COUNT RUMFORD 173 



'What is heat ? ' and answers in accordance with his observa- 

 tions: 'It cannot be a material substance.' For it came out of 

 a limited system of bodies, namely the piece of metal in the 

 trough of water, continuously, and so in unlimited amount; 

 none flowed in, yet it flowed away on all sides, with- 

 out the slightest sign of chemical change appearing, say 

 in the water. The piece of metal subjected to friction was 

 fully demonstrated to be an inexhaustible source of heat: 

 'It appears difficult, if not quite impossible for me,' then says 

 Rumford, 'to imagine heat to be anything else than that 

 which in this experiment was supplied continuously to the 

 piece of metal, as the heat appeared, namely motion.' This 

 conclusion was a new legacy to natural science. In view of 

 the mass of new material already accumulated, and easier to 

 deal with, it remained for more than forty years untouched 

 until a quite original mind again appeared as a true seeker 

 after truth, and attacked the matter anew: Julius Robert 

 Mayer. 'Heat as a mode of motion,'^ could, it is true, not 

 be announced upon a perfectly sure basis until sixty years 

 after Rumford's time, when the work of Clausius, and also 

 the earlier work of Carnot, had appeared. The fact that in 

 all the years after Rumford's experiments, his idea, founded 

 upon the observation of nature, did not prevent the general 

 retention of the idea of a special heat-stuff, shows how 

 rarely academic men of learning are seekers of the truth. 

 Only a few noticed the contradictions to reality in which they 

 were involved. Among the few searching and original 

 minds, we have Davy, who, in order to be sure of the matter, 

 caused ice to melt by means of friction, and this succeeded 

 although the capacity for heat of the resulting water was 

 almost twice as great as that of the ice. He also caused 

 wax to melt by friction produced by a clockwork in an 



1 The title of a collection of lectures addressed both to scientists and 

 lovers of nature, given by John Tyndall in 1863 at the Royal Institution 

 in London. 



