10 MOLECULAR MOTION AND ITS ENERGY 5 



novelty and their entire variation from the ideas till then 

 y current . The mathematical theory which Clausius founded 

 on this hypothesis, and published in the memoir cited, as 

 well as in later papers, especially attracted attention, and 

 many physicists were induced by these investigations to 

 help in developing the theory and putting it to experimental 

 proof. 



It was, indeed, quickly found that these views on the 

 nature of gases were not new, but had been published very 

 often before Clausius, and indeed with perfect clearness 

 very long before. Clausius himself mentioned in his first 

 memoir a paper published by Joule 1 in 1851, which had 

 remained almost quite unnoticed, wherein the question is 

 taken up and treated in essentially the same way ; and 

 Joule refers to a paper by Herapath 2 which appeared in 

 1821. In 1845 there was also presented to the Koyal 

 Society of London a paper by Wat erst on, 3 which proceeds 

 on the same lines regarding molecular motion, but, for 

 /certain faults, was not printed till Lord Kayleigh pub- 

 lished it on account of its historical interest. 



A whole series of writers have further been named who 

 are said to have held and published similar views and to 

 have expressed them with more or less clearness ; this list, 

 beginning with the philosophers of classical antiquity, 

 runs through the Middle Ages to the last century. Of all 

 these writers, however, there is but a single one of conse- 

 quence from the present state of the theory, viz. Daniel 

 Bernoulli, 4 whose memory Franz Neumann has pre- 

 served for his pupils and posterity, and to whom P. du 

 Bois-Reymond 5 has directed the attention of his con- 

 temporaries by a German translation of a fragment of his 



1857, p. 353 ; Abhandlzvngen ilber die mechanised Warmetheorie, Brunswick 

 1867, 2nd part, p. 229 ; transl. Phil. Mag. [4] xiv. 1857, p. 108. 



1 Memoirs of the Manchester Lit. and Phil. Soc. [2] ix. 1851, p. 107; 

 reprinted later PMl. Mag. [4] xiv. 1857, p. 211. 



2 Annals of Philosophy [2] i. 1821, pp. 273, 340, 401. 



3 Phil. Trans, clxxxiii. 1892, p. 1. 



4 Hydrodynamica, Argentorati 1738, Sect. X. D. & J. Bernoulli, Nouv. 

 Princ. de Mec. et de Phys. &c. Eec. des pieces de prix, v. 1752. 



5 Pogg. Ann. cvii. 1859, p. 490. 



