﻿196 Mr. A. S. Eve on the Radioactive Matter 



of further verification by experiments, some of which I hope 

 to undertake. For example, an electroscope well screened 

 from the earth, vertically and obliquely, should show a greater 

 decrease of ionization than one equally well screened from 

 the atmosphere. Again, the penetrating radiation in a deep 

 mine or well should be stronger than on the surface of the 

 earth. Such experiments on penetrating radiation should be 

 made out of doors, because the walls of a building made of 

 brick or stone may contribute almost as much radiation as 

 they absorb*. 



As the matter stands at present the active matter in the earth 

 seems to be the probable and sufficient cause of penetrating 

 radiation. It should be added that experiments have been 

 made by the writer with Ebert's apparatus at Montreal, and 

 the average number of ions measured in the atmosphere 

 indicate that the conditions at Montreal are normal and 

 resemble those found over a large area in Europe. 



Activity of Metals. 



In the course of these investigations the " natural leak 

 of each vessel was determined before any radioactive matter 

 was brought near them. The value of q was found from the 

 relation 



V 



where q is the number of ions produced per c.c. per second in 

 the volume S, due to whatever causes ; e is the ionic charge 

 (3*4 x 10 -10 ) : C is the capacity and Y the fall of potential in 

 time t. 



In most cases it was necessary to let the vessels remain 

 for one or two days after filling them with fresh air, before 

 a minimum value could be obtained. The cause of this initial 

 decrease has not been determined, but it has been previously 

 observed by McLennan and others. It cannot well be 

 attributed to fine dust, for I have found that tobacco smoke 

 introduced into an electroscope produces an opposite effect. 



The electroscopes were frequently interchanged between 

 one vessel and another, so as to compare the natural leak due to 

 one metal with that due to another, simply by measurement 

 of the rate of fall of the gold-leaf of the electroscope, and 

 apart from all calculations. The results were confirmed by 

 repeated observations lasting for some months, but they are 



* Observations of the penetrating radiation at the top of the Eiffel 

 Tower and in a deep mine would throw much light on this subject. 



