ON THE PHYSICAL VIEW OF NATURE. 105 



embrace a mechanical or kinetic view of the nature 

 of heat. Joule, as stated above, 1 was the first who 

 emancipated himself from it. 



But whilst these suggestions that heat may be re- s. 



Correlation 



garded as somehow connected with motion remained offerees, 

 mostly vague and undeveloped, they tended to impress 

 upon the scientific mind the interchangeability or, as 

 it was called, the correlation of the different forces of 

 nature ; and the idea seems to have forced itself in- 

 dependently on many minds, through the study of very 

 different groups of natural phenomena. In Germany 

 we may look upon Liebig as the centre of a great ,9. 

 scientific movement which tried by means of chemistry 

 to bring the realms of organic and animated exist- 

 ence under the treatment of exact methods. Not 

 only were the methods of organic analysis perfected 

 by him and his school, and many compounds inves- 

 tigated which appeared to be specially the bearers of 

 the living process ; but he was also among the first to 

 study the economy of living organisms, the circulation 

 of matter, and .the play of the varied processes by . 

 which life is maintained. Among these processes, the 

 phenomenon of animal heat, its origin, and the part it 

 plays in the living organism attracted special attention. 



may be said to rest where it did | which was shown to have the same 



at the time these Lectures were ! properties of reflexion, refraction, 



written. The facts which have | and polarisation as light possessed, 



just been mentioned clearly point ! The analogy of this form of heat 



out its undulatory character" (p. I with light threw into oblivion 



506). Between the years 1835 and j the beginnings of a more general 



1845 theoretical ideas on the nature j mechanical theory of heat, which 



of heat were entirely dominated j as we shall see further on had 



by the remarkable discoveries of ; been laid by Sadi Carnot in 



Melloni, Baden-Powell, Forbes, and ! 1824. 



others referring to radiant heat, I : See vol. i. of this work, p. 434. 



