GRAVITATION VERSUS INERTIA 19 



projectile character of the motion itself. The possi- 

 bility that thcie never ic>as sucft on original motion, but 

 that th* 3 planets are being actuated by some presently 

 acting force as powerful and invisible as the centripetal 

 force it*eU. seems never to have been considered. 



Assuming this initial motion (which is indifferently 

 called "momenta!," "projectile," or "inertial" ) divine- 

 ly imparted, according to Newton ; spontaneous, accord- 

 ing to science the problem still remained how to skimp 

 along with it forever; FOR, BY EXPRESS PROVISO, IT CAN 



NEVER RECEIVE AUGMENTATION, AND MUST THEREFORE BE 

 THEORETICALLY HUSBANDED AGAINST ALL POSSIBILITY OF 

 WASTING. 



The first difficulty that had to be cogitated out of 

 the way was that of a resisting medium (atmosphere) 

 in space, for did such a medium exist its inevitable effect 

 would be, or rather must already have been, to wear 

 down the moon's alleged momentum and precipitate it 

 upon the earth. It has been proved beyond dispute, 

 from ancient records of eclipses, that the moon is not 

 only not slowing up, but is actually traveling faster and 

 faster as the centuries fly by (10" of arc in a century), 

 showing the theoretical necessity for either an ab- 

 solutely void space, or an absolutely imponderable 

 ether. Now, scientifically speaking, space dare not be 

 predicated as void, because light travels through it, 

 which it could not do without its stepping stones, atoms. 

 Hence it is seen that the theory of inertial motions 

 not only starts with their purely speculative origin and 

 existence, but is driven precipitately to build on that 

 aerial nothingness by affirming (no longer merely pos- 

 tulating) the tertium quid of a matter without sub- 

 stance, a something that is and at the same time is 

 not a threadbare sophistical device worthy only of the 

 Middle Aes. 



