224 



Transactions. 



The apparatus 

 follows : — 



used in the remaining experiments was as 



The brass rod and guard - 

 cylinder were first charged 

 as before, while the wire 

 from the guard - tube was 

 dipped into the mercury, 

 and the rod and cylinder 

 were made to share their 

 charge with the insulated 

 lower system by moment- 

 arily making connection 

 by attracting the steel 

 spring with a magnet. The 

 guard - cylinder was then 

 disconnected. In all ex- 

 periments the charge given 

 was such that the initial 

 divergence of the leaves 

 was practically the same. 



The Te Aroha deposit 

 that had given most pro- 

 mise of radio-activity in 

 the preliminary experi- 

 ments was that from No. 1 

 Spring, and through the 

 kindness of Dr. Kenny a 

 good supply of this was 

 obtained. All leaks are 

 expressed in micrometer 

 divisions per ten minutes. 

 The leak through the air 

 due to the influence of the 

 can alone was tested on 

 three successive days, the 

 leaks being as follows : — 

 First Day.—i-2, 4-7, 45, 40, 45 : average, 4-25. 

 Second Day.— 37, 42, 3-7, 3-7, 4-2 : average, 3-9. 

 Third Day.—iS, 50, 4-8, 48, 4-8 : average, 4-85. 

 On the third day, after the above experiments had been 

 carried out, the Te Aroha deposit was placed in the instrument 

 and the following leaks were observed: 11-5, U'O, 103, 103, 

 9-8, 8-7, 9-7, 90 : average, 100. Leak due to deposit only, 

 10 — 4-85 = 5- 15/ten minutes. 



Fourth Day.— The deposit being left in the meanwhile, the 

 following leaks were observed: 97, 102, 110, 107: average, 



a, Brass rod with mercury cup ; b. brass 

 guard-tube with connecting wire ; c. 

 sulphur ; d, iron-wire spring ; e, brass 

 ribbon ; /, copper-gauze cyUnder ; g, 

 tin can, 14 in. by 7 in. ; h. deposit. 



