366 NINETEENTH CENTURY. PT. m, 



crowding upon us in the last few years, such as the phono- 

 graph, the microphone, and the electric light, but it must 

 be remembered that these are not strictly new discoveries 

 in science, but applications of principles already discovered. 

 Though of surpassing interest, they must be studied in 

 detailed works, or find their place in a history of inventions. 

 The last fifty years have been essentially a period of the 

 application of scientific knowledge to practical life, and if. 

 any justification were needed of the study of pure science, 

 it may easily be found in the fact that our railways, our 

 telegraphs, our steamships, our manufactures, which have 

 done so much for the prosperity of England, are all the 

 results of scientific principles studied at first for their own 

 sake, and many of them apparently as far removed from the 

 affairs of daily life as the molecular theory of gases or the 

 ultra-gaseous state of matter. 



Chief Works consulted. Rumford's 'Essays,' vol. ii. 'Friction a 

 Source of Heat,' 1798; Davy's 'Works,' vol. ii. 'Essay on Heat 

 and Light ; ' Joule's ' Mechanical Equivalent of Heat ' ' Phil. Trans.,' 

 1850; Mayer's 'Forces of Inorganic Nature '' Phil. Mag.,' 1843; 

 Tyndall's 'Heat a Mode of Motion;' Watts's 'Diet, of Chemistry,' 

 art. 'Heat;' Clerk - Maxwell's 'Theory of Heat;' Encyclopaedia 

 Britannica,' 9th ed. art. 'Atoms;' Tail's 'Recent Advances in Physical 

 Science/ 



