192 Mr M c Glung, Investigation of the effect of Temperature 



the diagram, neatly overlapping at the junction. The plate P is 

 then screwed down as tightly as possible to the flange with heavy 



ffi 



F 



i/M 



£ 



W 



Fig. 1. 



screws until the lead is flattened down to about half its thickness. 

 By this means an air-tight junction was obtained which has proved 

 very satisfactory, and which would stand the highest temperature 

 and pressure employed in the experiment. This device was the solu- 

 tion of one of the greatest difficulties in designing the apparatus. 

 The end of the cylinder must be of aluminium, as being the only 

 metal which could be satisfactorily employed as a window to allow 

 the rays to pass into the cylinder, and it was also necessary to have 



