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than that produced in the combustion of nine wax candles, each 

 three-quarters of an inch in diameter, all burning together with 

 clear bright flames." 



" One horse would have been equal to the work performed, 

 though two were actually employed. Heat may thus be produced 

 merely by the strength of a horse, and in a case of necessity this 

 might be used in cooking victuals. But no circumstances could be 

 imagined in which this method of producing heat could be advan- 

 tageous, for more heat might be obtained by using the fodder ne- 

 cessary for the support of the horse, as fuel. 



" By meditating on the results of all these experiments, we are 

 naturally brought to that great question which has so often been 

 the subject of speculation among philosophers, namely, What is 

 heat? Is there such a thing as an igneous fluid? Is there any 

 thing that with propriety can be called caloric ? 



" We have seen that a very considerable quantity of heat may 

 be excited by the friction of two metallic surfaces, and given off in 

 a constant stream or flux in all directions, without interruption or 

 intermission, and without any signs of diminution or exhaustion. 

 In reasoning on this subject we must not forget that most remark- 

 able circumstance, that the source of the heat generated by friction 

 in these experiments appeared evidently to be inexhaustible. (The 

 italics are Eumford's.) It is hardly necessary to add, that any 

 thing which any insulated, body or system of bodies can continue 

 to furnish without limitation, cannot possibly be a material sub- 

 stance ; and it appears to me to be extremely difficult, if not quite 

 impossible, to form any distinct idea of any thing capable of being 

 excited and communicated in those experiments, except it be MO- 

 TION." 



No one can read the remarkably able and lucid paper from 

 which these extracts are taken, without being struck with the per- 

 fect distinctness with which the problem to be solved was pre- 

 sented, and the systematic and conclusive method of its treatment. 

 Bumford kept strictly within the limits of legitimate inquiry, which 



