THE ATOMIC VIEW OF NATURE. 



433 



brought about by the development of the so-called kinetic 

 theory of gases in the second half of the century. This is 

 a physical, not a chemical, theory. 



The kinetic theory of gases, invented for the purpose 

 of explaining the pressure which all bodies in the gaseous 

 state exert on the walls of the containing vessels, will 

 always be identified with the two names of Clausius in 

 Germany and Clerk Maxwell in England. 1 But if we 



1 Before the atomic view of matter 

 had, in the course of the last fifty 

 years, closely and definitely allied 

 itself with the kinetic view, it had 

 been allied with the astronomical 

 view of matter. In the last cen- 

 tury and the earlier decades of 

 the present century we frequently 

 find the behaviour of a complex 

 of molecules or atoms compared 

 with that of a planetary system ; 

 but in addition to the forces of 

 attraction, those of repulsion had 

 to be resorted to in order to ex- 

 plain the expansiveness of gases. 

 Heat was then considered to be a 

 material substance, the particles of 

 which repelled each other. Dalton 

 favoured this view in the introduc- 

 tion to his 'New System of Chemical 

 Philosophy ' ; so did Berthollet and 

 most of the French physicists who 

 were brought up in the school of 

 Newton and Laplace. Lasswitz, in 

 his ' Geschichte der Atomistik ' (2 

 vols., Hamburg, 1890), has traced 

 the ' Decline of Kinetic Atomism ' in 

 the seventeenth century under the 

 influence of the ' Corpuscular Philo- 

 sophy.' The kinetic view of matter 

 was allied with the Cartesian physi- 

 cal philosophy, which was dispelled 

 by Newtonianism in France and by 

 Kant's philosophy in Germany. In 

 consequence, when in Germany A. 

 Kronig published his ' Grundziige 

 einer Theorie der Gase' in 1856, 

 philosophers who had been speculat- 

 ing in the direction of a Newtonian 



VOL. I. 



atomism (see Fechner's ' Atomen- 

 lehre,'1855 ; Redtenbacher's 'Dyna- 

 miden System,' 1857 ; and other 

 publications quoted by Rosenberger, 

 ' Geschichte der Physik,' vol. iii. p. 

 536, &c.) were much taken by sur- 

 prise. It had the immediate result 

 of inducing R. Clausius, who had 

 been occupied with similar re- 

 searches since 1850, to publish his 

 celebrated memoir, 'Ueber die Art 

 der Bewegung welche wir Warme 

 nennen ' (Poggendorf's ' Annalen,' 

 vol. c., 1857). These two publica- 

 tions first called general attention 

 to the subject. Joule's paper, 

 which appeared in the ' Memoirs of 

 the Lit. and Phil. Soc. of Man- 

 chester,' had remained unnoticed, 

 but was reprinted by him, at the 

 request of Clausius, in the ' Philoso- 

 phical Magazine ' (4th ser. vol. xiv.) 

 in 1857. Subsequently, the re- 

 searches of Paul du Bois-Reymond 

 and others unearthed a whole list 

 of authors who, in more or less 

 definite ways, had resorted to the 

 hypothesis of a rectilinear trans- 

 latory motion of the molecules in 

 order to explain the phenomena of 

 pressure and other properties of 

 gases. Among these, Daniel Ber- 

 noulli (in his ' Hydrodynamica,' 

 1738) seems to have expressed the 

 clearest views, and he is now usu- 

 ally named as the father of the 

 hypothesis. The fullest statement 

 of the historical data will be found 

 in the posthumous second edition of 



2 E 



