16 ROYAL SOCIETY OF CANADA 
The mean of these values is about 1.21077, and as this result 
is of the same order as that obtained by Strutt (1.4X10—1?) we did 
not think it necessary to examine a larger number of specimens. 
It will be noted that in every case the substances examined con- 
tained much more radium than that required to account for the exist- 
ing temperature gradients of the earth. It is difficult to understand 
how the earth can have remained at its present temperature when 
radium is so plentifully distributed in the constituents of the earth’s 
mass. Strutt has suggested that the interior of the earth is different 
in constitution to the earth’s crust, and the great density of the earth 
lends some weight to this suggestion. Moreover, Milne finds further 
support to this hypothesis in the rate of propagation of earthquake 
waves. However, we know so little of the conditions under the high 
temperatures and enormous pressures in the interior of the earth, that the 
question must remain speculative for the present. 
As the work of obtaining the rocks in a state of solution is some- 
what lengthy, involving the expenditure of time and materials, some 
experiments were made in order to ascertain if the emanation could 
be driven off by simple heating. Fifty grams of each specimen inves- 
tigated were powdered and passed through an 80-mesh sieve. The 
powder was placed in a porcelain tube and heated for an hour over 
a combustion furnace. The air driven out by expansion was collected 
over water, and at the end of the heating the air in the tube was blown 
out, and all the gases thus obtained were introduced into the electro- 
scope and tested. The results were compared with those obtained 
when portions of the same specimens were in a state of solution, and 
the emanation driven off by boiling. The amounts found in heating 
expressed as percentages of the amounts found by boiling are as follows: 
Per Cent. 
ren GFOnMinnrestOnies):!4 si eid) Een Le RU blue eee Weare es 27 
A DE EPA UE à FO Nisa a Pal eve ek Ret SAR A EE ake Ree ame 49 
Fées) ANA HAMMEL ter ee Piet eS RS Sa hom 10 
Nephelime syenttess ct % lio Ste NE ay 16 ey passe baie the seater oe 55 
Led clays cane ells Grease dias chet tes date avert ENS 4? 
DA MICA VA: BANU LUNA NU | UE PARTS AA aun ER RES SON 81 
It is, therefore, clear that the method does not give consistent 
or accurate results. But when a large number of rocks have to be 
examined, the extraction of the emanation by heating may serve as 
a valuable preliminary test, and furnish an indication of the amount 
of material which must be brought into solution, in order to obtain 
