Vit] RADIO-ACTIVE EMANATIONS 211 
In the light of the results described in section 116, the gas, given 
off by the radium, was probably the non-active gases, hydrogen 
and oxygen, in which the active emanation was mixed in minute 
quantity. It will be shown later (section 163) that the energy 
radiated from the emanation is enormous compared with the 
amount of matter involved, and that the effects observed, in most 
cases, are produced by an almost infinitesimal amount of the 
emanation. 
In further experiments, Curie and Debierne? found that many 
substances were phosphorescent under the action of the emanation 
and the excited activity produced by it. In their experiments, two 

Se Material 
Fig. 40. 
glass bulbs A and B (Fig. 40) were connected with a glass tube. 
The active material was placed in the bulb A and the substance 
to be examined in the other. 
They found that, in general, substances that were phosphores- 
cent in ordinary light became luminous. The sulphide of zine was 
especially brilliant and became as luminous as if exposed to a 
strong light. After sufficient time had elapsed, the luminosity 
reached a constant value. The phosphorescence is partly due to 
the excited activity produced by the emanation on its surface, and 
partly to the direct radiation from the emanation. 
Phosphorescence was also produced in glass. Thuringian glass 
showed the most marked effects. The luminosity of the glass was 
found to be about the same in the two bulbs, but was more marked 
in the connecting tube. The effect in the two bulbs was the same 
even if connected by a very narrow tube. 
Some experiments were also made with a series of phosphores- 
cent plates placed in the vessel at varying distances apart. With 
the plates 1 mm. apart, the effect was very feeble but increased 
directly as the distance and was large for a distance of 3 cms. 
1 C. R. 133, p. 931, 1901. 
14—2 
