ACTION OF TERNARY ARRANGEMENTS. 29 



permint, and then expanding a bubble, the taste of the essential oil will be perceived 

 when a portion of the air is drawn back out of the bubble into the mouth. With other 

 oils, as cajeput, and with ethers, the effect is the same ; and it is to be observed, that 

 durin 1 * the transit thev work the surface of the bubble into a kind of microscopic waves, 

 and produce an iridescent play of colours. 



85. To obviate any exception that might be taken to the use of soapy matter in these 

 films, or to their excessive thinness, I have employed the arrangement of section 52, 

 which establishes the same truths. 



86. Into such a tube I threw 200 measures of hydrogen gas, and the same quantity 

 into one the upper extremity of which was hermetically sealed, by way of affording a 

 comparison. In the former, the thickness of the roof of water was about } inch, and in 

 24 hours the level of the water in it rose half an inch ; while in the latter it remained un- 

 disturbed, thus incontestably proving that hydrogen gas passes with great freedom through 

 masses of water. Nor is this permeability confined to that liquid alone : a tube which 

 was thus covered with a layer of lamp oil, in five days raised the level of the water in 

 it more than two inches ; and one the roof of which was of copaiba balsam, threw out 

 all the gas to within j of an inch of its top ; while a tube of the same size, but sealed 

 at the other end, that stood by them, kept its level 



87. It appears to me the reason that we have not hitherto understood the phenom- 

 ena of endosmosis, or the action of these ternary arrangements, as I have called them, 

 has arisen chiefly from the employment of substances as barriers, which were possessed 

 of pores of sensible size. A moment's consideration will place this in its true light : 

 suppose two gases were kept apart by the intervention of a plug of charcoal, in their 

 diffusion into each other, not only would those portions pass the barrier which were 

 brought along by a direct action, but a much larger quantity would slip through by 

 mere leakage among the pores (36). Bladder, tissues, stucco plugs, &c., which we 

 know to possess pores of sensible size, are open to this objection ; but the case is very 

 different with liquids, which, from their uniform condition and the close proximity of 

 their atoms, admit of no such action. A mass of stucco a foot thick would be subject 

 to this kind of mechanical derangement, but a sheet of water reduced to that excessive 

 degree of thinness that it is invisible, allows no gas to go through it by leakage, bat all 

 passes by absorption. 



88. The original experiment of Dutrochet on endosmosis, and those of Dr. Mitchell, 

 were examples of this class of ternary arrangements. In these cases, membranes or gum 

 elastic were tied over the mouths of vessels, and the result was shown by the swelling 

 or sinking of the barrier. These can be repeated in a more satisfactory manner with 

 liquids (52). 



89. In this experiment we also recognise an identity of results with those which have 

 heretofore excited so much attention, under the title Endosmose ; but understanding in 

 this case, as we do, the conditions under which the result is obtained, there is no dif- 

 ficulty in extending the explanation of one experiment to the other. Endosmose is only 

 a complex case of simple absorption. The mechanical results here obtained, the swell- 

 ing or sinking of the barrier, depend on the more rapid absorption of one gas by that 



