•^86 THE CANADIAN NATURALIST. [Vol. 



Vll. 



each has its use; only the strong courses, the corner-stones au<l 

 the salient parts, are noticed. It will be thus with the monument 

 of science. The details which have for their end to fill up gaps 

 will disappear in the great whole, of which we only need consider 

 the foundatioUj the principal lines, and the crowning: of the 

 edifice. 



Gentlemen, chemistry thus constituted, and physics, have be- 

 tween them necessary connections. Both the one and the other 

 investigate the properties of bodies, and it is evident that, so 

 far as the ponderable bodies are concerned. ^these properties must 

 be intimately connected with the constitution of matter. Hence 

 the atomic hypothesis which suffices for the interpretation of 

 chemical phenomena ousht also to be adapted to physical theor- 

 ies. This is the case. It is in the movements of atoms and of 

 molecules that we now seek, not only the source of the chemical 

 forces, but the cause of the physical modifications of matter, 

 changes of condition which it can undergo, phenomena of light, 

 of heat, of electricity, of which it is the support. 



Two French savans, Dulong and Petit, discovered some time 

 ago a very simple law which connects the weights of atoms witli 

 their specific heats. It is known that the quantities of hear 

 necessary to change by one degree the temperature of the unit, 

 of weight of bodies are very unequal. This is what we call 

 specific heat; but the quantities of heat which bring about in 

 simple bodies, taken under conditions in which they are rigorously 

 comparable, the same variations of temperatures, are equal, if 

 we apply these quantities of heat not to the unit of weight but 

 to the atomic weight; in other words, the atoms of these element- 

 ary bodies possess the s.mie specific heats, though their relative 

 weights are very unequal. 



But as to this heat which is thus communicated to them, and 

 which raises their temperature equally, what is in reality its mode 

 of action? It augments the intensity of their vibratory move- 

 ments. Physicists recognise heat as a mode of motion, and that 

 it comes under the cognisance of our perceptions by the vibra- 

 tions of atomic matter or ether; of ether, that fluid material 

 perfectly elastic, incoercible, imponderable, which fills all the 

 immensity of space and the depth of all bodies. It is in this 

 fluid that the stars describe tlieir orbits; in this fluid atoms 

 perform their movements and describe their trajectories. Thus 

 the ether, the radiant mcssenfrer of heat and lisht. conveys and 



