Chap. XXL] THE HEAVENS. 269 



would there form in the space beyond them a fresh 

 accession of gravitation acting towards the earth. 



But by the decrease of this direct force and con- 

 comitant increase of the astral force, the opposing 

 forces must again at some greater distance be brought 

 into equilibrium. 



The second normal line of equilibrium would be 

 disturbed in the same manner as the first by the 

 revolving force ; and bodies in it would be carried 

 farther from the earth by the astral force, until by 

 the force drawing towards the earth decreasing as 

 the square, and the revolving force decreasing as the 

 cube of the distance increased (as shown in Propo- 

 sition XXXII. of the first line of equilibrium), the 

 equilibrium of the opposing forces would be restored. 



Thus an indefinite number of successive lines of 

 equilibrium might be formed at different distances 

 from the earth. 



PEOPOSITION XXXIV. 



Theorem. — The distance within which the revolving- 

 force of the earth's gravitation will be effective in 

 causing surroundmg bodies in space to revolve 

 around the earth depends on the proximity and 

 relative power of other revolving forces. 



Because it is evident that, in the absence of any 

 other revolving force, that of the earth would extend 



