416 JOSEPH FOURIER, 



causes of the failure of a fourth competitor, Madame the 

 Marchioness du Chatelet, for she also entered into the con- 

 test instituted by the Academy. The work of Emilia was 

 not only an elegant portrait of all the properties of heat, 

 known then to physical inquirers, there were remarked 

 moreover in it, different projects of experiments, among 

 the rest one which Herschel has since developed, and 

 from which he has derived one of the principal flowers 

 of his brilliant scientific crown. 



While such great names were occupied in discussing 

 this question, physical inquirers of a less ambitious stamp 

 laid experimentally the solid basis of a future mathemat- 

 ical theory of heat. Some established, that the same 

 quantity of caloric does not elevate by the same number 

 of degrees equal weights of different substances, and there- 

 by introduced into the science the important notion of ca- 

 pacity. Others, by the aid of observations no less certain, 

 proved that heat, applied at the 'extremity of a bar, is 

 transmitted to the extreme parts with greater or less 

 velocity or intensity, according to the nature of the sub- 

 stance of which the bar is composed ; thus they suggested 

 the original idea of conductibility. The same epoch, if I 

 were not precluded from entering into too minute details, 

 would present to us interesting experiments. We should 

 find that it is not true that, at all degrees of the thermom- 

 eter, the loss of heat of a body is proportional to the 

 excess of its temperature above that of the medium in 

 which it is plunged ; but I have been desirous of show- 

 ing you geometry penetrating, timidly at first, into ques- 

 tions of the propagation of heat, and depositing there the 

 first germs of its fertile methods. 



It is to Lambert of Mulhouse, that we owe this first 

 step. This ingenious geometer had proposed a very 



