86 ROYAL SOCIETY OF CANADA 
current of air charged with the emanations of radium, thorium, or 
actinium is deprived of some or all of its emanation in the passage 
through a tube {filled with cocoanut charcoal, and for this purpose the 
charcoal need only be at ordinary temperature. The complete with- 
drawal of the emanation only takes place when the air is passed very 
slowly through the charcoal; if the speed is increased, the amount of 
emanation emerging is increased also. In another experiment Ruther: 
ford found that if a tube containing less than a gramme of the charcoal 
is open to a vessel containing the emanation from several milligrammes 
of radium bromide, in the course of time the emanation is absorbed by 

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Fie 1° 
the charcoal. If some powdered willemite is mixed with the charcoal 
the gradual absorption is shown by the increasing brilliancy of phos- 
phorescence of the willemite. It is not necessary to heat or exhaust 
the charcoal previously, but when either is done the emanation is more 
rapidly absorbed. The charcoal retains the emanation at ordinary 
temperature, but the greater part of it is expelled by heating to a low 
red heat. 
The phenomenon of the absorption of emanation is not only of 
much interest in itself, but also in the fact that it may be of use in 
