. Carnegie Institution of Washington publication. THE DIFFUSION OF GASES THROUGH ancy which will be felt in the lapse of time. The question will be discussed in the next chapter. 4, Equations. Manipulation.—Let h be the difference of level of the impris- oned water and the free surface in the reservoir R. Then it follows easily that Rm T h+H' (i). Fig. 2.—Cylin- drical diver. p„ gM (i+m/M)-py,/pg where // is the corrected height of the barometer (from which the mercury head equivalent to the vapor pressure of water is to be deducted), pm, Pw, Pa, the densities of mercury (o° C), water {t° C),
. Carnegie Institution of Washington publication. THE DIFFUSION OF GASES THROUGH ancy which will be felt in the lapse of time. The question will be discussed in the next chapter. 4, Equations. Manipulation.—Let h be the difference of level of the impris- oned water and the free surface in the reservoir R. Then it follows easily that Rm T h+H' (i). Fig. 2.—Cylin- drical diver. p„ gM (i+m/M)-py,/pg where // is the corrected height of the barometer (from which the mercury head equivalent to the vapor pressure of water is to be deducted), pm, Pw, Pa, the densities of mercury (o° C), water {t° C), and glass, respectively, m the mass of the imprisoned air at v, R its gas constant, and t=/ + 273° its absolute temperature. M is the mass of the glass of the swimmer and g the acceler- ation of gravity. The equilibrium position of the swimmer is unstable. To find it R may be raised and lowered for a fixed level of the swimmer; or R may be clamped and the proper level of the swimmer determined by suction and release at C. The dropping of the swimmer throughout the column of water may occasion adiabatic change of temperature of °. It was my practice in the present experiments to use the latter method and to indicate the equilibrium position of the swimmer by an elastic steel ring encircling A. In this way the correct level may be found to about i mm. and afterwards read off on the cathetometer. After making the observations, the hose ah is to be separated at a, so that the swimmer falls to a support some distance above the bottom, admitting of free passage for diffusion. Clearly this diffusion is due to the difference of level, h", between the water in v and at the free surface of the liquid (see fig. 2). Increase of barometric pressure has no differential effect. A large head //", however, means a longer column for diffusion. 5. Data.—In table i a few of the data made in 1900 are inserted, chosen at random. In the intermediate time I did not return to
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