It is also noted that a difference in the levels has occurred, and that the liquid in the tube now rises to a considerable height.

It must therefore be admitted that the flow of the water has been more rapid than that of the alcohol.

At the commencement, the water must have penetrated into the tube much more rapidly than the alcohol left it.

Hence the difference in the levels, and, consequently, a difference of pressure on the two faces of the membrane.

This difference goes on increasing, reaches a maximum, then diminishes, and vanishes when the diffusion is complete, final equilibrium being then attained.
The phenomenon is evidently connected with diffusion.