310 



Mr. C. S. Wright on Variations in the 



'screening action of the lake, minus any effect due to an 

 intrinsic radiation from the boat itself, is represented by the 

 value of 6*7 ions per c.c. per sec. with the particular lead 

 cylinder used. From the figures which are given later in 

 Table X., it will be seen that the screening effect of the lake 

 in a cylinder of lead in the condition of that used in the 

 above experiment, is represented by 9 ions per c.c. per sec, 

 which shows that approximately 2*3 ions per c.c. per sec. 

 must have been due to a radiation emitted by the steamer or 

 by its contents. 



(2) Measurements made along the Water front of Toronto Bay. 



A second series of measurements was made with the lead 

 cylinder referred to in the first portion of the paper as 

 ~No. 1, after it had reached what has been referred to above 

 as the steady condition, observations on the ionization being 

 token at different points along the water front of Toronto 

 Bay. 



The results given in Table X. show a total decrease of 

 9 ions per c.c. per sec. from the value of " q " obtained in 

 the laboratory due to the screening action of the water, and 

 they seem to indicate in addition that the ionization over 

 sandbanks washed up by the w T aves was but little greater 

 than that over water, even of a considerable depth. 



Table X. 

 Dec. 28th. — Lead Cylinder 1, in steady state. 



" <? " ^Number of ions 



per c.c. per sec. 



(mean value). 



Locality. 



1 



22 5 

 19-3 



141 



142 

 13-5 



Laboratory of new Physics 

 Building. 



Under York St. bridge — 1 

 " made land," 30 m. from 

 water. 



South end of west side of 

 Eastern Gap, 3'40 m. from 

 shore. Water 4*6 in. deep. 



Sand-spit of Ward's Island, 

 110 m. from shore. 



Toronto Canoe Clubhouse. 

 Light pine structure on 

 piles. Water 5*6 m. deep. 



