104 Astronomical and Nautical Collections, 



Ellipticity. 



From Captain Sabine's 13 stations 1 : 288-4 



From these 13 and 8 stations of the French . . 1 : 288*7 



From these 13 and 7 British stations 1 : 289*5 



From the mean of 5 stations near the equa- > , , oos«3 

 tor and 6 in Britain \ 



From the mean of 5 equatorial and the most ) , . 2 qq 4 

 northerly 5 $ 



From the 6 British and the 5 northerly .... 1 : 288-5 



From the general combination of 25 stations 1 : 289*1 



Mean T7288-7 



" The attempt," says Captain Sabine, p. 352, " to determine 

 the figure of the earth by the variations of gravity at its surface, 

 has thus been carried into full execution on an arc of the meridian 

 of the greatest accessible extent ; and the results which it has pro- 

 duced are seen to be consistent with each other, in combinations 

 too varied to admit a probability of the correspondence being acci- 

 dental. The ellipticity to which they conform differs more consi- 

 derably than could have been expected, from 30 1. 15 , which had 

 been previously received on the authority of the most eminent 

 geometrician of the age, as the concurrent indication of the mea- 

 surements of terrestrial degrees, of pendulum experiments, and of 

 the lunar irregularities dependent on the oblateness of the earth, 

 In further attestation of the irreconcilability of the variation of gra- 

 vity now manifested, with the ellipticity inferred in the memoir in 

 which the Marquis de Laplace has discussed the results of previous 

 observation and experiment, it may be noticed that if each of the 

 tropical stations which I have visited be severally combined with 

 each of the stations within 45° of the pole, no one result, amidst all 

 the irregularities of local attraction, will be found to indicate so 

 small a compression as that of previous reception." 



Taking 39*1391 for the mean length of the pendulum in London, 

 latitude 51° 31' 8"*4, Captain Sabine observes, that it might pro- 

 bably vary almost the two-hundredth of an inch above or below 

 this length in different points of the same parallel of latitude, and on 



