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The Principles of Mr. Harrison's Time-Keeper, with plates of the same.

Published by order of The Commissioners of Longitude. [Bound with three related pamphlets.]

London: printed by W. Richardson and S. Clarke; and sold by John Nourse, and Mess. Mount and Page, 1767 Stock Code: 138402
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Harrison's determination of longitude, and related pamphlets

First edition of the primary account of the invention of the marine chronometer, which revolutionized the science of navigation. "There was no comparable advance in navigational aids until the development of radar in the twentieth century" (Norman).

In 1714, the Board of Longitude offered a substantial reward of 20,000 to anyone who could find an accurate method for determining longitude at sea. In 1730, clockmaker John Harrison completed a manuscript describing some of his 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, involving instruments in several different shapes and sizes, most of which Harrison himself or his son William tested on ocean voyages, Harrison succeeded in constructing a chronometer that was both accurate and convenient in size. The chronometer was successfully tested on two voyages to the West Indies in 1761 and 1764. Following these successful trials 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. To that end, a 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, and the present work was published. It records the results, along with Harrison's own description of his timekeeper.

Still unsatisfied, the Board awarded Harrison only half the prize money, and continued to raise obstacles, subjecting his chronometer to extreme and unrealistic tests, and requiring him to build yet two more examples. It was not until 1773, after direct intervention by King George III, that the 80-year old inventor was paid the remainder of the prize money. Several of his earliest chronometers are preserved at the Royal Observatory in Greenwich. Although Harrison's chronometer was soon supplanted by simpler mechanisms, the timekeeper "revolutionized the science of navigation, as it gave navigators their first means of observing true geographical position at any given moment during a voyage" (Norman).

The three related pamphlets bound with Harrison's work are:

i) BIRD, John. The method of dividing astronomical instruments. Published by order of the Commissioners of Longitude.

London: sold by John Nourse; and Mess. Mount and Page, 1767 (large paper issue);

ii) BIRD, John. The method of constructing mural quadrants. Exemplified by a description of the brass mural quadrant in the Royal Observatory at Greenwich. London: printed by W. Richardson and S. Clark; and sold by John Nourse; and Mess. Mount and Page, 1768;

iii) LUDLAM, William. An introduction and notes, on Mr. Bird's method of dividing astronomical instruments. To which is added, a vocabulary of English and French technical terms. London: sold by John Sewell, 1786.

Bird's mural quadrant was originally constructed to be taken on board the Endeavour in 1767. It was not in competition with Harrison's chronometer, but was vital to the entire voyage, as it was to be used to observe the transit of Venus from Tahiti, the original instruction from the Admiralty for Cook's voyage. The two pamphlets here are complementary, as the engraved plans for the quadrant are split between them, plates I-III with the first part, IV with the second. The last work in the volume is an essential addendum to Bird's work. The Cambridge mathematician William Ludlam was one of the handful of scientists who attended the Board of Longitude's 1767 interview of Harrison, and who was also present at two interviews of John Bird in 1767 and 1771. Though derided by Harrison as a "parson", Ludlam was technically competent and ideally suited to explain the technicalities of Bird's work.

The pamphlets were evidently bound up together in the 1790s, when Sir Christopher Sykes, 2nd Baronet, greatly improved Sledmere, including building two new wings to the house. The famous Long Library at Sledmere has been described as "one of the most beautiful rooms in England".

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Together 4 works bound in 1 volume, quarto (259 x 201 mm). Near-contemporary half calf (endpapers watermarked 1794), flat spine with gilt rules, green morocco title label and Sledmere House emblem in gilt on a green morocco label at foot, marbled sides.


Harrison: 10 folding engraved plates on drawing paper showing the technical details of Harrison's fourth timekeeper, H4; with the half-title. Bird's two works with a total of 4 folding engraved plates, the first with half-title as called for; no half-titl


From the library at Sledmere House in Yorkshire. Extremities rubbed, a faint spray of foxing at head of Harrison half-title and title, the contents otherwise fresh and clean throughout, a handsome volume.


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