M. Arago's Historical Eloge of Joseph Fourier, 223 



to the Academy, " The question which you have proposed only 

 interests the curiosity of mankind." 



Among the competitors who were less favourably treated, we 

 find one of the greatest writers whom France has produced, the 

 author of the Henriade. Voltaire's memoir was, undoubtedly, 

 far from solving the proposed problem, but it was at least re- 

 markable for the elegance, the clearness, and the precision of 

 its language ; I may add also, for the close reasoning it dis- 

 plays ; for, if the author occasionally arrives at doubtful results, 

 it is only when he borrows faJse data from the chemistry and 

 natural philosophy of the time, — sciences which were then in 

 their infancy. Besides, the anii-cartesian nature of some articles 

 in Voltaire's memoir, was likely to find little favour in an assem- 

 bly where Cartesianism, with its incomprehensible vortices^ was 

 in full vogue. 



It would be more difficult to discover the causes which led 

 to the rejection of the memoir by the Marchioness du Chdtelet^ 

 for she had also entered the lists of the Academy. Her work 

 was not only an elegant account of all the properties of heat at 

 that time known to natural philosophers ; but it was also re- 

 markable for various proposals for experiments, one, among 

 others, which was afterwards followed up by Herschel, and 

 from which he derived one of the chief gems in his brilliant 

 scientific crown. 



Whilst these great names were engaged in this competition, 

 natural philosophers who were less ambitious, laid, experimen- 

 tally, the solid foundations of a future mathematical theory of 

 heat. Some proved that the same quantities of caloric do not 

 raise, by an equal number of degrees, the temperature of equal 

 weights of different substances, and thus added to science 

 the important idea of capacity. Others, by means of observa- 

 tions not less certain, proved, that heat applied at one point of 

 a bar, is transmitted to the distant parts with more or less 

 quickness or intensity, according to the nature of the substance 

 of which the bar is composed : thus they gave rise to the first 

 ideas of conductibility. The same period, if I could enter into 

 . detail, would exhibit to us interesting experiments, on a law of 

 cooling, hypothetically admitted by Newton. We should see 

 that it is not true, that, at all point? of the thermometer, the 



