804. The velocity and strength of these currents are capable of exact admeasurement. The amount of endosmose is measured by an apparatus termed an endosmometer, which consists of a small bottle, the bottom of which is taken out and the aperture closed by a piece of bladder. Into this bottle is poured some dense fluid; the neck of the bottle is closed with a cork, through which a glass tube, fixed upon a graduated scale, is passed. The bottle is then placed in pure water. The water by endosmose penetrates the bottle in various quantities according to the density of the fluid contained in its interior through the membrane closing its bottom. The dense fluid in the bottle, increased in quantity by the addition of the water, rises in the tube fitted to its neck, and the velocity of its ascent is the measure of the velocity of the endosmose. 805. The strength of endosmose is measured by a similar apparatus, in which a tube is twice bent upon itself, and the ascending branch containing a column of mercury which is raised by the fluid in the interior of the endosmometer, as the volume of this fluid is increased by the endosmose. By means of these two instruments it is found that the velocity and strength of endosmose follow the same law, and that both are proportionate to the excess of the density of the fluid contained in the endosmometer above the density of water. By numerous experiments it is ascertained that by employing syrup of ordinary density (I. 33) an endosmose is obtained, the strength of which is capable of raising water more than 150 feet. 806. But though difference of density is necessary to the production of endosmose, yet numerous and decisive experiments show that the different natures of fluids, irrespective of their proportionate densities, materially influence the activity and energy of the process. Thus, if sugar-water and gum-water of the same density be placed in the same endosmometer, the former produces endosmose with a velocity as seventeen and the latter only as eight. The endosmose produced by a solution of the sulphate of soda is double that produced by a solution of the hydro-chlorate of soda of the same density. A solution of albumen exerts an endosmose four times greater than a solution of gelatin of the same density. 807. With organic fluids endosmose goes on without ceasing until the chemical nature of the fluids becomes altered by putrefaction; but with alkalies, soluble salts, acids, and chemical agents in general, the endosmose excited is capable only of short continuance, because such agents enter into chemical combination with the organic tissue of the endosmometer, and thus destroy endosmose.