1G8 ON THE IXTERACTION OF NATURAL FORCES. 



view. My inquiry was made public in 1847, in a small 

 pamphlet bearing the title, ' On the Conservation of 

 Force.' ^ 



Since that time the interest of the scientific public for 

 this subject has gradually augmented, particularly in 

 England, of which I had an opportunity of convincing 

 myself during a visit last summer. A great number of 

 the essential consequences of the above manner of view- 

 ing the subject, the proof of which was wanting when the 

 first theoretic notions were published, have since been 

 confirmed by experiment, particularly by those of Joule ; 

 and during the last year the most eminent physicist of 

 France, Regnault, has adopted the new mode of regarding 

 the question, and by fresh investigations on the specific 

 heat of gases has contributed much to its support. For 

 some important consequences the experimental proof is 

 still wanting, but the number of confirmations is so pre- 

 dominant, that I have not deemed it premature to bring 

 the subject before even a non-scientific audience. 



How the question has been decided you may already 

 infer from what has been stated. In the series of natural 

 processes there is no circuit to be found, by which me- 

 chanical force can be gained without a corresponding 

 consumption. The perpetual motion remains impossible. 

 Our reflections, however, gain thereby a higher interest. 



We have thus far regarded the development of force 

 by natural processes, only in its relation to its usefulness 

 to man, as mechanical force. You now see that we have 

 arrived at a general law, which holds good wholly inde- 

 pendent of the application which man makes of natural 

 forces ; we must therefore make the expression of our law 

 correspond to this more general significance. It is in the 

 first place clear, that the work which, by any natural pro- 



' There is a translation of this important Essay in the Scientific Memoirs, 

 New Series, p. 114.— J. T. 



