ON THE INTERACTION OF NATURAL FORCES. 149 



might be easily and completely stated. It was found that all 

 known relations of forces harmonise with the consequences of 

 that assumption, and a series of unknown relations were dis- 

 covered at the same time, the correctness of 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 conclusions, his ex- 

 periment was not quite unsuccessful. He discovered a law which 

 now bears his name, and to which I will return further on. 



His labours 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 pre- 

 sented a memoir to the Academy of Copenhagen, in which the 

 same law found utterance, 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.' 1 



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

 New Series, p. 114. J. T. 



