (30 nautical miles at the equator) after a journey from England to the West Indies. To judge proposed solutions, the crown established a Board of Longitude, made up of the Astronomer Royal, various admirals and mathematics professors, the Speaker of the House of Commons and 10 members of Parliament.

“In effect, determining longitude depended on knowing the difference between local time and the time in Greenwich, site of the Royal Observatory. In principle, if a ship had a clock keeping Greenwich time, the navigator could measure the angle of the Sun to note local noon and compare it to the clock. If the clock read 2 p.m., his longitude was two hours, or 30 degrees, west of Greenwich. The problem lay in finding a clock reliable enough to keep time during the long voyages of that era. The best pendulum clocks of the day were accurate enough, but were useless on a heaving ship at sea. Alternately, a less reliable clock might be used if some means could be devised to correct it frequently. In practice this meant an astronomical method, the best of which became known as the method of lunar distances, in reference to the fact that the Moon's orbit causes it to continually change position in the sky. For example, a new moon, which appears close to the Sun, will have moved 180 degrees by the time it becomes a full moon two weeks later. The idea was for astronomers to provide tables of this angle between Moon and Sun (or Moon and selected stars in the night sky) as a function of Greenwich time. A measurement of this angle every few days would provide a correction to the mechanical clock. This scheme had two drawbacks: The first was that, at least initially, astronomers could not accurately predict the Moon's motion; the second was that the mathematical calculations required of the mariner were very complex—they took hours, and errors were common.

“The chronometer and the method of lunar distances each had their proponents, and the solution of the longitude problem came down to a bitter battle between two Englishmen: John Harrison, a self-educated machinist who set out to make an accurate clock, and Nevil Maskelyne, astronomer and scion of the Church of England, who brought the method of lunar distances to fruition.

“John Harrison was born in Yorkshire and followed his father's trade as a carpenter. This led to an interest in wooden (pendulum) clocks, which he became adept at making. His isolation from other clockmakers during this formative time was fortuitous—when most clockmakers learned that the prize required their clocks to maintain a rate constant to within three seconds per day for six weeks at sea, they regarded the task as impossible. Harrison saw it as a challenge, and developed the technical advances that justified his confidence, including the so-called gridiron pendulum (which used metals with different expansion coefficients to overcome temperature sensitivity), a nearly frictionless gear system and a ratcheted spring that kept the clock running while being rewound.

“By 1728 the longitude prize had been open for 14 years without a serious contender. Young Harrison journeyed to London to learn about the award and met Edmond Halley (1656-1742), the Astronomer Royal. Halley treated him cordially and suggested that Harrison consult George Graham (1673-1751), one of London's leading clockmakers. Harrison and Graham took an immediate liking to each other—they talked for 10 hours that day, leaving Graham so impressed that he offered to lend Harrison money (without security or interest) to develop the young inventor's ideas.

“Seven years passed before Harrison offered a solution to the problem: the clock later known as H1. It was cumbersome and heavy, with jutting arms and counterweights, but a small committee of the Royal Society, including Halley and Graham, declared it a masterpiece of ingenuity and urged submission to the Board of Longitude. This body, ever skeptical after years of spurious claims, proposed a short sea trial before attempting the expensive, official crossing of the Atlantic. So Harrison and H1 embarked on a run to Lisbon and back. The numerical result of the clock's performance has not survived, but the captain was very impressed. The ship's navigator admitted that on the return voyage, just before the English coast was sighted, his own calculations put them more than 90 miles offshore, while Harrison maintained that no, they were just about there.

“Although the voyage didn't immediately lead to a trans-Atlantic test, it was productive for Harrison, who identified several potential improvements to H1. With these in mind, he withdrew his initial submission and set about building a second clock (H2). The Board of Longitude, impressed by H1, awarded Harrison £500 toward development expenses. He completed H2 three years later and spent two more years testing it on land. By 1741, testing was complete, but England was at war with France and her allies. No one was prepared to risk a sea trial of H2 and possible capture by the French. As it turned out, H2 was never tested at sea.

“While waiting for the war to end, Harrison built a third clock, with the Board of Longitude contributing another £500 to meet his costs. But this time, Harrison's expertise failed him. H3 never worked to Harrison's satisfaction, and he abandoned it after five years. Taking a different tack, he proposed in 1746 to build two more clocks. Of these, H4 would be his masterpiece. It took another 13 years to complete, but was quite different from its predecessors. Instead of being all angles and arms, it appeared as a beautifully encased pocket watch, albeit five inches in diameter. After two years of testing the Board accepted it for the full trans-Atlantic test.

“Harrison, now 68, left H4 in the care of his son William for the long voyage in 1761. The trial ended upon reaching Jamaica, where, amazingly, H4 reported the longitude with less than two miles of error. Back in England, the overjoyed Harrisons awaited their award of £20,000. Then everything started to go wrong. The Board of Longitude refused to believe the test results were not just a stroke of luck and demanded a second trial. The Harrisons protested vehemently. They had met the terms of the prize and now they wanted it. Uproar ensued, and to quell it, Parliament offered William Harrison £5,000 for results so far, in return for full disclosure of the construction details of H4. William refused this partial award and decided to attempt a second trial in 1764, this time to Barbados.

“The Reverend Nevil Maskelyne now enters the story. He had no particular influence prior to this stage of Harrison's odyssey, but the Board of Longitude made a decision that quickly embroiled him in the controversy. Although Maskelyne was not then a member of the Board of Longitude, he was a Fellow of Trinity College, Cambridge, and a Fellow of the Royal Society. For some years he had maintained a strong interest in, and advocacy of, the method of lunar distances for determining longitude. Furthermore, as Tobias Mayer (1723-62) in Germany had recently resolved the problem of predicting the motion of the Moon, the method was ripe for testing. Thus, when the Board of Longitude asked Maskelyne to join the voyage to Barbados, primarily to establish the longitude of the capital, Bridgetown, by observation of Jupiter's satellites, he was also to test the method of lunar distances and its accuracy compared to Harrison's H4 clock.

“The results were announced at a memorable meeting of the Board of Longitude in early 1765. H4 had done it again, producing the Bridgetown longitude with less than ten miles of error after a journey of more than 5,000 miles. The rival method of lunar distances fared slightly worse, yielding the result to "better than 30 miles." By way of explanation, four of the ship's officers at the meeting stated that their calculations were a product of Maskelyne's instructions, and, by implication, subject to their own inexperience. In any case, since the lunar distance method depended on tables that only Maskelyne could calculate, the method was not yet ready to claim the prize.

“The Board of Longitude accepted the result of the Barbados trial of H4, but they remained unconvinced that the instrument was not just a fluke—a one-off that might never be replicated. Parliament passed a new Act that yielded £10,000 to Harrison but withheld the remaining half of the prize until he met a series of conditions. According to Parliament's terms, Harrison had to reveal in writing exactly how the watch had been made, including full drawings of each part and explanation of every detail to a select team of watchmakers. Then he needed to wait for these persons to manufacture similarly accurate watches themselves. Moreover, Harrison was compelled to relinquish H4 to the Astronomer Royal for long-term checking of its accuracy.

“Here was the rub: Two Astronomers Royal had died in rapid succession, and no sooner had Maskelyne returned from Barbados than the King [George III, 1738-1820] appointed him to the position; the appointment automatically put him on the Board of Longitude. As a result, Harrison's nemesis not only became an influential voice on the Board of Longitude but also took charge of checking his best clock. Not surprisingly, the resulting report on H4 was entirely negative. It seems Maskelyne prevaricated over the meaning of “accuracy” to condemn Harrison's creation. In this era, all clocks gained or lost time at some rate, but so long as that rate was constant and known, one could derive an accurate time. Maskelyne refused to allow these corrections.

“While waiting for the copies of H4 to be completed, Harrison spent three precious years building H5—now approaching 80, he was becoming increasingly desperate. As the Board of Longitude debated sending his watch to the arctic and elsewhere for lengthy tests, Harrison appealed to King George III for help. The King had H5 installed at his own personal observatory at Kew, and he himself supervised its daily winding and checking. Under his care, H5 performed so admirably that “Farmer George” was outraged by what had gone before. “By God, Harrison,” he roared, “I'll see you righted!” and threatened to appear in person before Parliament (under a lesser title, of course).

“So the affair finally wound down. The Board of Longitude, under the continuing influence of Nevil Maskelyne, still managed to find reasons to withhold some of Harrison's prize money. Nevertheless, including interim advances, he received a total of £23,065 from the Board over four decades. A copy of H4 made by another watchmaker accompanied Captain James Cook (1728-79) on his second voyage to the Pacific, where it was hailed as having “an amazing degree of accuracy,” although Cook also used the lunar distances method with good results. In a triumph of his own, Maskelyne had initiated the annual publication of The Nautical Almanac, which included the necessary tables for applying that method. Cook referred to it as “our faithful guide through all vicissitudes of climates.” And since sufficiently accurate clocks (later called marine chronometers) remained very expensive for a long while, the method of lunar distances remained in use for more than a hundred years.

“Harrison died in 1776, unreconciled with Maskelyne to the end. One cannot blame him, but because it turned out that posterity owed much to both of them, it would have been pleasing had their relationship ended otherwise” (J. Donald Fernie, ‘The Harrison-Maskelyne Affair,’ American Scientist 91 (2003), 403-5).

Baillie, p. 272; Crone 564; Grolier/Horblit 42b; Norman 995 (all the regular 4to issue). Lake, ‘In-Depth: The Microscopic Magic of the H4, Harrison’s First Sea Watch’ ( See Lake for a detailed account of the construction of H4.

Oblong 4to (282 x 225 mm), pp. xvii, [1, blank] (v-viii: Preface; ix-xvii: ‘Notes taken at the discovery of Mr. Harrison's time-keeper’, both by Maskelyne), 19-31 (19-21: general account of H4; 22-31: description of the plates, both by Harrison), with 10 engraved plates, one double-page folding. Contemporary marbled wrappers, uncut. An excellent copy, preserved in a morocco-backed box.

Item #4835

Price: $135,000.00