

536 Chemical Notices : — M. Deville on the Dissociation of Water. 



constantly increase the area described per second, or r^ts. And 

 if this state of things continued for ever, it would seem that the 

 diurnal rotation must be drawn upon. But as the tidal effects 

 would decrease with the increasing distance of the moon, and so 

 the disturbing elevations themselves tend to disappear, and pro- 

 bably also to become less oblique, it is perhaps premature to assert 

 anything on this subject. Whether in the course of this process 

 there would be a loss of vis viva in the whole system more than 

 enough to account for the work done in pushing the moon away 

 from the centre, would be another question to be solved before 

 Professor Tyndall could draw upon this fund for some infinite- 

 simal supply of heat. 



If, then, the continual maintenance of the tides is incompa- 

 tible with the existence of internal friction without some external 

 renewing force, I conceive the natural and the only conclusion 

 would be, that the tidal fluctuations themselves must be dimi- 

 nishing, and that whether the rotation be also slackening or not. 

 But as I do not see my way to imagining any state of things in 

 which an ocean solicited by external bodies can be without tidal 

 motion, I confess I believe that there is no such incompatibility — 

 that the simple account of the matter is, that the moon's attrac- 

 tive force (which, acting on a world where the coefficient of fric- 

 tion happened to be less, would produce a greater oscillation) 

 spends itself partly on overcoming friction, and partly on produ- 

 cing a constant wave, but one less than is indicated by a theory 

 which neglects friction. I suppose that the sudden addition of 

 a satellite to a planet would get up a tide in spite of frictional 

 resistance. If so, its continual presence can keep it up. 



Kitlands, Dorking, 

 April 23, 1863. 



LXXI. Chemical Notices from Foreign Journals. 

 %E. Atkinson, Ph.D., F.C.S. 



[Continued from p. 219.] 



IT STE.-CLAIRE DEVILLE has made* the following 

 -fl- • observations on the phenomenon of the dissociation of 

 water. 



When even a rapid current of hydrogen is passed through a 

 porous tube and the emergent gas collected, it is found to con- 

 sist of pure air instead of hydrogen. Hence the hydrogen is 

 dispersed in the atmosphere, and the air is absorbed in the 

 inside of the porous tube in virtue of endosmose. 



If this porous tube is fitted, by means of perforated corks, 



* Comptes Rendus, February 2, 1863. 



