98 



Boltwood — Ratio of Radiu?n to Uranium . 



walls of this case were 6 mm in thickness and were grooved on 

 the edge to a depth and width of 3 mm . Two plates of plate- 

 glass 3 mn) thick fitted closely into the grooves of the case and 

 the joint was made air-tight by the use of hot sealing-wax. 

 The glass plates formed the front and back of the electroscope 

 case. The case was provided with two brass stopcocks, G, and 

 carried on the top a glass tube T, 2*5 ctn in diameter and 7*5 cm in 

 length. The gold-leaf, I, was attached to the brass plate j?, 

 which was 5 cm long and l cm wide, and was soldered to a brass 



rod l*5 cm long and 3 mm in diameter. The rod s of cast sulphur, 

 4 C(n long and l cm in diameter, served as an insulating support 

 for the gold-leaf and was attached at the top to a brass rod 

 12 cm in length and 3 mm in diameter. The brass rods were con- 

 nected firmly to the sulphur support by warming the rods to 

 above the melting point of sulphur and pushing them a short 

 distance into the ends of the sulphur rod. Fitted to the top of 

 the tube T was a brass ring, C, into which screwed the cap _B, 

 also of brass. Through the latter passed a short glass tube l cm 

 in diameter and contracted somewhat at the top. This glass 

 tube was filled with melted sulphur, which was then allowed to 

 solidify. The end of the rod t was then warmed and pushed 

 through the sulphur plug until it extended about 5 mm beyond 



