Ionization produced in Gases by Réntgen Rays. 369 
of oxygen, and the change took place in the same direction 
but was not quite so marked as in oxygen. The change in 
the type of rays did not have quite so great an effect in 
changing the relative amount of ionization in carbon dioxide 
and air as it did in the case of oxygen and air. The effect 
was, however, quite distinct, as is shown by the results}given 
in Table IV. 
Tasse LV. 
Length of Alternate Pressure in cylinder ' 
Spark-gap in mms. containing Carbon Dioxide. 
6°51 5641 mm. 
9°79 5742 ,, 
13:97 DISS 55 
19°74 580°6_,, 
Comparison of the Ionization in Sulphur Diowide and Air. 
Sulphur dioxide was experimented upon and treated in a 
manner exactly similar to that which has been described for 
the other gases. Results were obtained very similar to those 
obtained for oxygen and carbon dioxide, but the effect pro- 
duced by altering the type of rays was more marked in the 
case of sulphur dioxide than with oxygen or carbon dioxide. 
The change of ionization with change of rays took place in 
the same direction as it did in the case of the other two 
gases. The value of = when using the softer rays was 
11:05, but when the harder rays were used this value was 
reduced to 4°79. ‘I'he same result is shown by the experi- 
ments in which the type of rays was varied by altering the 
pressure in the bulb. The effect was quite marked, as is 
shown by the series of observations given in Table V. 
Tasie V. 
Length of Alternate | Pressure in cylinder | 
Spark-gap in mms. containing Sulphur Dioxide., 
6°09 69°3 mm. 
11°9 76°53 _,, 
16:75 SiR, 
19-09 | oyuial | ahe 
