h. m. s. 1766. May 6 too fast 0 0 16·2 May 17 ” 0 3 51·8 July 6 ” 0 14 14·0 Aug. 6 ” 0 23 58·4 Sept. 17 ” 0 32 15·6 Oct. 29 ” 0 42 20·9 Dec. 10 ” 0 54 46·8 1767. Jan. 21 ” 1 0 28·6 March 4 ” 1 11 23·0 From May 6, which was the day after the watch arrived at the Royal Observatory, to March 4, 1767, there were six periods of six weeks each in which the watch was tried in a horizontal position; when the gaining in these several periods was as follows: During the first 6 weeks it gained 13m 20s, answering to 3° 20′ of longitude. In the 2d period of 6 weeks (from Aug. 6 to ” 8 17 ” 2 4 Sept. 17) In the 3d period (from ” 10 5 ” 2 31 Sept. 17 to Oct. 29) In the 4th period (from ” 12 26 ” 3 6 Oct. 29 to Dec. 20) In the 5th period (from ” 5 42 ” 1 25 Dec. 20 to Jan. 21) In the 6th period (from ” 10 54 ” 2 43 Jan. 21 to Mar. 4) It was thence concluded that Mr. Harrison’s watch could not be depended upon to keep the longitude within a West-India voyage of six weeks, nor to keep the longitude within half a degree for more than a fortnight; and that it must be kept in a place where the temperature was always some degrees above freezing.[57] (However, Harrison’s watch, which was made by Mr. Kendal subsequently, succeeded so completely, that after it had been round the world with Captain Cook, in the years 1772-1775, the second 10,000_l._ was given to Harrison.) In the Act of 12th Queen Anne, the comparison of chronometers was not mentioned in reference to the Observatory duties; but after this time they became a serious charge upon the Observatory, which, it must be admitted, is by far the best place to try chronometers: the excellence of the instruments, and the frequent observations of the heavenly bodies over the meridian, will always render the rate of going of the Observatory clock better known than can be expected of the clock in most other places. After Mr. Harrison’s watch was tried, some watches by Earnshaw, Mudge, and others, were rated and examined by the Astronomer-Royal.