235 



As the difference given by theory is 0*000716, the agreement 

 may be regared as satisfactory. 



The second method admits of far greater exactitude. Two similar 

 pendulums, but differing somewhat in length, were suspended in the 

 plane of the meridian at 7 decims. distance from each other. The 

 distance of the point of suspension from the centre of the weight 

 amounted, in the long pendulum, to 10,216 millims., and in the 

 short pendulum to 10,115. The conical rotations, one right and 

 the other left, were impressed upon both pendulums simultaneously, 

 and the simultaneous passage of their suspending wires across the 

 meridian was observed by a telescope, the optic axis of which, when 

 the pendulums were at rest, intersected both wires. The number of 

 oscillations n, n 1 of the two pendulums accomplished between two 

 coincidences was noted; and we thus had n'—(n-\-l), where n' 

 refers to the shorter pendulum. 



When the series was finished, the pendulums were arrested, and 

 set in motion in the opposite directions ; the coincidences were 

 again observed, and the numbers N and N' = (N + 1) were deter- 

 mined. 



Calling the latitude X, the duration of a sidereal day T, the dura- 

 tion of an oscillation of the longer pendulum released from the action 

 of the earth t, the same duration of the shorter pendulum t', then if 

 the theory be correct we must have 



sin\ 



i_/_i l_l 



-K'lw + w' N + N'J 



T t+? ln+n' N + N' 



The experiment on the 25th of May gives 



n =207'86 N=217'82 



w'=208*86 N'=218*82 



The experiment on the 10th of June gives 



n =206*31 N =215*96 



rc' = 207*31 N'=216-96. 



From these experiments we may deduce the difference in the time 

 of rotation between a right- and left-handed motion ; applying the 

 necessary corrections, we find — 



Difference on the 25th of May .... 0"'000725 

 Difference on the 10th of June .... 0"'000710. 



