Curiosities of science past and present : a book for old and young / by John Timbs.
- John Timbs
- Date:
- 1875
Licence: Public Domain Mark
Credit: Curiosities of science past and present : a book for old and young / by John Timbs. Source: Wellcome Collection.
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![The account of the trial of Harrison's watch is very interesting. In April 1766, by desire of the Commissioners of the Board, the Ix)rd3 of the Admiralty delivered the watch into the custody of the Astronomer- Koyal, the Rev. Dr. Nevil Maskelyne. It was then ])laced at the lioyal Olwervatory at Greenwich, in a box having two different locks, fixed to the floor or wainscot, with a plate of glass in the lid of the box, so that it might be compared as often as convenient with the regulator and the variation set down. The form observed by Mr. Harrison in winding up the watch was exactly followed ; and an officer of Greenwich Hospital attended every day, at a stated hour, to see the watch wound up, and its comparison with the regulator entered. A key to one of the locks was kept at the Hospital for the use of the officer, and the other re- mained at the Observatory for the use of the Astronomer-Koyal or his assistant. The watch was then tried in various positions till the beginning of July; and from thence to the end of February following in a horizontal position with its face upwards. The variation of the watch was then noted down, and a register was kept of the barometer and thermometer ; and the time of comparing the same with the regulator was regularly kept, and attested by the Astronomer-Royal or his assistant and such of the officers as witnessed the winding up and comparison of the watch. Under these conditions Harrison's watch was received by the Astro- nomer-Royal at the Admiralty on May 5, 1766, in the presence of Philip Stephens, Esq., Secretary of the Admiralty; Captain Baillie, of the Royal Hospital, Greenwich ; and Mr. Kendal the watchmaker, who accom- panied the Astronomer-Royal to Greenwich, and saw the watch started aud locked up in the box provided for it. The watch was then com- pared with the ti'ansit clock daily, and wound Tip in the presence of the officer of Greenwich Hospital. From May 5 to May 17 the watch waa kept in a horizontal position with its face upwards; from May 18 to July 6 it was tried—first inclined at an angle of 20*^ to the horizon, with the face upwards, and the hours 12, 6, 3, and 9, highest successively ; then in a vertical position, with the same houi-s highest in order; lastly, in a horizontal position with the face downwards. From July 16, 1766, to March 4,1767, it was always kept in a horizontal position with its face upwards, Ijdng upon the same cushion, and in the same box in which Mr. Harrison had kept it in the voyage to Barbadoes. From the observed transits of the sun over the meridian, according to the time of the regulator of the Observatory, together with the at- tested comparisons of Mr. Harrison's watch with the transit clock, the watch was found too fast on several days as follows: h. m. B. 1766. May 6 too fast 0 0 16 2 .. 17 .. 0 3 51-8 July 6 Aug. 6 Sept. 17 Oct 29 Dec. 10 1767i Jan. 21 March 4 0 14 14 0 0 23 58 4 0 32 15 6 0 42 20 9 0 54 46 8 1 0 28 6 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 foUows:](https://iiif.wellcomecollection.org/image/b21497424_0242.jp2/full/800%2C/0/default.jpg)
