Mr. Graham has obtained many pure aqueous solutions of organic and inorganic matter, most of them being unstable. Ice near or at its melting point is believed to be a colloid body, consequently it is unstable and resembles a firm jelly, having a tendency to rend and recombine. ‘The constant intervention of colloid septa in so many of the phenomena of animal and vegetable life gives to the subject of dialysis a high physiological interest, and it will doubtless exercise an important influence on the progress of physiological research.’[12] Subsequently to these researches Mr. Graham published a memoir on a new method of analysing gases which he had called atmolysis. The memoir may be regarded as consisting of four parts, the first of which is preliminary, being on the reciprocal diffusion of gases through porous plates. The next three parts relate to effusion, or the passage of gases under constant pressure through a minute opening in a very thin plate into a vacuum; transpiration, or the passage of gases through capillary tubes into vacuo; and lastly atmolysis, which is the partial separation of a mixture of gases and vapours of different degrees of diffusibility by permitting them to diffuse themselves through a porous plate into a vacuum: a new kind of analysis, which possesses a practical character of extensive application. The diffusing instrument employed by Mr. Graham was a cylindrical glass tube about an inch in diameter, ten inches long, with one end closed by a very thin porous disc of compressed artificial graphite fixed by a resinous cement. While the tube was being filled with hydrogen gas over a trough of mercury, the escape of the gas was prevented by covering the graphite very carefully with a thin sheet of gutta percha. As soon as the gutta percha was removed, the reciprocal diffusion of the gases began, and in from forty to sixty minutes the whole of the hydrogen had escaped from the tube, and a quantity of atmospheric air amounting to about one fourth of the volume of hydrogen had entered the tube and taken its place, according to the ordinary law of the diffusion of gases. During this time the mercury rises in the tube so as to form a column several inches high, a fact which is a striking demonstration of the intensity of the force with which the reciprocal penetration of different gases effected.