AND ITS SELF-CONSEKVATION. 173 



Thus earth and moon must acquire momentum each in 

 a curved direction. And the momentum of the moon, 

 consisting in so large a degree of velocity, will carry the 

 moon quite over so as, approximately, to reach the line 

 originally extending between earth and sun. 



Meanwhile the earth must have moved toward the 

 sun, but must, also, have been drawn aside from a 

 straight line joining its original position with the sun 

 by the force impressed upon it by the moon's mass. 

 Whence it must result that the earth will speedily reach 

 a point exactly between sun and moon. 



Just at this point, so far as the attraction between earth 

 and moon affects the earth, it will tend to draw the earth 

 away from the sun; or, in other words, it will tend to 

 diminish the earth's velocity toward the sun. On the 

 other hand, the moon will now be drawn in one direc- 

 tion by the combined attraction of both earth and sun. 

 Hence, its velocity must be increased at the same time 

 that it rapidly changes the direction of its motion. 



Again, the acquired momentum of the earth must 

 carry it still further aside from the original line joining 

 it with the sun; so that by the time the moon has come 

 to follow the new direction of the impressed forces, the 

 attraction between itself and the earth will tend to carry 

 it again beyond the earth in the opposite direction. 



But now, the powerful impulse it has received from 

 the combined action upon it of earth and sun, must 

 not only carry it past the earth, but must also direct its 

 movement along a path lying between earth and sun. 

 And yet, the increased intensity of gravitation between 

 earth and moon, from their nearer approach must result 

 in a rapid change of direction in the moon's motion, and 



