MATERIALITY OF HEAT. 1 9 



having become so general, that it does not appear to have 

 occurred to any philosopher, before this time, that the 

 mechanical effect which the mechanical action of overcoming 

 friction (annihilating mechanical power) imparted to the 

 bodies, could in itself be the very imponderable fluid, 

 measurable, indestructible, and uncreatable, that constituted 

 caloric. That such a simple reconciliation, as it now appears, 

 should have been overlooked by both schools, receives its 

 explanation in the fact, already mentioned, that in the schools 

 of mechanical philosophy, "Work," the only general measure 

 of the mechanical effect transmitted during mechanical 

 action, had not been recognized ; so that those who realized 

 that heat was the result of mechanical action were yet 

 unaware that the action represented a transmission to the 

 heated body of a measurable amount of mechanical effect, 

 and thus failed to look to the measure of this effect as 

 affording a measure of the heat produced. 



Rumford came very near to revealing the true nature of 

 the relation between heat and mechanical effect by observing 

 that two horses working steadily against a frictional resist- 

 ance produced heat at a steady rate ; but although he 

 measured the quantity of heat produced, and even went so 

 far as to compare this with the heat that would have 

 resulted from the combustion of the food consumed by 

 the horses, he did not attempt any discussion of the 

 mechanical action involved. So that until ' work ' was 

 recognized in the schools as the measure of mechanical 

 potency, the description of his investigation did not 

 apparently contain a logical account of the relation between 

 heat and mechanical action, however fully Rumford himself 

 may have realized such a relation. 



The condensing steam engine had been at work for 150 



