1 Mr. J. JefFreys's Experiments on Exosmose laith reference 



nished the same combinations as the ethylic formiate, as in- 

 deed would be foreseen by theory. 



Chloropyromucic sether appears to contain, according to the 

 last experiments of M. Malaguti, ethylic oxide, combined with 

 an acid which is composed of an acid and of a chloride. When 

 it is saturated with bases the acid does not separate from it. 

 Any conjecture as to the composition of the acid and of the 

 chloride united with it would at present be premature. 



Stockholm, August 20, 1839. BeRZELIUS. 



II. Experiments on Mechanical Exosmose with reference 

 to determining the Existence of any difference of Magni- 

 tude hettsoeeji liquid and gaseous Particles. By Julius 

 Jeffreys, M.R.C.S. late of the Hon. East Lidia Company^s 

 Bengal Medical Service.^' 



Tj^XPERIMENTAL inquiries into the molecular constitu- 

 -^ tion of bodies, being in their nature very difficult, no 

 means of bringing the position or the relative magnitude of 

 their particles under observation have, so far as I am aware, 

 suggested themselves, if we except a faint light which of late 

 electricity, crystallography, and optics have beautifully thrown 

 in among them. 



The subject having been of too much interest and import- 

 ance to be neglected, much speculation has supplied the place 

 of experiment. In physical inquiries, however, hypothesis, 

 valuable in connexion with experiment, is dangerous to phi- 

 losophy without it, and I should not venture a word of the 

 former, but in its relation to the latter. 



The experiment I have to relate may be called, in the abs- 

 ence of any other term, mechanical exosmose. It was per- 

 formed indeed in 1829, some years before this word was intro- 

 duced, to denote the interesting phsenomena brought to light in 

 connexion with the diffusion of fluids, and it served, I think, 

 to determine something regarding the relative magnitude of 

 liquid and gaseous particles. Though it did not lie in my 

 power at the time to subject to trial more than one gaseous 

 fluid, the experiment not only went to compare the size of its 

 particles with liquid heterogeneous ones, but with such as are 

 homogeneous also. It appeared to establish in a manner suf- 

 ficiently conclusive, a considerable diff'erence between the 

 magnitude of particles of the same body in its liquid and 

 gaseous state. 



Moreover, though limited to a few subjects, a wider object 



* Communicated by the Author. 



