
by Cathode and Canal Rays to Exciting Current. 195 
experiments bearing on this point. This was accomplished 
by means of the movable collecting electrode in the barometer- 
tube, and the quantity of the incident rays observed for 
Fig. 3. 
Absorption curves of canal rays in air. 

yi 
eB ee ae: 
Curve I. Pressure of 0:24 mm. of mercury. 
» i. Pressure of 0°15 mm. of mercury. 
Ww | Pressures of 0:10-0:09 mm. of mercury. 
” * ) Potentials of 500-1000 volts. 
Iv j Pressures of 0:06 and 0:09 mm. of mercury, 
“ " | Potentials of 1000-2000 volts. 
| Pressures of 0-01 and 0:06 mm. of mercury. 
” * ) Potentials of 2000-5000 volts. 
various distances and various pressures. In figs. 3-8 the 
absorption of the rays in air, oxygen, and hydrogen is 
