ON THE PHYSICAL VIEW OF NATURE. 



125 



to be an axiom with them, but even this apparently 

 simple article of faith in natural philosophy meant 

 something different to different thinkers according 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 philosophy 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 Thomson (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 " Dissipation 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 trying to formulate in the 

 simplest terms the great principle 



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 principle of Energetics 

 (' Allgemeine Chemie,' vol. ii. 

 part 1, p. 472; cf. Helm, 

 'Energetik,' p. 304). 



