Page:The Mathematical Principles of Natural Philosophy - 1729 - Volume 1.djvu/330

 then leat of all, and returns to the firt magnitude nearly, when the body arrives at the next node. But if the nodes are ituate at the octants after the quadratures, that is between C and A, D and B, it will appear from what was jut now hewn that in the paage of the body P from either node to the ninetieth degree from thence, the inclination of the plane is perpetually diminihed; then in the paage through the next 45 degrees. to the next quadrature. the inclination is increaed; and afterwards again, in its paage through another 45 degrees to the next node, it is diminihed. Therefore the inclination is more diminihed than increaed, and is therefore always le in the ubequent node than in the preceding one. And by a like reaoning, the inclination is more increaed than diminihed, when the nodes are in the other octants between A and D, B and C. The inclination therefore is the greatet of all when the nodes are in the yzygies. In their paage from the yzygies to the quadratures the inclination is diminihed at each appule of the body to the nodes; and becomes leat of all when the nodes are in the quadratures, and the body in the yzygies; then it increaes by the ame degrees by which it decreaed before; and when the nodes come to the next yzygies returns to its former magnitude.

Becaue when the nodes are in the quadratures the body P is perpetually attracted from the plane of its orbit; and becaue this attraction is made towards S in its paage from the node C through the conjunction A to the node D; and to the contrary part in its paage from the node D through the oppoition B to the node C;