38 THE ROYAL SOCIETY OF CANADA 
of the earth in Paris, and “q” = 3-5 at a height of 300 metres on the 
Eiffel Tower. 
In addition to these results some observations made by Gockel*— 
who noted a moderate decrease in the saturation current of an electro- 
scope which he carried in a balloon ascent of some 4 kilometres—seem 
to be the only ones which throw any light on the question of a diminution 
in the intensity of the penetrating radiation with the altitude. 
In order to see if such a diminution as that indicated by Eve’s 
numbers was observable at Toronto, a series of measurements was made 
at different points both on the ground and on buildings at different 
heights above the ground. 
The intensity of the penetrating radiation at different places was 
obtained by measuring with a C. T. R. Wilson electrometery{, carrying 
a compensating electrical condenser, the saturation current through a 
mass of air confined in an hermetically sealed zine receiver of about 
30 litres capacity. The zine of which the receiver was constructed was 
of the ordinary commercial variety and was not selected with any idea 
of being specially free from radioactive impurities. 
As V. E. Poundt has shown that 7 mms. of aluminium are required 
to completely absorb all the different types of ? radiation emitted by a 
sample of radium in equilibrium, it follows that the walls of the receiver 
used in these measurements were not sufficiently thick to exclude all 
radiations of the 8 type which might accompany and be possibly caused 
by the penetrating radiation. 
From observations made at Toronto at different points in the 
month of March last, selected sets of consecutive readings are given in 
Table II. 
From the table it will be seen that the value obtained for “q” in a 
room in the physical laboratory was about the same as that obtained 
in the open space on the University lawn, viz., slightly over 15 ions per 
c.c. per second. The measurements made on the ice on Toronto Bay, 
however, gave a much lower value “q” — 9-3 than those made on the 
lawn and confirmed the observations made by one of us and Mr. C. 8. 
Wright§ in 1907 and 1908 when there was found an exceptionally low 
value for “q” over the water of Lake Ontario. 
The observations made in a room in the basement of the City Hall 
it will be seen gave a mean for “q” of 16-1, while those made at the 
* Gockel, Phys. Zeit, 11, p. 280, 1910. 
t Proc. of Roy. Soc. of ante p. 85, 1908, and, Phil. Mag., Feb. 1909, p. 310. 
t Proc. of Roy. Soc. of Canada, p. 53, 1908, and Phil. Mag. 1909, Jan. p. 126. 
§ Loe. cit. 
