﻿282 Prof. J. Bay ma on the Fundamental 



ment that I conceive heat " to originate n in the vibrations of the 

 molecules of bodies is not equally correct. I said indeed that 

 " the first cause of calorific motion is to be found in the very 

 constitution of molecules .... which are always subject to vibra- 

 tory motion " (Molecular Mechanics, p. 264) : but the first 

 cause is only one out of many, as nothing is called first without 

 reference to a second. On the other hand, when speaking of 

 vibrativity, to which I trace the phenomena of heat, I state that 

 vibrativity, as a general property of bodies, implies the capability 

 of making vibrations determined u by an extrinsic agent " (Ibid. 

 p. 171). In fact, I conceive heat to consist, though not to origi- 

 nate, in certain vibrations of the molecules of bodies, and these 

 vibrations to depend first on the molecular constitution of bodies, 

 secondly on any extrinsic causality that is brought to bear on 

 their velocity and intensity. If Professor Norton proves " almost 

 to a demonstration " that this view is untenable, I shall be thank- 

 ful to learn in what his proof consists. Should he however, as 

 I am afraid he will, argue from the supposed existence and work- 

 ing of universal sether between the molecules of bodies, I would 

 tell him beforehand that such a proof, besides other considerable 

 objections, might admit of a reply drawn from the well-known 

 law of calorific capacities. 



Luminiferous ather. — One of my objections against Professor 

 Norton's theory was that luminiferous sether, according to him, 

 was a repulsive and resisting medium, which I had shown to be 

 irreconcilable with astronomical facts. He answers : 



" The principal astronomical fact here referred to is that the 

 planets do not encounter any sensible resistance in their motion 

 through space. The evidence of an sethereal resistance afforded by 

 Encke's comet, Professor Bayma strives to explain away without 

 success." 



I give to the reader the opportunity of judging for himself of 

 this point of our controversy, by transcribing the passage referred 

 to by the learned critic. " How do we know that Encke's comet 

 cannot possibly have suffered a change in its orbit, unless it 

 moves through a resisting medium ? Have we any evidence, or 

 even any ground whatever for a probable conjecture, that there 

 is absolutely nothing in interplanetary spaces, except the medium 

 and those bodies which we have hitherto observed? To dis- 

 courage such a supposition it would suffice to mention Le Ver- 

 rier's discovery. I do not say that we shall hereafter discover 

 any new celestial body by whose action to account for the modi- 

 fication of the orbit of Encke's comet : there are perhaps thou- 

 sands of bodies in the solar system of which we have no notion, 

 and never shall have, on account of their being unobservable. I 



