41 THE ROYAL SOCIETY OF CANADA 
what Pound* found necessary to cut off all the radiations of the À 
type issuing from a sample of radium in equilibrium. 
It follows then that the wall emitted a radiation of the f type 
which produced a conductivity in the air in the zine receiver corres- 
ponding to about 1-5 ions per c.c. per second. 
From the nature of the observations it is impossible to determine 
whether this radiation was emitted directly by the wall or was a 
secondary radiation produced at the wall by the penetrating rays 
present at the surface of the earth. In either case it seems justifiable 
to conclude that a similar radiation was probably emitted by the soil 
of the lawn and contributed to the ionization obtained in the receiver 
when the observations were made there. It should be possible, however, 
to get more direct evidence of the existence of this 7 radiation from the 
soil by making observations at the surface of the pound in a clear space 
and at a point directly above in the free air about 15 metres from the 
ground. Such measurements should not involve great difficulty and it 
is hoped shortly to undertake them. Additional observations will also 
be made to see if a # type of radiation is emitted by walls generally of 
structures which are exposed to the earth’s penetrating radiation. 
III.—SuMMARY OF CONCLUSIONS. 
1. At Toronto the ionization obtained in air confined in a thin 
walled zine receiver of about 30 litres capacity on the surface of the bare 
ground of the University lawn is greater than that obtained in the same 
air on the ice in Toronto Bay by about 5-8 ions per c.c. per second. 
2. Evidence has been presented which goes to shew that this same 
difference exists at Livorno, Italy, and near Cape Town in South Africa 
between readings taken on the open sea and those taken on the 
neighbouring land. 
3. As Evef and Simpson and Wrightf have shewn that the pene- 
trating radiation over the ocean from radium and thorium in the sea 
is negligible, it follows that 5-8 ions per c.c. per second represents the 
average effect of the penetrating radiation emitted by the earth and 
any rays of the 8 type which may accompany it. | 
4. The observations at Toronto give evidence of the existence of a 
radiation of the f type accompanying the penetrating radiation from 
the soil which produced in the air in the zine receiver about 1-5 ions 
per c.c. per second. 
* Pound, Loc. cit. 
+ Loe. cit. 
t Loc. cit. 
