220 Wisconsin Academy of Sciences , Arts and LeUers. 
binations in pairs and separating them from each other by 
means of a membrane of vulcanized caoutchouc. He found the 
main current to be from the liquid which is the more readily 
imbibed by the rubber, through the septem to the less readily 
imbibed liquid. Again in 1900 1 he used water, methyl alcohol, 
amyl alcohol, amyl acetate, chloroform, benzene, ether, and 
ethyl alcohol. He employed hog’s bladder as a septem placing 
one side of it in contact with ethyl alcohol (the liquid which, 
of those named, is according to him imbibed least readily) and 
bathing the other side with each of the other liquids success¬ 
ively. He always found the main current to be in the direction 
toward the ethyl alcohol and the rate of flow to vary with the 
amounts of liquid imbibed by the membrane during the first five 
minutes, which amounts were, of course, determined by independ¬ 
ent experiments. I have confirmed all of the results of Flusin 
where he used rubber membranes. He says nothing, however, 
about the minor current,, which I found to be present in all of 
these cases to a greater or lesser extent. In other words, the rub¬ 
ber was traversed by both liquids of each pair, though the main 
direction of the current was quite correctly determined. Flusin 
shows that the affinity between membrane and liquid is to be 
measured by the rate with which the latter is imbibed by the 
former, and not by the total amount of liquid taken up by a 
given quantity of membrane at the end of a long time, as 
Tammann 2 contends. Raoult 3 separated methyl alcohol and 
ether from each other by means of rubber. He always found 
the direction of the main current to be from the ether 
through the rubber to the methyl alcohol; and the direction 
of the main current remained the same, even when the 
ether was considerably diluted with methyl alcohol. When 
he substituted a membrane of hog’s bladder for the rub¬ 
ber, the direction of the main current was reversed, it being 
from the methyl alcohol through the septum to the ether. In 
his article, Raoult has omitted to say anything about the fact 
that in his experiments there is also a minor current in a di- 
1 Compt. rend. 126, (1497) 1898; ibid. 131, 1308 (1900). 
2 Zeit. Phys. Chem. 22, 491 (1897). 
sCompt. Rend. 21, 187 (1895). Zeit. Phys. Chem. 17, 737 (1895). 
