262 Mr, Graham on the Heat of Friction. [Oct. 



tricity are caused by an accumulation, or a deficiency, of our 

 superficial heat. That the electric fluid is really superficial 

 heat, and convertible into sensible heat in the manner explained. 



Hence we never perceive any thing which we can call the 

 radiation of electricity. We never find, that one electrified 

 body communicates any of its electricity to another body at a 

 distance by this means. For it follows from the doctrines 

 illustrated, that should ever electricity (superficial heat) emanate 

 from bodies in this manner, it should be in the shape of radiant 

 heat. 



We scarcely need adduce instances, in which heat, in its 

 sensible form, does attend the accumulation of electricity. 

 When a powerful current of the electric fluid is concentrated, 

 by being passed along a thin wire, the wire is heated to a great 

 degree, so as to become strongly radiant. In this way, charcoal, 

 or any other body, may be kept in the voltaic arc in a state of 

 intense ignition. Here, from the great repulsive force that must 

 attend such an accumulation of superficial heat, which will be 

 much enhanced by the retardation of the passage of the fluid, 

 occasioned by the imperfect conducting power of the substance, 

 a large portion is expelled with the necessary velocity, and 

 becomes thereby sensible heat. According to this theory, elec- 

 trical light and heat are derived from the same source as the 

 heat of friction ; and in neither case is there any production or 

 actual generation of these principles. '^>i 



The simplicity of this theory is its chief recommendation. 

 That heat, possessed of a substantial existence, should be found 

 alone, uncombined with matter, and that this combination, of a 

 most elementary kind, should, at all times, be brought about by 

 the calorific principle impinging with force upon the material 

 body, are not hard postulates. Most material substances, how- 

 ever strong their affinities for each other, require peculiarly 

 favourable circumstances to enable these affinities to act, other- 

 wise the bodies appear to a certain extent repulsive of each 

 other. Moreover, when we attribute to the matter of heat 

 diffused over the surfaces of bodies, an attraction for these 

 substances which yet does not amount to the production of a 

 combination, we are but extending to heat properties which all 

 other material substances evince, in adhesion, capillary attrac- 

 tion, &c. 



It is hoped likewise, that the theory of superficial heat is not 

 chargeable with that barrenness and want of practical apphca- 

 tion, which generally characterize premature speculations upon 

 abstract subjects. The knowledge of the existence of such an 

 agent, of its influence in friction and electricity, and of its con- 

 vertibihty into sensible heat, affords a clue of no small import- 

 ance to guide us in our researches. Its application in galvanism, 

 we shall, perhaps, hereafter, have an opportunity of exhibiting. 



