368 



Prof. Owens on Thorium Radiation. 



40 



30 j] 

 20 \\ 

 10 



3, Comparison of the Radiations from different Salts.— 

 Layers of the oxide, nitrate, and sulphate 5 centim. square, 

 and very approximately 1*3 millim. thick, were placed in suc- 

 cession on the lower of two parallel brass plates 5 centim. apart. 

 Each was charged to the same constant potential, 95 volts, 



Fig. 2. — Saturation Curve. 

 Thorium Oxide. Plates 5 cm. apart. 



140 160 



Volts. 



200 220 



nnd the steady conduction-current measured. The results 

 were as follows, where the current produced by the oxide is 

 arbitrarily taken as 100 : — 



Thorium oxide . . . 100 

 Thorium nitrate . . . 18*5 

 Thorium sulphate . . 17*5 



We see that the oxide is about six times as active as either 

 the nitrate or sulphate, the latter two are of approximately 

 equal activity. The degree of purity of the salts was not 

 determined. 



4. Types of Radiation. — Rontgen rays are known to be of 

 a complex nature, and Rutherford, as before stated, has found 



