Reflections on Heat. 173 



that it is by the very rapid vibrations which take place 

 in these atmospheres that those undulations in the sur- 

 rounding ether are excited by means of which the tem- 

 perature of objects is altered. 



The adoption of this latter hypothesis will reconcile, 

 to a certain extent, the theory of vibrations with that 

 of a calorific substance; but still the heating of a body 

 cannot be regarded, in any respect, as the result of the 

 accumulation of this substance, but as the acceleration 

 of its motion. 



In order to establish on a firm foundation the theory 

 of heat which is based upon the vibratory hypothesis, 

 it is necessary not only to show that the vibrations in 

 question are possible, but also to prove that the undu- 

 lations which they should cause do really exist. 



In the ordinary condition of things, the objects which 

 surround us do not afford any indication of radiation, 

 nor do they produce any effect capable of manifesting 

 itself to any one of our senses in such a way as to lead 

 us to suspect that they possess radiating surfaces. But 

 the philosopher who aims at penetrating into the mys- 

 teries of Nature must be continually on his guard that 

 he may not be deceived either by the testimony or by 

 the silence of his senses. 



In the first place it is evident that our various organs 

 were formed with reference to the daily wants of life ; 

 and that, if they were too sensitive, the pleasure which 

 they afford us would be turned into actual pain. 



If our ears had been constructed so as to be sensibly 

 affected by all the vibrations which take place in the 

 air, we should, without doubt, be stunned by the 

 intolerable noise, even in the deepest retirement ; and 

 if our eyes took cognizance of all the rays that strike 



