:>32 



Prof. J. Patterson on the Ionization in 



Wilson and Elster and Geitel in their experiments measured 

 the amount of the ionization with specially constructed 

 electroscopes. This method of determination requires con- 

 siderable time for a single observation, and. moreover, could 

 not be used to measure the ionization at different tempera- 

 tures. E-utherford *, by using a large volume of gas and a 

 fairly sensitive electrometer, succeeded in measuring the 

 ionization. This latter method was employed in the present 

 investigation. 



In the experiments at different temperatures it was hoped 

 that by using quartz one would be able to get good insulation 

 at temperatures up to 400° or 500° C. A quartz tube with 

 walls about 1 mm. thick was made, but it would not insu- 

 late above 250° C, consequently all the insulation had to be 

 in the cold. 



The air was contained in a wrought-iron cylinder 30 cms. 

 in diameter, 20 cms. long, and containing 12,800 c. c. The 

 general arrangement of the apparatus is shown in fig. 1. A 

 is the cylinder supported on a tripod (not shown in fig.) 

 resting on ebonite blocks. It was heated with a gas furnace. 



Fis-. 1. 



The tube B was screwed into the cylinder : inside this was 

 the tube C insulated and supported by two ebonite rings E : 

 inside this again was the aluminium electrode D, insulated 

 and supported by the ebonite plug F, which was kept cool 

 by means of a water jacket. The horizontal tubes were 

 screwed into the uprights at the elbow and could thus be 

 * Bulletin of tlie American Physical Society, vol. ii. Xo. 4, p. 59. 



