^18 M. Arago's Historical Eloge of Joseph Fourier, 



all those ingenious and productive processes which secure their 

 prosperity. Did not an eloquent person affirm lately, within 

 these very walls, that the subject of heat was scarcely studied 

 before Fourier ; that this celebrated geometrician had himself 

 made more observations than all his predecessors put together ; 

 and that, after inventing a new science, he had almost perfected 

 it at once. 



At the risk of being much less interesting, the organ of the 

 Academy of Sciences must refrain from such bursts of enthu- 

 siasm. He ought to recollect that these eloges are not only in- 

 tended to celebrate the discoveries of academicians, but that 

 they are also designed to encourage humble merit ; and that a 

 philosopher who is neglected by his contemporaries, is often 

 cheered amid his toilsome labours by the thought that he will 

 obtain justice from posterity. In so far as that depends on us, 

 let us take care that a hope so natural and so just be not de- 

 ceived. Let us hold up to legitimate admiration those chosen 

 men whom nature has endowed with the valuable faculty of 

 grouping together innumerable isolated facts, and deducing 

 beautiful theories from them ; but do not let us forget that the 

 sickle of the reaper had cut down the stalks of corn before any 

 one could think of collecting them into sheaves. 



Under the subject of heat are included the natural pheno- 

 mena and those produced by art, two perfectly distinct forms, 

 which were separately investigated by Fourier. I shall adopt 

 the same division, commencing, however, the historical analysis, 

 which I am to lay before you, with radiant heat. 



Nobody can doubt that there is a physical diiFerence, well 

 .wortiay of being studied, between a ball of iron at the ordi- 

 nary temperature, which can be handled with impunity, and 

 a ball of iron of the same dimensions which has been strongly 

 heated in the furnace, and which one cannot approach without 

 the risk of being burned. This diiFerence, according to most 

 natural philosophers, arises from a certain quantity of an elastic 

 fluid which is imponderable, or at least which is regarded as 

 such, with which the second ball had entered into combination 

 during the process of heating. The fluid which, by combin- 

 ing with cold bodies, renders them hot, is known by the name 

 of heat or caloric. 



