Caloric by Friction. 369 



ing thus maintained at greater or less distances, in virtue of the 

 reciprocal actions of heat and the power of aggregation, they 

 must be separated from each other by interstitial spaces in which 

 all the phenomena of light, heat, mutual affinities, and atomic 

 attraction play their parts. It is then in these spaces that the im- 

 ponderable agents unceasingly contend with the material prin- 

 ciples of bodies. 



Caloric must here exert a very powerful agency ; for, accord- 

 ing to its intensity and mode of action, it produces both light 

 and electricity, and induces the play of the chemical affinities. 

 Hence it follows that we cannot study too minutely the proper- 

 ties of this agent in relation to the particles of bodies, if we wish 

 to ascertain its immediate influence in all that concerns natural 

 phenomena of the very highest order. These considerations 

 suggested the idea of a series of experimental researches which 

 have led to some new results, of which we shall now endeavour 

 to supply a sketch, entering as slightly as possible into those 

 technical details which it would be difficult to follow in a hasty 

 perusal. 



We shall first direct our attention to a body in equilibrium, 

 as it regards temperature, with the surrounding medium. If, in 

 any way, we so disturb this body, that its atoms lose their na- 

 tural equilibrium, it is evident that all the imponderable agents 

 which are placed in the interstitial spaces will be put in motion. 

 A crowd of phenomena is the immediate consequence, which the 

 philosopher must endeavour to analyze with every help which 

 science puts at his disposal. We shall first direct our attention 

 to the effects produced by heat v/hen friction is the disturbing 

 cause employed. 



It is well known that when two bodies are rubbed against 

 each other, heat and electricity are disengaged. Are these ef- 

 fects, which are concomitant, also dependent upon each other ? 

 This we shall discuss by and by, and shall dwell now solely 

 upon the effects of the heat. 



All that we know concerning the production of heat by the 

 mutual friction of two bodies may be reduced to this : the two 

 bodies become hot, and the quantity of heat emitted is sometimes 

 such that it is sufficient to set combustible bodies on fire. Thus it 

 is, that a wheel turning rapidly on the axletree takes fire ; and 



