[MCLENNAN] EARTHS PENETRATING RADIATION 7 
From the numbers given in the table it is evident in the first place 
that the value obtained for “q” was practically the same when the 
point of observation was taken inside either a brick or a stone struc- 
ture at points so far separated from each other as Cambridge, England, 
Bowland, Scotland and Toronto, Canada. 
In the second place from the measurements made at the Meteoro- 
logical Observatory, Toronto, it is clear that the building itself contri- 
butes in a measure to the penetrating radiation, for the readings ob- 
tained on the lawn near that building were on the average more than 
1 ion per cc. per second less than those taken inside the obser- 
vatory. 
In the third place the numbers show that all the values obtained 
for “q” on the S.S. Grampian were less than any and all of those 
obtained on land. 
Further, the mean of these readings, 6-03 ions per cc. per sec., 
agrees well with the reading obtained by Simpson and Wright! 6-3 
ions per ec. per sec. on the Terra Nova on the open sea. Moreover, as 
the value found for “q” over the water of Toronto Bay with a receiver 
of the same material as the one used in this investigation was 4-4? ions 
per ce. per sec. and as Simpson and Wright obtained 4-1 per cc. per 
sec. for “q” on a small skiff on the open sea, it would appear that the 
effective radiation from a large ship such as the Grampian is practically 
the same as that from a vessel of the size of the Terra Nova. 
A point of interest in connection with the readings taken on the 
steamer (which, however, may possibly be purely accidental) is the 
gradual drop which they show after leaving Glasgow until Sept. 21st 
was reached. The reading opposite this date is the mean of those taken 
during the day preceding the passage through the Straits of Belle 
Isle. It is higher, it will be seen, than any of those taken during the 
voyage. The reading 5-78 ions per cc. per sec., was taken when in the 
River St. Lawrence near Rimouski and the last, 5-92, ions per ce. 
per sec. as the steamer was approaching Quebec. The numbers it will 
be seen show a gradual rise during the passage up the river. 


1Simpson and Wright. Proc. Roy. Soc. Series A, Vol 85 p. 175, 1911. 
2 Loc. cit. 
Note added June 30, 1912. 
In some measurements made by the writer in collaboration with Mr. A.R. 
McLeod since the presentation of this paper in May, with the receiver used in the 
experiments described above, a value was obtained for ‘‘q” of 4-46 ions per cc. per 
sec. over the waters of Lake Ontario. In this case the observation station was a 
small platform supported by four long gas pipes driven into the sand at a point in © 
the Lake where the water was four metres deep. It is interesting to note that the 
value is practically the same as that obtained by Wright and the writer in 1909 on 
the ice over the waters of Toronto Bay. 
