258 The Proposed Pendulum Operations for India. [No. 4, 



off on them a scale, transferred from Colonel Lambtons's scale ; the 

 length was then measured by a pair of beam compasses. The length 

 of the seconds pendulum was found to be 39.0263 inches of this 

 scale in air. 



In 1818, Captain Kater published his determination of the length 

 of the seconds pendulum in London at Mr. Browne's house, Portland 

 Place, taken for the purpose of fixing the standard of English 

 measures. His method was founded on the dynamical theorem due to 

 Huyghens, that the centre of oscillation, and axis of suspension, are 

 reciprocal in the same body ; that is, if the body be suspended at its 

 centre of oscillation, the former axis of suspension will pass through 

 the new centre of oscillation, and the body will vibrate in the same 

 time as before. The distance from the axis of suspension to the point 

 called centre of oscillation, is equal to the length of the simple 

 pendulum. 



In 1822, the English Government sent out an expedition under 

 Captain, now General, Sabine, for the purpose of extending the 

 enquiry commenced by Captain Kater ; for both Kater and Biot had 

 come to the conclusion, from a discussion of their experiments, that 

 no decisive result of the earth's ellipticity could be obtained from 

 them, on account of the smallness of the comprised arc, and the 

 variations of local density. Captain Sabine visited thirteen stations 

 between Bahia, S. Lat. 12° 59' to Spitzbergen N. Lat. 79° 50'. 

 He had with him three pendulums of Kater's invariable pattern, 

 which were all swung at each station. Besides these he had the two 

 clocks and attached pendulums which he had already used on his 

 arctic voyages. His method of observation was similar to Captain 

 Kater's ; all the pemhilums were swung in London at Mr. Brown's 

 house, both before and after the expedition. 



Captain Sabine subsecpiently determined the difference in the 

 number of vibrations made by an invariable pendulum between London 

 and Paris, London and Greenwich, and London and Attona. He also 

 determined the true buoyancy correction for Kater's convertible 

 pendulum. 



In 1825 M. Bessel made his experiments for determining the length 

 of the seconds pendulum at Konigsberg, with an apparatus constructed 

 and partly designed by Repsold the celebrated artist of Hamburg 



