40 CIRCULATION OF THE AETHER. 



hilated, it must either accumulate in the planetary 

 spaces, and thus raise their mean temperature ; or 

 it must return to the great fountain from which it 

 emanates. It also follows, that if the vast aethe- 

 real tide flow perpetually toward the sun, with 

 the same force which it exerts in maintaining 

 the centrifugal power of planets, there is no good 

 reason why it should not be the cause of the cen- 

 tripetal force which maintains them in their 

 orbits ; consequently, that the projectile and gra- 

 vitating forces of Sir Isaac Newton are owing to 

 one and the same principle which produces all 

 the contractions and expansions, separations and 

 combinations of the particles of ponderable mat- 

 ter ; as will be proved in the third chapter of this, 

 and the whole of the second book. Nor can there 

 be a rational doubt, that in the total absence of 

 solar radiation, all the mechanical, chemical, and 

 vital operations of the planets would be arrested ; 

 and that if the interstellary spaces were reduced 



" the greatest part of the sun's attraction, which is common to 

 both, is exerted in retaining both primary and secondary in their 

 common orbit about himself, and in preventing them from part- 

 ing company ; the small excess of force acting only as a disturbing 

 power." And he states that, according to the calculations of 

 Newton, the mean value of this excess, in the case of the moon's 

 disturbance by the sun, does not exceed ^fo of the principal force 

 which retains the moon in its orbit. (Astronomy, sect. 493). It 

 must also diminish, relatively, as the magnitude and distance of 

 planets increase. Yet it is sufficient to give the orbits of their 

 satellites the character of somewhat zigzag circles. 



