﻿Principles of Molecular Physics. 279 



tivc answer from him. Unluckily he did not give one : at least, 

 I look in vain for it. In its stead he gives some short com- 

 ments upon the differences which I admit to subsist between 

 what he wrongly calls my f< two attractive forms of matter," and 

 especially upon my opinion on the density of luminiferous aether. 

 Yet the point at issue was not whether I have succeeded or not 

 in establishing the great density of luminiferous aether, but how 

 it can be proved that two aethers both repulsive must be ad- 

 mitted in nature. 

 He then says : 



" 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 aether. The evidence of their similarity is 

 much greater than of their dissimilarity." 



Why should we admit them ? The answer is plain. We 

 should admit the " repulsive envelope/' because we have proved 

 its existence as an essential part of the molecule (Molecular Me- 

 chanics, p. 147) : and we should admit an "attractive luminife- 

 rous aether," because we have also proved its existence by the 

 consideration of natural facts (Ibid. pp. 176-180). Had Pro- 

 fessor Norton done the same with regard to his three forms of 

 matter, I should never have thought of putting him the ques- 

 tion Why should we admit them ? 



From this answer the author will perceive that it is not pre- 

 cisely or solely in order to explain electric and optical phenomena, 

 but in order to account for all other phenomena, that the repul- 

 sive envelope of molecules and the attractive luminiferous aether 

 are to be admitted. The repulsive envelope however does not 

 deserve the name of a special substance; for it has not an inde- 

 pendent and complete constitution of its own, and belongs as a 

 constituent part to the molecule of which it is the envelope. 



As to the evidence of its similarity to luminiferous aether, 

 where is it ? 



The learned Professor concludes his answer by these words: 



" The only apparent force in the question under consideration is 

 derived from the fact that a vague conjecture is apt to be raised hy 

 it, that a single aether may be equal to all the duty now assigned to 

 both." 



Be it as he wills. Yet even a vague conjecture would have 

 no little weight against an assertion which, as we have shown, is 

 itself at the best only another vague conjecture. 



What Professor Norton adds immediately after has no need of 

 special reply. He says that my molecular envelope u is com- 

 posed of electric matter," and that the universal aether condensed, 



