370 Mr. R. K. McClung on the Relative Amount of 
General Comparison of the Ionization in Different Gases. 
A series of determinations of the relative amount of ioniza- 
tion in the several gases already mentioned was made both 
for the case of comparatively soft rays and for considerably 
harder ones, each gas being as usual compared withair. The 
softer rays were produced by the automatic regulating bulb 
No. 1, and were comparatively easily absorbed. <A sheet of 
lead of about 0°3 mm. in thickness placed in the path of the 
rays was capable of stopping practically the whole effect of 
the rays given out by this bulb. The harder rays were pro- 
duced by bulb No. 3, which, previous to making this series 
of experiments, was run by means of a large coil and mercury 
break for a considerable time, so that it produced com- 
paratively hard rays. The rays given out by it were much 
harder than those which it produced when the determinations 
given in Table I. were made with this bulb. In making 
these comparisons with the hard rays, a sheet of lead of 
about 0°3 mm. in thickness was placed in the path of the rays 
so that all the softer rays were cut off, and only the harder 
ones which were able to penetrate the lead produced the 
ionization in the cylinders. Hvyen with this thickness of 
absorbing lead, very considerable effects were produced in the 
ionizing vessels. ‘The two series of determinations are given 
in Tables VI. and VII. 
TasLE VI.—Relative Ionization for Soft Rays. 
| ame of Gao, | Tonialion relative to | Gt aie taken 
unity. 
UPL dp dda POE, 1-0 1-0 
Hydrogen’... 2.5% 0105 0069 
| sOmypentt.s 1. Sees a 1°30 1:105 
Carbon Dioxide...... 1°46 1°529 
Sulphur Dioxide ..., 11:05 | 2:193 
TaBLE VIJ.—Relative Ionization for Hard Rays. 
| 
Ionization relative to Air 
Name of Gas. ; 
taken as unity. 
£0 aL a. 1:0 
Pyrogen? oy, ope tees 0-177 
CCS ae ao ae i 
| Carbon Dioxide............ 1°33 
| Sulphur Dioxide ......... | 4-79 
