740 
Mr. S. Russ on the Electrical Charge 
attaining a maximum value at about 5 cms. pressure, then 
falling abruptly at a pressure of about '2 cm. 
Owing to the very short life o£ the emanation from actinium 
(3*9 seconds) the distribution of the emanation in the cylinder 
C must be very different at the different pressures employed. 
At atmospheric pressure the emanation, owing to its rapid 
change into actinium A, will be confined to a comparatively 
small region round D, and the active deposit particles will have 
a greater distance to go before reaching the wires A and B 
than at the reduced pressures. It is probable that the decrease 
in the ratio of the activity of the cathode to that of the 
anode between pressures of 5 cms. and 2 mms. corresponds 
to the similar effect with thorium which has been already 
mentioned. 
It is worth noting that the activity observed on the anode 
is almost entirely due to some of the active deposit particles 
being negatively charged. This w r as shown as follows : — 
An experiment was made in which no field existed between 
the wires and the containing cylinder, the activity observed 
on either of the wires was only about one-seventh part of 
that observed on the positive electrode. Hence the above 
conclusion. 
At this stage it was resolved to vary the conditions of the 
experiment. 
A preparation of actinium was placed at the bottom of a 
cylindrical vessel A (fig. 3) 9 cms. long and 4*5 cms. diameter, 
Fiar. 3. 
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ACTI/VIUW 
which ,wasiclosed by a rubber stopper through which passed 
two brass rods carrying two vertical brass plates B and C ; 
