Pendulum Experiments on Mont Cenis^ 157 



in perfect agreement with each other : one received from Paris 

 by the Commission of Weights and Measures at Milan; a 

 second brought more recently from Paris by Conte Moscati ; 

 and a • tfl^ird - in .the i;possessioa; of the Royal Academy of 

 TuriDJ'M-xj^ii ' .i'il ;^-.! , ;,■:,. 



•I'^'be «itperiiQents were commenced on the 3rd of September, 

 add'terminated on the 27th, being interrupted by M. Carlini's 

 absence at Chambery from the 7th to the 12th. The distance 

 between the microscopes, and the oscillations and length of the 

 pendulum, were measured alternately. Thirteen independent 

 results were thus obtained, of which the greatest discordance 

 from the mean was not more than -jyV^T)^^^ ^^ ^ British inch. 

 The mean result was 39.0992 British inches, the length of the 

 pendulum vibrating seconds in a vacuum, at the place of obser- 

 vation on Moiit Cenis, 1943 metres, or 6374 feet above the 

 sea, in the latitude of 45° 14' 10". To compare with this 

 determination, we may obtain a tolerably fair approximation 

 tO' the pendulum at the level of the sea in the latitude of 

 45° 14' 10", such as its length might have been found, if the 

 mountain could have been removed and the pendulum placed 

 on its site, by deduction from the lengths actually measured 

 with a similar apparatus, on the arc between Formentera and 

 Dunkirk, at stations not far removed from the level of the sea, 

 in the adjacent parallels to Mont Cenis, and in the countries 

 adjoining. Of these there are five, not including the station at 

 Clermont, in consequence of its great elevation : they are as 

 follows : — 



Dunkirk .. 51 02 10; its pendulum at the level of ihe seat — 59.13771 

 Paris ... 48 50 14; „ „ „ „ 39.12894 



Bordeaux . 44 50 26 ; „ ^^^ to offf>'l^ 5iij» ar..^^-^^^^^ 



Figeac ... 44 36 45; „ ^ ,T ' ^"^2. ^"39.11212 



Formentera 38 39 56; „ ,» ., „ -r^ 39.09176 



The mean length of the seconds pendulum at the level of the 

 sea, in the latitude of 45° 14' 10^, deduced from these deter- 

 minations, is 39.1154 ; and it is so equally, whether an eUip- 

 ticityof^th, or of ^^th, or any intermediate ellipticity, be 

 assumed in the reduction. 

 We have, then, 39.1154 - 39.0992 = -0162 inch., as the 



