50 Radioactivity of Rocks of the Kolar Gold Fields. 



a different character to those previously dealt with, the melt 

 was in all cases treated with water and hydrochloric acid, and 

 any residue weighed to see if the decomposition had been 

 sufficiently complete. 



Table II. 



Eock. 



Radium Content 10 12 grm. 



1 Oore^um ^000 altered 



0-18 

 0-82 

 1-28 

 1-34 

 144 

 6-90 











6. Quartz containing tourmaline, same age as 5... 



The first o£ these samples was picked out from the piece o£ 

 rock used for the determination given in Table I. It differed 

 considerably from the rest of the rock, and it was thought 

 that the radium content of the two portions might not be the 

 same. As may be seen, however, the two were almost 

 identical. Samples 2, 3, and 4 were of approximately the 

 same age, and related geologically to the deepest sample 

 from the JVlysore mine. A comparison of 3 and 4 seems to 

 show that the quantity of radium does not vary greatly with 

 the gold content. The comparatively large amount of radium 

 in sample 6 did not appear to be due to the tourmaline, as a 

 determination made on a small quantity of the latter gave no 

 abnormally high result. 



One sample of water from a large spring at the bottom of 

 the Balaghat mine was also examined, both by boiling some 

 of the water and bv fusing the residue from over 2 litres 

 after it had stood for three weeks. Any radium was present 

 in such small quantities that it was practically undetectable. 



It is interesting to note that these rocks, which are pro- 

 bably some of the oldest known, contain so little radium. In 

 fact, the quantity appears to be equal to the smallest quantity 

 hitherto estimated in any rock. Also, as may be seen from 

 Table II., there appears to be some slight tendency of the 

 radium content of the rocks of this locality to increase 

 as their age diminishes; but the number of experiments 

 is not sufficient to show that this is definitely the case. 

 Dr. Smeeth has promised to secure a number of additional 



