126 Ingvar Jorgensen and Walter Stiles. 
summarises their results with regard to carbon dioxide. Similar 
results were obtained with water vapour. 
Table VIII. 
Diffusion of carbon dioxide through apertures of various sizes. 
Diameter of 
aperture. 
CO 2 diffused per 
hour. 
CO 2 diffused 
per sq. cm. 
per hour. 
Ratio of 
areas of 
apertures. 
Ratio of 
diameters of 
apertures. 
Ratio of CO , 
diffused in unit 
time. 
22-7 
•2380 
•0588 
1-00 
1-00 
100 
1206 
•09280 
•0812 
•28 
•53 
•39 
1206 
•10180 
•0891 
•28 
•53 
•42 
603 
•06252 
•2186 
•07 
•26 
•26 
5-86 
•05558 
•2074 
•066 
•25 
•23 
3-23 
•03988 
•4855 
•023 
•14 
•16 
3-22 
•03971 
•4852 
•020 
•14 
•16 
2-12 
•02608 
•8253 
•008 
•093 
•10 
2-00 
•02397 
•7629 
•007 
•088 
•10 
In order to explain this result, Brown and Escombe consider 
first the case of a disc capable of absorbing carbon dioxide and freely 
exposed to the air. If the latter is perfectly still, convergent streams 
of carbon dioxide will creep through the air towards the disc to 
replace that absorbed, and a steady gradient of density will be 
established, and if surfaces are drawn passing through all the points 
of the same carbon dioxide density, these surfaces will form ‘ shells ’ 
surrounding the disc. If the disc is a perfect absorbent of carbon 
dioxide, these shells will vary in density from zero at the absorbing 
surface to a maximum density which is that of carbon dioxide in 
air. This will theoretically be at an infinite distance from the disc 
but is practically reached at a point 5 or 6 diameters from the disc. 
Now Stefan has examined mathematically the exact converse of 
this case, namely, evaporation from a circular surface of liquid. 
Stefan obtained the following formula for the amounts of evapor¬ 
ation from such a surface :— 
M = 4ka 
P—p' 
Where M is the mass of liquid evaporated in a given time, k 
the coefficient of the diffusion of the vapour, a the radius of the disc 
of liquid, P the pressure of the atmosphere and p' and p" the 
pressure of the vapour at the surface and at an infinite distance 
from it respectively. 
The formula given by Larmor for the absorption of carbon 
dioxide by a perfectly absorbing disc, assuming the formation of 
