III. 



THE MECHANICAL EQUIVALENT OF HEAT. 



vast and magnificent structure of the experimental 

 _1_ sciences has been erected on only a few pillars. His- 

 tory teaches us that the searching spirit of man required 

 thousands of years for the discovery of the fundamental prin- 

 ciples of the sciences, on which the superstructure was then 

 raised in a comparatively short time. But these very funda- 

 mental propositions are nevertheless so clear and simple, that 

 the discovery of them reminds us, in more than one respect, 

 of Columbus's egg. 



But if, now that we are at last in possession of the truth, 

 we speak of a method by the application of which the most 

 essential fundamental laws might have been discovered with- 

 out waste of time, it is not that we would criticize in any light 

 spirit the efforts and achievements of our forerunners : it is 

 merely with the object of laying before the reader in an ad- 

 vantageous form one of the additions to our knowledge which 

 recent times have brought forth. 



The most important not to say the only rule for the 

 genuine investigation of nature is, to remain firm in the con- 

 viction that the problem before us is to learn to know phenom- 

 ena, before seeking for explanations or inquiring after higher 



