Absorption of Gas in a Crookes Tube. 505 



D, E. C served as a reservoir in which gas could be dried 

 at a pressure of a few centimetres and kept ready for use ; 

 this was necessary, as it was found that unless well-dried gas 

 was worked with, consistent results could not be obtained. 



W 



Small charges of gas could be admitted to the tube N by 

 alternately opening and closing first D and then E. 



F was useful in the admission of prepared gases to the 

 bulb C, and in allowing the partial exhaustion of the apparatus 

 by a water-pump. 



H leads to a McLeod gauge; J is another drying-bulb 

 containing P 2 5 , and serves to dry the whole of the space 

 shut off from C. By this means, if necessary, N could be 

 replaced by another experimental tube and dry gas still kept 

 inC. 



The mode of conducting an experiment was as follows : — 

 A suitable pressure, about 1 mm., was established in ~N } and 

 a current of known value from a large battery was passed for 

 half an hour. A few minutes were allowed for cooling, and 

 then a second reading of the pressure was taken. 



The current could be measured by means of an insulated 

 galvanometer, and it could be brought to any desired value 



Phil. Mag. S. 6. Vol. 1. No. 4. April 1901. 2 L 



