1897 - 98 .] The Passage of Water through Indiarubber Films. 263 
(2) That the rate of penetration depends upon difference of 
pressure of water-vapour on the two sides of the indiarubber, not 
upon hydrostatic pressure, and increases considerably with increase 
of temperature. 
(3) That indiarubber is similarly, but far more rapidly, penetrated 
by alcohol. 
(4) That it also permits diffusion of some substances dissolved in 
water. 
These facts may need to be taken into account in dealing with 
indiarubber, both in medical and scientific work. 
I am indebted to Professor Tait for his kind permission to work 
in his laboratory ; to Professor Crum Brown for references to the 
literature of the subject ; and to Dr Knott for assistance with the 
experiments and calculations. 
[Table 
