224 INTERACTION OF NATURAL FOKCES. 



which remained to be proved. If a single one of them could 

 be proved false, then a perpetual motion would be possible. 



The first who endeavoured to travel this way was a French- 

 man, named Carnot, in the year 1824. In spite of a too 

 limited conception of his subject, and an incorrect view as to 

 the nature of heat, which led him to some erroneous conclu- 

 sions, his experiment was not quite unsuccessful. He dis- 

 covered a law which now bears his name, and to which I will 

 return further on. 



His labors remained for a long time without notice, and it 

 was not till eighteen years afterwards, that is, in 1842, that 

 different investigators in different countries, and independent 

 of Carnot, laid hold of the same thought. 



The first who saw truly the general law here referred to, 

 and expressed it correctly, was a German physician, J. R. 

 Mayer, of Heilbronn, in the year 1842. A little later, in 

 1843, a Dane, named Colding, presented a memoir to the 

 Academy of Copenhagen, in which the same law found utter- 

 ance, and some experiments were described for its further 

 corroboration. In England, Joule began about the same time 

 to make experiments having reference to the same subject. 

 "We often find, in the case of questions to the solution of 

 which the development of science points, that several heads, 

 quite independent of each other, generate exactly the same 

 series of reflections. 



I myself, without being acquainted with either Mayer or 

 Colding, and having first made the acquaintance of Joule's 

 experiments at the end of my investigation, followed the same 

 path. I endeavoured to ascertain all the relations between the 

 different natural processes, which followed from our regarding 

 them from the above point of 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. A great number of the 



