THE STORY OF NINETEENTH-CENTURY SCIENCE 



on the supposition that heat, the heaviest imponderable, 

 predominated in the lower atmosphere, and that light, 

 electricity, and magnetism prevailed in successively 

 higher strata, And Lavoisier, the most philosophical 

 chemist of the century, retained heat and light on a par 

 with oxygen, hydrogen, iron, and the rest, in his list of 

 elementary substances. 



But just at the close of the century the confidence in 

 the status of the imponderables was rudely shaken in 

 the minds of philosophers by the revival of the old idea 

 of Fra Paolo and Bacon and Boyle, that heat, at any 

 rate, is not a material fluid, but merely a mode of mo- 

 tion or vibration among the particles of "ponderable" 

 matter. The new champion of the old doctrine as to 

 the nature of heat was a very distinguished philosopher 

 and diplomatist of the time, who, it may be worth re- 

 calling, was an American. He was a sadly expatriated 

 American, it is true, as his name, given all the official 

 appendages, will amply testify ; but he had been born 

 and reared in a Massachusetts village none the less, and 

 he seems always to have retained a kindly interest in 

 the land of his nativity, even though he lived abroad in 

 the service of other powers during all the later years of 

 his life, and was knighted by England, ennobled by Ba- 

 varia, and honored by the most distinguished scientific 

 bodies of Europe. The American, then, who cham- 

 pioned the vibratory theory of heat, in opposition to all 

 current opinion, in this closing era of the eighteenth 

 century, was Lieutenant-General Sir Benjamin Thomp- 

 son, Count Rumford, F. R. S. 



Rumford showed that heat may be produced in in- 

 definite quantities by friction of bodies that do not 

 themselves lose any appreciable matter in the process, 



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