54 ULTIMATE SCIENTIFIC IDEAS. 



which the negation is inconceivable, that in passing from 

 any one degree of magnitude to any other, all intermediate 

 degrees must be passed through. Or, in the case before us, 

 a body moving at velocity 4, cannot, by collision, be re- 

 duced to velocity 2, without passing through all velocities 

 between 4 and 2. But were Matter truly solid — were its 

 units absolutely incompressible and in absolute contact — 

 this " law of continuity," as it is called, would be broken in 

 every case of collision. For when, of two such units, one 

 moving at velocity 4 strikes another at rest, the striking- 

 unit must have its velocity 4 instantaneously reduced to ve- 

 locity 2 ; must pass from velocity 4 to velocity 2 without any 

 lapse of time, and without passing through intermediate 

 velocities; must be moving with velocities 4 and 2 at the 

 same instant, which is impossible. 



The supposition that Matter is absolutely solid being 

 untenable, there presents itself the Newtonian supposition, 

 that it consists of solid atoms not in contact but acting on 

 each other by attractive and repulsive forces, varying with 

 the distances. To assume this, however, merely shifts the 

 difficulty: the problem is simply transferred from the ag- 

 gregated masses of matter to these hypothetical atoms. For 

 granting that Matter, as we perceive it, is made up of such 

 dense extended units surrounded by atmospheres of force, 

 the question still arises — What is the constitution of these 

 units? AVe have no alternative but to regard each of them 

 as a small piece of matter. Looked at through a mental 

 microscope, each becomes a mass of substance such as we 

 have just been contemplating. Exactly the same inquiries 

 may be made respecting the parts of which each atom con- 

 sists ; while exactly the same difficulties stand in the way of 

 every answer. And manifestly, even were the hypothetical 

 atom assumed to consist of still minuter ones, the difficulty 

 would re-appear at the next step ; nor could it be got rid of 

 even by an infinite series of such assumptions. 



Boscovich's conception yet remains to us. Seeing that 



