170 SCIENTIFIC THOUGHT. 



the universal tendency in nature towards a dissipation 

 of energy, by saying, "The entropy of the world is 

 always on the increase." 



For about twenty years after these conceptions had 

 been introduced into scientific language and reasoning, 

 mathematicians and physicists were mainly occupied 

 in denning more clearly this hidden quantity, and in 

 defending what was called the second law of thermo- 

 dynamics against misconceptions and attacks. In 1875 

 Lord Kayleigh could still say, 1 " The second law of thermo- 

 dynamics and the theory of dissipation founded upon it 

 has been for some years a favourite subject with mathe- 

 matical physicists, but has not hitherto received full 

 recognition from engineers and chemists, nor from the 

 scientific public. And yet the question under what 

 circumstances it is possible to obtain work from heat 

 is of the first importance. Merely to know that when 

 work is done by means of heat, a so-called equivalent of 

 heat disappears, is a very small part of what it concerns 

 us to recognise." 



"Whilst these words correctly describe the general 



attitude of the scientific public towards this important 



discovery, two men had already made a beginning in 



Horstmann. the direction indicated Horstmann 2 in Germany, and 



1 ' Proceedings of the Royal In- which began in the year 1869 and 



stitution,' vol. vii. p. 386. were continued in Liebig's ' An- 



- Prof. Ostwald in the historical ! nalen ' in various communications 



section of his ' Verwandtschafts- during the early 'seventies, not 



lehre' ('Allg. Chemie,' 2nd ed., ' without undergoing violent attacks 



vol. ii. part 2, p. Ill, &c.), Helm from representatives of the older 



in 'Euergetik' (p. 141, &c.), and ' conceptions. Ever since James 



Duhem in his ' Traite de Mecanique Thomson's celebrated prediction 



chimique' (1897,*'ol. L p. 84, &c.) (see above, p. 126), physicists 



all do full justice to the long-un- had recognised the importance of 



recognised labours of Horstmann, thermo dynamical considerations, 



