. III. THEORY OF ENDOSMOSE. 49 



assuming this law to be true in all cases, syrup, whose 

 density is 1/3, produces a current capable of raising a 

 column of mercury of 127 inches (3 metres 42 centimetres,) 

 or what amounts to the same thing, equal to the enormous 

 pressure of 4^ atmospheres. 



Theory of Endosmose. Dutrochet has endeavoured to 

 give an explanation of the phenomena of endosmose ; and 

 Poisson and Becquerel have proposed others. Thus, some 

 ascribe endosmose to the action of an electric current de- 

 veloped by the contact of the two different liquids ; a cur- 

 rent which will produce the passage of the water through 

 the membrane, from the positive to the negative pole, as in 

 the well-known experiment of Porret. But to render this 

 explanation probable, it would be necessary to prove that 

 the contact of water with alcohol, solution of sugar, &c., 

 developes electricity ; which is not the case. Poisson sup- 

 posed that the least dense liquid entered the capillary tubes 

 of the membrane, and that this capillary thread, drawn 

 down by the pure water, and up by the denser liquid, must 

 be elevated in virtue of molecular attraction. But this ex- 

 planation becomes inadmissible when we consider that al- 

 cohol, which is lighter than water, produces endosmose ; 

 and that certain calcareous and siliceous stones, placed un- 

 der the same conditions as membranes and plates of clay, 

 do not give rise to the same effect. 



Up to the present time we have not any satisfactory theory 

 of endosmose; but we know that the general conditions of 

 the phenomena are as follow : 



1st. That the two liquids should have an affinity for the 

 interposed membrane. 



2dly. That the two liquids should have an affinity for 

 each other, and be miscible. 



If one of these conditions be wanting, endosmose does 

 not take place. Experiment proves that the current of en- f 

 4 



