74 THE ADVANCE OF SCIENCE 



the part of a contemporary, of great ac- 

 quirements and remarkable intellectual 

 powers, to read the signs of the times, is 

 a lesson and a warning worthy of being 

 deeply pondered by anyone who attempts 

 to prognosticate the course of scientific 

 progress. 

 What I have pointed out that the growth of 



this doc- t t -i xi 'l i.- j_i 



trine is. clear and definite views respecting the 

 constitution of matter has led to the con- 

 clusion that, so far as natural agencies 



that vibrations of molecules, causing and caused by vi- 

 brations of the ether, constitute heat, is discussed. See 

 vol. ii. p. 587, 2nd ed. In the Philosophy of. the In- 

 ductive Sciences, 2nd ed., 1847, p. 239, Whewell re- 

 marks, a propos of Bacon's definition of heat, ' that it is 

 an expansive, restrained motion, modified in certain 

 ways, and exerted in the smaller particles of the body ; ' 

 that ' although the exact nature of heat is still an ob- 

 scure and controverted matter, the science of heat 

 now consists of many important truths ; and that to 

 none of these truths is there any approximation in 

 Bacon's essay.' In point of fact, Bacon's statement, 

 however much open to criticism, does contain a dis- 

 tinct approximation to the most important of all the 

 truths respecting heat which had been discovered when 

 Whewell wrote. 



