AND THEORY OF THE HEAVENS. 121 



pensates for the deficiency of the parts which are placed 

 beyond the distance of any point situated in the planet 

 and which contribute nothing by their attraction to its 

 gravity. 1 When this superior density of the deepest matter 

 is very great, in virtue of the laws of attraction it trans- 

 forms the gravity that diminishes in the interior towards 

 the centre into an almost uniform force and brings the 

 ratio of the diameters nearer to that given by Huygens, 

 which is always the half of the ratio of the centrifugal 

 force to the gravity. Consequently, as these were to each 

 other as 2:3, the difference of the diameters of this planet 

 will not be J but of the equatorial diameter. And, 

 finally, this difference is further concealed by the fact that 

 Saturn, whose axis is always at an angle of 31 degrees to 

 the plane of its path, never presents its position exactly in 

 the direction of its equator as Jupiter does ; and this 

 diminishes the difference in its appearance almost by J. In 

 these circumstances, and especially at the great distance 

 of this planet, it is easy to see that the flattened form of 

 its body will not be so easily discernible by the eye as 

 might be thought. Nevertheless astronomy, whose progress 

 mainly depends upon the perfection of its instruments, will 

 yet perhaps, if I do not flatter myself too much, be put 

 by their aid into a position of reaching the observation 

 of such a remarkable property. 



What I have been saying about the figure of Saturn may 



1 For, according to Newton's Laws of Attraction, a body which 

 is situated in the interior of a ball is attracted only by that part 

 of it which is comprised in a sphere described round it at its 

 distance from the centre. The concentric part situated beyond that 

 distance, on account of the equilibrium of its attractions which annul 

 each other, does nothing to move the body either to the centre or 

 awav from it. 



