418 PROCEEDINGS OF THE AMERICAN ACADEMY 



in a scientific point of view, overshadowed by the grand experiment of 

 Rumford, made at Munich in 1798, when, in the process of boring 

 cannon, he converted, by the agency of what has been vaguely called 

 friction, mechanical power into heat, and on a scale sufficient to boil 

 two and one half gallons of water ; and saw, with his clear, scientific 

 vision, that nothing could have been excited or communicated by this 

 operation but some kind of motion. Less dazzling, but no less con- 

 clusive, was Davy's later experiment of melting ice by rubbing. But 

 the views of Rumford were in advance of the general scientific thought 

 of his day by more than a generation, and were finally forced upon 

 science by the long and masterly series of experiments made by Joule. 

 The rude data supplied by Rumford's experiment gave, in the hands 

 of Joule, an approximate value to the mechanical equivalent of heat ; 

 but our knowledge of the precise rate of exchange in the mutual con- 

 version of heat and power rests upon the repeated, varied, and elabo- 

 rate experiments of Joule himself. I will now let Mr. Tyndall speak 

 for Rumford. ' When,' he says, ' the history of the dynamical theoiy 

 of heat is written, the man who, in opposition to the scientific belief 

 of his time, could experiment, and reason upon experiment, as Kum- 

 ford did, . . . cannot be lightly passed over. Hardly anything more 

 powerful against the materiality of heat has been since adduced ; hardly 

 anything more conclusive in the way of establishing that heat is, what 

 Rumford considered it to be, Motion.' 



" On the mechanical theory of heat, as a foundation, has been erected 

 the grandest generalization of physical science, the Conservation of 

 Energy. The results of observation and calculation agree, whenever 

 a comparison is practicable, if the calculation is made upon the assump- 

 tion that the totality of energy in a system, potential as well as dy- 

 namical, is as unchangeable as the totality of matter. This sweeping 

 generalization includes and interprets Grove's exi^erimental demonstra- 

 tion of the correlation and convertibility of the different forms of en- 

 ergy, known under the familiar names of gravity, elasticity, light, heat, 

 electricity, magnetism, and chemical affinities. The conversion of heat 

 (which is supplied to an indefinite amount by the consumption of the 

 forests and the coal-beds) into ordinary mechanical energy or work, 

 is of the highest significance to the advancing civilization of the race ; 

 but heat cannot be transformed into work without the transformation 

 of a larger amount of heat of high temperature into heat of low tem- 

 perature. This passage of heat from hot to cold bodies, without doing 

 work, reinforced by the conduction and radiation of heat, creates the 

 tendency to what is now called the dissipation of heat. Tiiis is what 



