Principles of Molecular Physics. 41 



and as constituting an especial claim to favourable regard, will 

 be likely to prove its sufficient condemnation. 



The entirely different stand-point occupied by Professor Bayma 

 from that which I have taken, and the consequent liability he 

 has incurred of misunderstanding my views, is the occasion of 

 much of the criticism he has indulged in. Thus he assails from 

 all points, and in a variety of modes, what he regards as one of 

 my strongholds, viz. that a primary atom has continuous exten- 

 sion and is spherical in form. Now, as a matter of fact, in fra- 

 ming my theory I took scarcely any thought of the question of 

 the continuity of matter in a primary atom. Conceiving the real 

 constitution of the atom to be incapable of detection, I simply 

 adopted the ordinary conception of it, recognizing in it the em- 

 bodiment of three essential truths, viz. (1) that the ultimate 

 element, called an atom, is incapable of division by either me- 

 chanical or chemical means, (2) that it acts with equal energy in 

 all directions, (3) that its surface opposes a repulsive resistance 

 to any other atoms that may be urged toward it by the attraction 

 of the whole atom. These three features cannot be conceived to 

 belong to a single point, but may either to a continuous material 

 sphere, or to a spherical collection of material points. It mat- 

 ters not, from my theoretical stand-point, which of these two 

 views be taken. 



But I have since been led (see my answer to Professor Bayma's 

 criticisms in the Philosophical Magazine, February 1869, p. 106) 

 to adopt the fundamental conception that the effective attraction 

 of a primary atom of ordinary matter for the luminiferous sether 

 probably consists in a diminished repulsion. Upon this view 

 the question of the size and constitution of primary atoms can 

 have no value in physical science, and may be left for the enter- 

 tainment k of those who have a predilection for metaphysical spe- 

 culations. 



Before taking up briefly some of the specific points discussed 

 in Professor Bayma's paper, it may be well to say a word in reply 

 to his affirmation that " hypothesis begins only where real science 

 ends." I would ask our learned author if real science had come 

 to an end when Newton conceived the hypothesis of universal 

 gravitation and followed it out to its legitimate consequences — 

 or when Huyghens imagined the existence of luminiferous sether 

 waves, and so laid the foundation of the undulatory theory of 

 light. 



Yale College, U.S., 

 June 1, 1869. 



[To be continued.] 



