104 ROYAL SOCIETY OF CANADA 
Obviously there are many causes for discrepancies. For instance, 
the charcoal in one tube may be more tightly packed than in another, 
although care was taken to have all three tubes the same in this respect. 
Again, the charcoal may not be of the same density or hardness through- 
out, and a difference in these qualities may mean a difference in its 
power of absorbing the emanation. It is possible that the absorption 
of the emanation is proportional to the surface of charcoal exposed to 
the emanation rather than to the quantity of volume of charcoal. For 
a uniform size of grain of the charcoal, the surface would be propor- 


120 
100 

“SAS 
10 FOR AMPS, 
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60 


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IONIZATION CURRENT, x 4/7 5x 
29 





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FLOW IN CC. PER 6EC. 
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tional to the volume, but in masses of charcoal where the grains or 
particles were not of uniform size the ratio of surface to volume in 
each mass may not be the same. In the present work an attempt was 
made to have the charcoal grains of about uniform size by sifting the 
charcoal through a set of sieves, and collecting separately the residues 
in the different sieves. 
From the mathematical discussion on the absorption of the eman- 
ation by different quantities of charcoal we should expect that 
there would be no difference in the ionization current in the testing 
vessel whatever the shape of the containing tube, if the quantity, that 
is, the volume, of the charcoal remained the same. One might think, 
however, that the charcoal would have a better chance to absorb, if the 
a 
