85 



seconds in vacua, at the level of the sea, measured at the tempera- 

 ture of 62 Fahr., and the latitude of the place of observation, de- 

 duced from the data contained in the trigonometrical survey, being 

 5131'8"-4N., is, 



Inches. 



By Sir George Shuckburgh's Standard 39' 13860 



By General Roy's Scale 3943717 



By Bird's Parliamentary Standard 39-13843 



On the Length of the French Metre estimated in parts of the English 

 Standard. By Capt. Henry Kater, F.R.S. Read February 5, 

 1818. [Phil. Trans. 1818, p. 103.] 



One of the objects of the Committee of the Royal Society ap- 

 pointed 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 Metre a 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 Metre (i 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 expe- 

 riments 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 -royinnrths of an inch, that 

 the length of the Metre ti Traits, in inches of Sir George Shuck- 

 burgh's scale, is 39'37076 inches. The author next describes the 

 means resorted to for ascertaining the length of the Metre a 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 -nr.-ornrth of an inch, to be 39 '3 7081 inches 

 of Sir George Shuckburgh's standard. 



After explaining the principles upon which the column in the 

 tables intitled " Correction for Temperature" is constructed, Captain 

 Kater remarks, that we may consider the mean derived from both 

 metres, viz. 39'37079 inches of Sir George Shuckburgh's scale, or 

 39'37062 inches of Bird's parliamentary standard, as the length of 

 the French metre. 



