142 Prof. J. Joly on a Method of Investigating the 



are the results on certain granites treated as far as possible 

 under exactly like conditions of heating. 





Wt. Grms. 

 rock. 



Wt. Gnus. 



carbs. 



By solution 

 method. 



i 



By fusion 

 method. 1 



Granite, Ballyellin ... 



10 



25 



1-5X10" 12 



1-9X10" 12 



" " 



10 



25 



„ 



1-9 „ 



,, Glenmalure . 



10 



25 



041 „ 



1-2 



,, Killiney 



10 



25 



1-76 „ 



1-8 



„ Glencullen ... 



10 



25 



1-2 



23 







Means 



1-22 „ 



1-8 



The increase is 46 per cent, on the solution results. 



A series of experiments on basic andesites were also made. 

 It was evidently desirable to determine the calibration con- 

 stant of the electroscope for substances differing so con- 

 siderably from the granites in chemical composition. The 

 following values were obtained : — 



0*70 mgrm. uraninite, 10 grms. andesite, 25 grms. carbs. C=0*79xl0- 12 , 

 0*74 „ „ 10 „ andesitic tuff, 25 grms. carbs. 



C=0-77x 10-12. 

 0'67 mgrm. uraninite, 7 grms. Deccan trap, 28 grms. carbs. 



C=0-75x 10-12. 



As these results stand appreciably higher than those 

 obtained in the case of acid rocks 1 tried the effects of adding 

 boracic acid : — 



0'06 mgrm. uraninite, 6. grms. Deccan trap, 28 grms. carbs., 2 grms. 



boracic acid, C=0'60xl0- 12. 



The effects of the boracic acid are remarkable ; increasing 

 the fluidity and effervescence and yielding a homogeneous 

 melt. A further experiment was made with radioactive 

 material prepared in a different manner. The melt from 

 one of the experiments on the calibration constant with 

 granites was weighed in its entirety, and 3 grams of it 

 taken for admixture with 7 grams, of Deccan trap and 



