On the length of the French mètre estimated in parts of the English standard

Abstract

One of the objects of the Committee of the Royal Society appointed for the purpose of determining the length of the seconds’ pendulum having been to compare the French Metre with the British Standard Measure, two metres were procured from Paris for that purpose; one called the Mètre à Bouts , being a bar of platinum, of which the terminating planes are supposed to be parallel, and the distance between them the length of the metre; the other termed the Mètre à Traits , consisting also of a bar of platinum, but upon which the length of the metre is shown by two very fine lines. The latter was first examined, by placing it in contact with Sir George Shuckburgh’s standard scale; their surfaces being in the same plane, and care being taken that their temperatures were alike. The same micrometer microscopes employed in the pendulum experiments were used, and were brought alternately over the metre and over the scale. It appeared from the mean result, properly corrected, of fourteen comparisons, the greatest difference between any one of which and the mean result is less than 2/10,000ths of an inch, that the length of the Mètre à Traits , in inches of Sir George Shuckburgh’s scale, is 39·37076 inches. The author next describes the means resorted to for ascertaining the length of the Mètre à Bouts ; which appears, from the results of four sets of experiments, each set consisting of five, the greatest difference between any one of which and the mean result is 1/10,000th of an inch, to be 39·37081 inches of Sir George Shuckburgh’s standard.