On the Action of certain Vapours on Films, 111 



closing surface, and the given condition that the surface passes 

 through A and B. 



The solid resulting from the foregoing investigation possesses 

 the characteristic of a maximum, and is the only solution which 

 the problem admits of. It is antecedently evident that the con- 

 ditions of the question must admit of being satisfied by a sur- 

 face of some kind passing through the given points, and that 

 consequently the calculus of variations could not fail to give such 

 a solution. 



Cambridge Observatory, 

 July 19, 1861. 



XVII. Oil the Action of certain Vapours on Films ; on the Mo- 

 tions of Creosote on the surface of Water, and other phenomena. 

 In a Letter addressed to W. A. Miller, Esq., M.D., F.R.S. 

 fyc, Professor of Chemistry, King's College, London. By 

 Charles Tomlinson, Lecturer on Science, King's College 

 School*. 



My dear Miller, 



A FEW days ago, after a lecture at College on Cohesion and 

 Adhesion, one of my pupils asked me, " What is the cause 

 of the remarkable agitation that takes place when sulphuric ether 

 is dropped on the surface of water? " I put that same question 

 to myself more than five and twenty years ago while studying 

 chemistry, and made a large number of experiments on the sub- 

 ject, some of which I have lately had the pleasure of showing you. 

 As you were kind enough to express great interest in them, and 

 a desire that I would complete the inquiry by pushing it to a 

 definite conclusion, I have endeavoured to do so, and will with 

 your permission submit the whole inquiry to you from my own 

 point of view. 



But in order to do this I must go back to the years 1837-38, 

 when I obtained a large number of results, and embodied them 

 in three Articles which are now before me in MS. I did not 

 publish them, because the conclusions were not quite satisfactory 

 to my own mind. But being engaged about that time in seeing 

 my ' Students 5 Manual of Natural Philosophy' through the press, 

 I included the principal experimental results in that work, where 

 you will find them at pages 545-549, and again at pages 553- 

 555. The popular nature of this work doubtless caused these 

 experiments to remain unknown to scientific men ; and I venture 

 to think that they will even now strike many with an air of novelty. 

 This is my excuse for a short summary of old results by way of 

 introduction to new ones, or, at least, to such as have not been 

 published. 



* Communicated by Dr. Miller. 



