44 Dr. H. E. Watson and Mr. Gostabehari Pal on 

 (ii.) Interrupter AC ; Galvanometer BD. 

 C = 02 microfarad; R=100 ohms. 



Balance undisturbed. 

 C = 0'4 microfarad; R = 100 ohms. 

 r 1 = 10 , 0ohms. r 2 = 90*0 ohms. 



^ = 100 2 -90 2 = l'90xl0 3 . 



.*. L = 0*760 millihenry. 



Victoria College, Stellenbosch, S.A. 



VI. On the Radioactivity of the Rocks of the Kolar Gold- 

 Fields. By Herbert Edmeston Watson, D.Sc. (Lond.), 

 and Gostabehari Pal, M.Sc. (Calcutta)*. 



THE Kolar Gold Fields are situated on the Mysore 

 plateau in lat. 13° N., and 50 miles east of Bangalore. 

 The present workings extend along a line about 5 miles 

 long running north and south, and several of them are 

 carried down for 4000 feet, the greatest vertical depth so far 

 reached being about 3600 feet. The "country rock" in 

 which the quartz lies consists of schists, and is apparently of 

 a very uniform nature throughout the workings. Conse- 

 quently it was thought that it might be interesting to carry 

 out some estimations of radium with a view to determining 

 whether its distribution in this homogeneous rock was 

 uniform. 



A few estimations of the radium in some of the other 

 rocks from the same locality have also been made for the 

 sake of comparison. 



The following is a description of the method used and the 

 results obtained : — 



Experimental. 

 The method used for the estimation of radium was a modi- 

 fication of Joly^s fusion method (Phil. Mag. xxii. 1911, 

 p. 134). It is perhaps not capable of quite general application, 

 but it proved very efficacious for all the rocks dealt with in 

 the present experiments. The principle consisted in the 

 fusion of the rocks with potassium hydroxide under reduced 

 pressure; and the results obtained appear to show that by 

 this means the radium emanation is liberated just as com- 

 pletely as by the higher temperatures necessitated by fusion 



* Communicated bv the Authors. 



