58 THE ROYAL SOCIETY OF CANADA 
bubbling air through the solution at a uniform rate. In this way it 
was hoped to be able to obtain some curve which would show how the 
release of emanation varied with the temperature, and by means of 
determinations at definite temperatures between room temperature 
and the temperature of boiling water, to interpolate for intermediate 
temperatures. At 100° C. Boltwood has shown that all the emanation 
can be expelled. 
Apparatus. The following apparatus was necessary— 
(a). An electroscope and ionisation-chamber combined. 
(b). A gasometer. 
(c). A motor-pump. 
(d). Drying-bottles. 
(e). A radium solution of suitable strength, with a two-hole 
rubber stopper for bubbling air through. 
(Ae. Ae microscope. 
(g). A chronometer. 
(h). A thermometer. 
(4). A thermostat. 
(a). The ionisation-chamber was made of sheet-tin, cylindrical 
in shape, 15 cms. in diameter and 26 cms. high. There was one small 
circular hole in the top, through which a copper rod was fixed in posi- 
tion by means of sulphur insulation in a vulcanite collar. The copper 
rod extended down to the inlet and 3 or 4 cms. above the top for the 
purpose of attaching the gold-leaf. Another sheet-tin vessel was then 
sealed down over the top of the ionisation-chamber, forming the 
electroscope proper. It was 9 x 8 x 12 cms., provided with two mica 
windows for observation of the movement of the gold-leaf, and a small 
circular opening in the top through which a charging-key was passed, 
being fixed in position and insulated by sulphur and vulcanite. 
(b). The gasometer. The diameter of the inner cylinder was 
56 cms. and the available length 90 cms. A steel band passing over a 
pulley served to balance it in position, and heavy weights placed on 
the top of it furnished the necessary air-pressure. Through one of 
the stop-cocks on the top of the cylinder the air was forced into it, 
and it was then allowed to pass out through another. Rubber and 
glass tubing were connected to this stop-cock, and the current of air 
passed first into two bottles containing sulphuric acid. It was then 
bubbled through the radium solution, next through another sulphuric 
acid bottle, and finally into and out of the ionisation-chamber. The 
sulphuric acid bottles were for the purpose of removing the moisture 
from the air, which had been in contact with the water, both in the 
gasometer and in the flask containing the radium solution. 
