UQUIDS AND ALLIED EXPERIMENTS. I3 



The decision as to the applicability of either of these, or similar hypoth- 

 eses, can not be given until the work is repeated with an artificial atmos- 

 phere of hydrogen at/ in fig. 3, in place of air; or after other similar varia- 

 tions of experiment. The results (§20) show that in the earlier stages of 

 the work, at least, the behavior throughout is then totally different. Hence 

 it is necessary to investigate the question from a broader point of view and 

 relative to the two simultaneous diffusions in opposite directions through 

 the same channel. 



15. Continued. Influx of Air into the Imprisoned Hydrogen. — In view 

 of the fact that for a single gas w increases uniformly in the lapse of time, 

 the initial counterflux of air may also be computed directly, independent 

 of the flow of hydrogen. In this way additional light is thrown upon the 

 phenomenon, preliminarily. Thus if k^ and p^ refer to air 



.,,^KadpJdl=Ka ^-^=;^^p^" =*,- 74.2. X. 3.6X98. ^^, 



where p^ is zero at the beginning of the experiment and where k^ has the 

 value found in §19, i.o9Xio~^\ Hence ^^ = 5. 89X10"^ grams/sec. or 

 5. 09 X I o~^ grams/day. Initially {t — o sec), therefore, the swimmer should 

 gain 5.1 mg. per day, due to the influx of air into the imprisoned hydrogen. 

 In the lapse of time this rate would naturally be much reduced in conse- 

 quence of the counter-pressure of the air accumulating in the swimmer; 

 nevertheless the initial rate of influx (5.89X10"^ grams/sec.) is so large, as 

 compared with the observed rate of efflux, 6.29X10"^" grams/sec. in table 2, 

 as to show that two counter-currents of air and hydrogen are simultaneously 

 transpiring, at rates relatively not very different in value. It is therefore 

 necessary to investigate these currents in detail. 



16. Continued. Coefficients Depending on Diffusion Gradients. Trans= 

 piration. — This case might at first seem improbable. If the hydrogen 

 diffuses outward under full barometric pressure at v, fig. 3, there being no 

 hydrogen at /, the air must diffuse inward from / to v, since there is no 

 air originally at v; but when the hydrogen has nearly vanished, or its 

 pressure excess at v is equivalent to a diffusion gradient h"py:g along Jv, 

 the air or a mixed air-hydrogen gas would again have to diffuse outward, 

 due to the specified head or increment of pressure at v as compared with /. 

 Such complications would hardly be expected in so simple an experiment 

 and yet this is precisely what seems to take place. I have therefore developed 

 the equations tentatively as follows. 



Let pj^ and p^ be the pressures of hydrogen and of air at any time at v, 

 fig. 3. Let B be the constant barometric pressure during diffusion and vr 

 the vapor pressure of water. Then 



B+h"p,g = p^-\-p^+7r (8) 



where the constant U. = p,,-\-p^ = B-\-h"p^g — ir may be used for abbreviation . 



