
248 RADIO-ACTIVE EMANATIONS [CH. 
energy corresponding to 40,000 horse-power days. In order to 
obtain such an amount of emanation about 70 tons of radium 
would be required. 
Summary of Results. 
164. The investigations into the nature of the radio-active 
emanations have thus led to the following conclusions:—The radio- 
elements thorium and radium continuously produce from themselves 
radio-active emanations at a rate which is constant under all con- 
ditions. In some cases, the emanations continuously diffuse from 
the radio-active compounds into the surrounding gas; in other 
cases, the emanations are unable to escape from the material in 
which they are produced but are occluded, and can only be released 
by the action of solution or heat. 
The emanations possess all the properties of radio-active gases. 
They diffuse through gases, liquids, and porous substances, and can 
be occluded in some solids. Under varying conditions of pressure, 
volume, and temperature, the emanations distribute themselves in 
the same way and according to the same laws as does a gas. 
The emanations possess the important property of condensation 
under the influence of extreme cold, and by that means can be 
separated from the gases with which they are mixed. The radia- 
tion from the emanation is material in nature, and consists of a 
stream of positively charged particles projected with great velocity. 
Taking all these properties into consideration, it is difficult to 
avoid the conclusion that the emanations are material and exist 
in the gaseous state. The emanations possess the property of 
chemical inertness, and in this respect resemble the gases of the 
argon family. The emanations are produced in minute amount ; 
sufficient quantity has not yet been obtained to examine by 
ordinary chemical methods. With regard to their rates of dif- 
fusion, the emanations of both thorium and radium behave like 
gases of high molecular weight. 
These emanations have been detected and their properties 
investigated by the property they possess of emitting radiations of 
a special character. These radiations consist entirely of a rays, 
v.e. particles, projected with great velocity, which carry a positive 

