493 
Using the same methods as described abov-e, the ionisation chamber (T) 
is constructed. No mica windows are needed in the front door or the 
back side of (this ionisation) Chamber. The dimensions of (I) are 12 x 12x 
12 cm., and the thickness of the walls is 1.7 mm. With the exception of the 
mica window the door to the ionisation chamber is constructed like that of 
the door to the gold leaf box. The front door should be hinged to the 
box and the back side can either be permanently soldered to the box or it 
can be fastened by means of hinges. 
The two boxes (E) and (1) are fastened together by screws, the right 
hand sides being flush with each other as shown in Fig. 1. This arrange- 
