Mitchell on the Penetrativeness of Fluids. 107 



bladder actually burst in the neck, in withdrawing it from under the 

 receiver. It was found to contain thirty-five parts carbonic acid gas 

 by volume in one hundred. The substance of the bladder was quite 

 fresh to the smell, and appeared to have undergone no change. The 

 carbonic acid gas remaining without in the bell-jar had acquired 

 a very little coal gas. 



* The conclusion is unavoidable, that the close bladder was inflafed 

 by the insinuation of carbonic acid gas from without. 



* In a second experiment, a bladder containing rather less coal 

 gas, and similarly placed in an atmosphere of carbonic acid gas, 

 being fully inflated in fifteen hours, was found to have acquired forty 

 parts in one hundred of this latter gas, a small portion of coal gas 

 left the bladder as before. 



1 A close bladder, half filled with common air, was fully inflated 

 in like manner, in the course of twenty-four hours. The entrance 

 of carbonic acid gas into the bladder depends, therefore, upon no 

 peculiar property of coal gas. The bladder partially filled with coal 

 gas did not expand at all in the same jar containing common air or 

 water only. 



* M. Dutrochet will probably view, in these experiments, the dis- 

 covery of endosmose acting upon aeriform matter, as he observed it 

 to act upon bodies in the liquid state. Unaware of the speculations 

 of that philosopher, at the time the experiments were made, I fabri- 

 cated the following theory to account for them, to which I am still 

 disposed to adhere, although it does not involve the new power. 



' The jar of carbonic acid gas standing over water, the bladder was 

 moist, and we know it to be porous. Between the air in the bladder 

 and the carbonic acid gas without, there existed CAPILLARY CANALS 

 through the substance of the bladder filled with water. The surface 

 of water at the outer extremity of these canals being exposed to car- 

 bonic acid gas, a gas soluble in water would necessarily absorb it. 

 But the gas in solution, when, permeating through a canal, it arrived 

 at the surface of the inner extremity, would rise as necessarily into 

 the air in the bladder and expand it. Nothing but the presence of 

 carbonic acid gas within could prevent the disengagement of that 

 gas. The force by which water is held in minute capillary tubes 

 might retain that liquid in the pores of the bladder, and enable it 

 to act in the transit of the gas even after the pressure within the 

 bladder had become considerable.' 



A careful perusal of Mr. Graham's notice will excite in every 

 one who knows the value of experimental interrogation, an expres- 

 sion of surprise, at the failure, on the part of that intelligent and 

 ingenious chemist, to pursue, in the only true spirit of science, the 

 investigation of a principle, one of the most striking manifestations 

 of which had thus been placed conspicuously before him. Content 

 with a single additional experiment, he comes, in the ancient method, 

 to immediate conjectural explanation, and has thus lost an easy 

 opportunity of making a beautiful, and, perhaps, extensively useful 



