454 Professor Tyndall on Count Bumford. [May 3, 10, and 17. 



could be imagined in which this method of procuring heat would be 

 advantageous; for more heat might be obtained by using the fodder 

 necessary for the support of a horse as fuel.' " 



This is an extremely significant passage, intimating, as it does, 

 that Rumford saw clearly that the force of animals was derived from 

 the food, no creation of force taking place in the animal body. 



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

 naturally," he says, " brought to the great question which has so often 

 been the subject of speculation among philosophers, namely, What is 

 heat — is there any such thing as an igneous fluid ? Is there anything 

 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 sigus of diminution or exhaustion. In 



reasoning on this subject, we must not forget that most remarkable 



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



I these exj)eriments appeared evidently to be inexhaustible. It is 



' ^ hardly necessary to add that anything which any insulated body or 



system of bodies can continue to furnish without limitation cannot 



possibly be a material substance ; and it appears to me to be ex- 



f>^ tremely difficult, if not quite impossible, to form any distinct idea 



of anything capable of being excited and communicated in those 



experiments, except it be Motion." * 



* ' Heat a Mode of Motion,' Lecture II. 



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