vi] PROPERTIES OF THE RADIATIONS 173 
For an increase of voltage of 8 times, the current only increases 
about 3 times. The current in the liquid thus tends to become 
“saturated” as does the ordinary ionization current through a gas. 
These results have an important bearing on the ionization theory, 
and show that the radiation probably produces ions in the liquid as 
well as in the gas. It was also found that X rays increased the 
conductivity to about the same extent as the radium rays. 
Becquerel! has recently shown that solid paraffin exposed to 
the 8 and y rays of radium acquires the property of conducting 
electricity to a slight extent. After removal of the radium the 
conductivity diminishes with time according to the same law as for 
an ionized gas. These results show that a solid as well as a liquid 
and gaseous dielectric is ionized under the influence of radium 
rays. 
114. Effect of temperature on the radiations. Becquerel’, 
by the electric method, determined the activity of uranium at the 
temperature of liquid air, and found that it did not differ more 
than 1 per cent. from the activity at ordinary temperatures. In 
his experiments, the a rays from the uranium were absorbed before 
reaching the testing vessel, and the electric current measured was 
due to the 8 rays alone. P. Curie® found that the luminosity of 
radium and its power of exciting fluorescence in bodies were 
retained at the temperature of liquid air. Observations by the 
electric method showed that the activity of radium was unaltered 
at the temperature of liquid air. If a radium compound is heated 
in an open vessel, it 1s found that the activity, measured by the 
a rays, falls to about 25 per cent. of its original value. This is 
however not due to a change in the radio-activity, but to the 
release of the radio-active emanation, which is stored in the 
radium. No alteration is observed if the radium is heated in 
a closed vessel where none of the radio-active products are able 
to escape. ; 
3 C. R. 136, p. 1173, 1903. 
2 C. R. 133, p. 199, 1901. 
® Société de Physique, March 2, 1900. 
