324 On the Precession of the Equinoxes, 



dent, that whatever be the size of the ring, equal portions 

 of it are on each side of the Ecliptick ; that is, the centre 

 of attraction passes through the centre of the matter of the 

 Earth and its ring ; so that all the effect, which the attrac- 

 tion of the Sun can have, in consequence of the ring, ari- 

 ses merely from the different distances of A and O equal 

 to the diameter of the Earth ; and such an effect as this, if 

 it is any sensible effect, it can have only at the solstices ; 

 for, at the Equinoxes, the portions of the ring on each side 

 of the Ecliptick are at equal distances from the Sun ; and of 

 course, from the solstices to the Equinoxes the effect, if 

 any milst be constantly diminishing. But while the Moon, 

 by reason of the angle of its orbit, is at a distance from the 

 plane of the Ecliptick on one side, there is nothing on the 

 other side to balance it, or to prevent it from being has- 

 tened, by attraction, to the plane. In fig. 2, pi. 3, letLPbea 

 portion of the moon's orbit, M the moon, and S E the 

 plane of the Ecliptick. It is evident, that when the Moon 

 is at L, there is nothing at P to balance it. 



Again, suppose the orbit of the moon was a ring of moons, 

 or any material substance, the case would be different from 

 that of the Equatorial ring, because the greater difference 

 in the distances of the different parts of the ring would 

 more materially affect the ratios of gravitation. 



The precession of the Equinoxes, if caused by the Equa- 

 torial ring, must arise, either from a diminution of the an- 

 gle of the Equator with the Ecliptick, or from a change in 

 the direction of the line of the Equatorial Nodes. 



As to the former, we have no evidence, that there is 

 such a regular diminution of the angle ; but on the contra- 

 ry, we knotv that a diminution of the angle, sufficient to 

 produce the annual precession of the Equinoxes, would 

 have made a sensible effect upon the seasons. 



With regard to the latter it is difficult, if not impossible 

 to see any method in which a regular and successive varia- 

 tion of the line of the nodes should be effected. In rela- 

 tion to the moon, we can see no rational method of ac- 

 counting for the entire revolution of its nodes, except the 

 eccentricity of its orbit. If the Earth was in the centre of 

 the moon's orbit, there would still be a motion of the nodes 

 backwardand forward, but no revolution. The centre of the 

 Equatorial ring is the centre of revolution and attraction, 

 ai'd we know net how a revolution of the Equatorial Nodes 

 could be effected. 



