of Gases exposed to Ronlgen Rays. 251 



order to make the gases conductors, and whether the absorption 

 was in any way related to the constitution or conductivity of 

 the gas. 



The absorption of energy in gases like air, hydrogen, oxygen 

 is small and is not easily detected unless a delicate null 

 method is used. 



Two equal and similar conical-shaped vessels ABC, A'WC/ 

 (fig. 2), much larger in diameter at the top than the bottom, 



Fig. 2. 



were placed in such positions that the axis of each cone 

 passed as nearly as possible through the anode of the focus- 

 bulb. From experiments it was found that the #-rays 

 appeared to emanate in all directions from the anode. The 

 upper parts of each vessel, A B, A'B', were made of lead, and 

 were separated from the lower portions B C, B'C, which were 

 made of glass, by thin ebonite plates. Thin ebonite plates 

 also covered the ends of the glass cylinders at C and C, so 

 that the vessels B C, B'C' were air-tight, and could be ex- 

 hausted when required. 



The lead cylinders A B_, A'B' were used to compare the 

 rate of leak after the rays had passed through the glass cylin- 

 ders. Insulated wires D E, D / E / formed the electrodes,* and 

 these were connected to opposite pairs of quadrants of the 

 electrometer, and both quadrants were at first charged up to 

 the same potential, which in practice was generally 200 volts. 

 The outsides of the vessels AB, A / B / were connected to 

 earth. 



