Mr. J. Cockle on the Solution of certain Problems. 181 



merit of the operation the dense fluid must have passed with 

 the same velocity through the membrane as the rare one, 

 which is contrary to the second fact. Therefore, in case of 

 diffusion of two fluids of unequal densities through a porous 

 partition, the fluid must accumulate on that side of the parti- 

 tion on which is situated that fluid which passed through it 

 most slowly. 



This explanation is applicable in all cases in which the 

 rarer fluid on the one side of the membrane has the same 

 chemical properties as that on the other side, their difference 

 being only in their degree of density. 



If these fluids be dissimilar in respect to their chemical qua- 

 lities, still the accumulation will take place on that side of the 

 membrane on which was situated the fluid which passed 

 through it most slowly, although its density may be less than 

 the other; thus, for instance, when a bladder full of air is 

 surrounded with carbonic acid, the latter enters faster than 

 the former escapes, and the bladder bursts. Now it is found 

 by experiment, that carbonic acid passes through wet mem- 

 brane quicker than atmospheric air, although of a greater 

 density. 



In such instances the relative velocities of the passage of 

 different fluids through membrane will be influenced by their 

 chemical attraction for the material of which the membrane is 

 composed, as well as by that attraction which is regulated by 

 quantity of matter ; and in some cases the existence of the 

 latter force may be so modified by the former as to be wholly 

 inappreciable ; but still that force, being an universal agent, 

 and acting upon all matter according to invariable laws, is 

 in operation in every instance where the conditions requisite 

 for endosmose and exosmose are present, although in some 

 cases chemical attraction or electricity may have no demon- 

 strable existence; and therefore it may be looked upon as the 

 essential cause of endosmose and exosmose, chemical affinity, 

 electricity, &c. being merely the modifiers of its operation, 

 and in respect to it, secondary agents. 



XXXIII. On some Formula which serve to indicate the limits 

 of the application of Indeterminate Methods to the solution 

 of certain Problems. By James Cockle, M.A., of Trinity 

 College, Cambridge*. 



r T , HE equations distinguished below by unaccented num- 

 bers will respectively be found at p. 34-4<, or one of the 

 four succeeding pages, of the Report of the Sixth Meeting of 

 * Communicated by Sir George Cayley, Bart. 



