﻿Radium Content of Secondary Rocks. 239 



different distances from the plane of contact, show clearly the 

 gradation from a normal Quartzite in the proximity of the 

 granite to a Quartziferous Mica Schist at the point of 

 contact. 



A detectable increase on the amount of radium present in 

 the quartzite might have been reasonably inferred from the 

 increasing quantity of halo-bearing and radioactively 

 darkened biotite developed in it on approaching the granite, 

 but this was not in fact found to be the case. 



1 



Section. 



Radium in grams per gram, j 



A micaceous Quartzite, with quartz grains ^ 

 uniformly small and Biotite uniformly )■ 

 distributed. Poor cleavage. ) 



O6xl0-i-\ 



A micaceous Quartzite, quartz grains larger, ^ 

 more Biotite developed in parallel bands, \ 

 with some balos. ) 



0-8x10-12, 



A Mica Schist, much Biotite developed in j 

 bands. H dos plentiful. Cleavage well de- 1 

 velopecl along Joliation planes. Abundant f 

 granular Quartz, arranged in streams. \ 



0-7X1U-12. 







As far as the evidence in the case of these experiments 

 goes, there is no abnormal amount of radium which would 

 give rise to measurable effect due to the close proximity of 

 the invading granite-mass. 



A somewhat similar experiment was made in the 

 examination of a stratum of Cretaceous Chalk from 

 Carrickfergus, in thickness about one inch, caught between 

 two sills of basalt, rendered crystalline, and iron stained, by 

 their action. 



Rock. 



Radium 

 in grs. per gr. 



Cbalk (rendered crystalline) 



0-4x10-12. 



0-4 



0-7 



Same, anotber estimation 



Basalt Sills enclosing Cbalk 





Tt will be seen that in spite of having experienced extreme 

 metamorphism, the figure obtained for the chalk does not 

 measurably differ from the result (0*3) obtained on the 



