PHYSICAL ASTRONOMY. 303 



From the quantity of this change of direction, the 

 ratio of the attraction of the mountain to the at- 

 traction of the whole Earth, or to the force of 

 gravity, was found to be that of 1 to 17804. 



The bulk and figure of the mountain being also given 

 from the survey, the mean density of the moun- 

 tain was found to be to the mean density of the 

 Earth nearly as 5 to 9. Phil. Trans, vol. LXVIII. 

 p. 781. Also HUTTON'S Tracts, vol. in. p. 62. 



The mean density of the Earth, is therefore nearly 

 double the density of the rocks which compose 

 Schehallien, which seem again to be considerably 

 more dense than the mean of those which form the 

 exterior crust of the Earth. Phil. Trans. 1811, 

 p. 347. 



306. If the density of the Earth increase 

 toward the centre, the elliptic! tj of the sphe- 

 roid, and the diminution of gravity from the 

 pole to the equator will not both be expressed 

 by the same fraction as in the case of the homo- 

 geneous spheroid, but the sum of the two frac- 

 tions will always be equal to the same quan- 

 tity, viz. - or .008695. 

 1 Lo 



This theorem was first given by CLAIRAUT, and is of 

 great use, as serving to explain the connection be- 

 tween the ellipticity, as ascertained from the mea- 

 surement 



