﻿Principles of Molecular Physics. 103 



atoms of the other. Professor Bayma assumes equally great 

 differences to subsist between his two attractive forms of mat- 

 ter. He remarks, "the distinction of such a medium " (a me- 

 dium for the transmission of light) " from any ponderable sub- 

 stance is not an hypothesis, but a necessary inference drawn 

 from observed facts ; w and again, iC I do not see how such a 

 fact n (that light can pass undisturbed through air notwithstand- 

 ing the immense number of air-particles it encounters) "can be 

 accounted for if aether is not immensely denser than atmospheric 

 air." The reason for the conclusion is groundless ; but it is 

 the conclusion itself that we have here to notice. He adds, 

 " with this great density aether possesses also a very great sub- 

 tilty." 



I might also reply to Professor Bayma by asking him why we 

 should admit, in order to explain electric and optical phenomena, 

 two substances so distinct as the repulsive envelope of molecules 

 and the attractive luminiferous sether. The evidence of their 

 similarity is much greater than of their dissimilarity. 



In speaking of the two aethers as subtile, it was meant that a 

 large number of their atoms occupied the interstices between the 

 atoms of gross matter. It was also, of course, recognized that 

 the velocity of propagation of a wave is much greater through 

 either of the aethereal fluids than through a mass of ordinary 

 matter. The only apparent force in the question under consi- 

 deration is derived from the fact that a vague conjecture is apt 

 to be raised by it, that a single aether may be equal to all the 

 duty now assigned to both. 



To proceed with our quotations : 



What we have said on the constitution of molecules demonstrates 

 indeed the necessity of granting to each molecule of ponderable 

 matter a repulsive atmosphere, which we have called the molecular 

 envelope. But this envelope is not of aether, since aether is not 

 repulsive. 



That is, is not of the same substance as his luminiferous aether, 

 which he regards as attractive. But the " atmosphere " which 

 corresponds in its direct operation with Professor Bayma's 

 "molecular envelope" is composed of electric matter, and this 

 is repulsive. It is true that I conceive the interstitial spaces of 

 this electric matter and the space between it and the central 

 atom to be pervaded by the aether of space ; but the mechanical 

 part chiefly played by this condensed universal aether consists in 

 its being the medium in which pulses are originated that con- 

 stitute the force of heat -repulsion. 



Had Professor Norton known the impossibility of continuous mat- 

 ter, he would have found out that what he calls an atom of gross 



