ON THE PHYSICAL VIEW OF NATURE. 



125 



to be an axiom with them, but even this apparently 

 simple article of faitli in natural philosophy meant 

 somethini; diflerent to different thinkers accordin<: to 

 the greater or less clearness of their physical concep- 

 tions. Helmholtz, in his celebrated memoir of 1847, 

 conceives all natural processes to be ultimately re- 

 ducible to purely mechanical processes, and in doing 

 so he sees that a well-known law in mechanics, the 

 conservation of the vis viva, must have a meaning for 

 all natural forces. This he proceeds to develop. Others, 

 like Faraday, Mohr, Grove, have a silent conviction that 

 besides ponderable matter there is some other quantity 

 in nature which is indestructible and cannot be created, 

 but only changed and transferred ; they frequently call it 

 force, and thus entangle themselves or their readers in 



destroyed. Under the influence 

 of Oersted's pliilosophy Colding 

 expresses similar ideas in 1843 

 (see ' Phil. Mag.,' 4th series, vol. 

 xxvii. p. 58). In fact, during the 

 fifth decade of the century the 

 three conceptions of the impossi- 

 bility of creating power, its inde- 

 structibility, and the converti- 

 bility of its different forms, were 

 more and more clearly enunciated. 

 They were at last expressed in 

 the formula of the " conservation 

 of energy.'' It was Tiiomson (Lord 

 Kelvin) who then — in 1852 — first 

 clearly recognised that the old phan- 

 tom of a perpetual motion was 

 turning up again in a new form. 

 (See his Essay on " Dissijiation of 

 Energy " in the ' Fortnightly Re- 

 view,' March 1892, reprinted in 

 ' Popular Lectures and Addresses,' 

 vol. ii. p. 452.) Ever since Thom- 

 son's essay of 1852 naturalists 

 and philosophers may be said to 

 be tj-ying to formulate in the 

 simplest terms the great [)i'inciple 



of nature, that though energy is 

 never lost, it becomes — for our 

 practical purposes — unavailable. 

 Prof. Ostwald has expressed this 

 by reviving the terminology of 

 the perpetual motion. " It is not 

 generally recognised that the 

 principle of perpetual motion has 

 two sides. On the one side . . . 

 perpetual motion could be realised 

 if one could create energy. . . . 

 The expression of the impossi- 

 bility of doing this is the first law 

 of Energetics. ... A perpetual 

 motion could, however, on the 

 other side be attained if it were 

 possible to induce the large store 

 of energy at rest to enter into 

 transformations. . . . This might 

 be termed a perpetual motion of 

 the second kind." The impossi- 

 bility of this Ostwald terms the 

 second princi|)le of Energetics 

 ('Allgemeine Cliemie,' vol. ii. 

 part 1, p. 172 ; cf. Helm, 

 'Energetik,' p. 304). 



