Letter from Horace T [Tabberer] Brown, 52 Nevern Square, Kensington, to [Joseph] Larmor The cause of the misunderstanding lies with the term transpiration. He gives Graham's use of it and he was unaware it could be used in another sense. In the extreme case that Larmor imagines, the diameter law would have no application, but porous diffusion would occur before that circumstance. He gives an example of a fine septum separating hydrogen from carbon dioxide. He can see his way to some experimental work on these points, which he might take up next winter, if no-one else does. 13 June 1900