92 McCieLtLanp— On the Emanation given off by Radium. 
same direction. The direction of the deflection of 4 divisions obtained when the 
air contained emanation was the same as that obtained without emanation. 
Judging not only from this particular experiment, but from several others, we 
are safe in saying that the emanation did not carry a charge sufficient to produce 
a deflection of more than 1 scale-division. 
The experiment did not, therefore, detect any charge on the emanation ; but it 
is important to calculate whether or not the emanation might be charged, and the 
charge be less than what could have been detected in the above experiment. 
Let us suppose that each emanation particle has a charge equal to. that carried 
by the gaseous ion; we have no case of a charge less than this, so that if the 
emanation is charged, its charge is probably at least equal to that of the gaseous 
ion, and may be greater. Denote this charge by ¢ in electromagnetic units. 
The capacity of the electrometer and connexions was ‘000149 microtarad ; 
and 1 scale-division corresponds to a potential difference between the quadrants 
of ,, of a volt. A deflection of 1 scale-division would therefore be produced by 
putting into the vessel D a charge of 
108 | 
60. 
or, by admitting into D, 
x :000145 x 10° = 24 x 10 electromagnetic units, 
24 x 10™ 
emanation particles. 
Again, the radiation from the emanation admitted into D in the above 
experiment produced such an ionisation that, when 7 was kept at a high 
potential, D got a charge corresponding to 100 scale-divisions in 47 seconds, 
with a capacity of ‘1 microfarad joined to the electrometer. 
This charge is produced by ions giving up their charge to D, the charge of 
each ion being e. 
The charge given to D per second is 
LOD iO? OP ee ; é ae 
WT x 80 x mi = 35 x 10-" electromagnetic units. 
The number of ions of either sign produced in D by the radiation from the 
emanation is therefore 
Bo 9¢ MO? 
; per second. 
Each particle of emanation is therefore producing ions in the surrounding gas at 
the rate of 
x 1Oe i 
ee 1-4 x 10° per second. 
We see, therefore, that as the emanation, when admitted into D, did not 
produce a deflection of more than 1 scale-division, it must either be uncharged, or, 
