274 THE OCEAN. [Book X. 



Thus, since the sun and earth rotate in the same 

 direction, as also do the revolving forces under con- 

 sideration in this section, therefore, according to the 

 foregoing, if the planes of their rotation coincided, 

 the radius of the moon's orbit round the earth point- 

 ing towards the sun would be shortened, and that 

 pointing in the opposite direction lengthened, so that 

 the line of the apsides would always point through 

 the earth and sun ; because its position, lying from 

 the point at which the revolving forces are in con- 

 junction to that in which they are in opposition, 

 would lead it through those bodies. 



5. But, the planes of rotation being inclined, the 

 sun's revolving force tends to throw the moon out of 

 the plane of the earth's rotation, and, as it leaves 

 that plane, the earth's revolvmg force decreases, allow- 

 ing the moon to fall towards the earth. This action 

 is reciprocal, and might attain its maximum in any 

 part of the orbit, being dependent on the changmg 

 of the inclination. 



Thus, instead of the moon's apogee and aphelion 

 coinciding and occurring when the moon was at its 

 greatest distance outside the orbit of the earth, as 

 would be the case if the revolving forces acted in the 

 same plane, they become dependent on the changing 

 of the intersection of the planes of rotation. By the 

 disturbing action of the changing inclination of these 

 planes, the perigee and perihelion might both be 

 thrown outside the orbit of the earth ; or the perigee 



