Mr. J. McCWan on the Solitary Wave. 553 



of crystalline form are the outward results of the form of the 

 molecule ; this has often been imagined to be the case, but 

 the kinetic theory proves it. It is hardly necessary to enu- 

 merate the paths of experimental and theoretical investiga- 

 tion opened by a kinetic theory of solids ; but it is obvious 

 that a kinetic theory of liquids requires to be seen to. 

 Melbourne, April 1891. 



LXIV. Note supplementary to a Paper on the Solitary Wave. 

 By J. McCowan, M.A., B.Sc* 



IN the concluding section of a paper " On the Solitary 

 Wave," printed in the July number of the Philosophical 

 Magazine, I offered a brief criticism of certain views of Sir 

 George Stokes, which are contained in a paper ' On the 

 Theory of Oscillatory Waves/ republished in the first volume 

 of his Collected Papers, on the possibility of a solitary wave 

 being propagated without change of form. He has, however, 

 privately called my attention to the fact that not only had he 

 himself seen the error of his former opinion, but had, in a 

 paper " On the Highest Wave of Uniform Propagation " (Proc. 

 Camb. Phil. Soc. vol. iv.), suggested a method by which the 

 solitary wave might be approximated to by a sort of trial and 

 error process, though he had not attempted the approxima- 

 tion itself, which would be laborious. He has also published 

 a note to this effect in the September number of the Philo- 

 sophical Magazine, which, however, I have only just seen, 

 owing to my absence from town during the summer recess. 

 I greatly regret that, in ignorance of his more recent paper, 

 I should have offered any criticism of Prof. Stokes's earlier 

 views, a criticism to which I was only led by the considera- 

 tion that it would be impossible to pass over in silence the 

 opinions of an authority of such eminence when they were in 

 conflict with the results of my paper. 



In his last (t Note on the Theory of the Solitary Wave/' 

 already referred to, Prof. Stokes has explained how he had 

 previously been led to a wrong conclusion, and this need not, 

 I think, call for any remark on my part; but he has further 

 offered certain objections to my criticism to which it is 

 necessary for me to reply to prevent misinterpretation of my 

 remarks, which were possibly too brief to be quite free from 

 ambiguity. I refer to the third paragraph of the " Note." 

 He begins by saying that he cannot agree with me that the 

 expansion which he used is inadmissible. With respect to 



* Communicated by the Author. 



