﻿Thorium Content of the Earth's Crust. 

 I. Acid Rocks. 



485 



Composite. 



63 G-ranit-.es 



23 Acid Intrusive & Volcanic 

 Ditto New Solution 



Bagrm. 

 per gnu 

 XlO 12 . | (1) 



Thorium grm. per 

 grm. X 10 5 . 



2-7 I 204 

 3-9 2-31 



(3_ 



2-00 



2-20 



Ratio 

 Ra/Th X 10' 



1-33 

 1-73 



Mean for 86 rocks=2-05xl0-5 



II. Intermediate Rocks. 



12 Syenites : 



(1) 10 grms. in solution 



(2) 6 grms. in solution 



(3) 5 grms. in solution.. 

 6 of the above Syenites .. 

 8 Diorites 



18 Trachytes 



10 Porphyries 



24 



4-08 



1-75 

 1-68 

 4-2 



1-6 



0-99 





30 



1-79 





2-8 



1-54 





0-59 

 1-37 

 1-47 

 0-57 

 1-62 

 1-68 

 1-82 



Mean for 48 rocks =1 '64 x 10-5 



III. Basic Rocks. 



11 Basalts (chiefly Hebridean) 



5 Gabbros 



8 Diabases and Dolerites 



14 Basalts and Melaphyres .. 



18 General Basalts 



Ditto New Solution 



0-5 



0-38 





1-3 



0-50 





1-0 



0-22 





2-0 



0-84 





1-4 



063 



063 

 0-56 



1-28 



2-6 



4-55 



2-38 



2-22 



250 



Mean for 56 rocks=0'56xl0-5 



IV. Miscellaneous Rocks. 



7 Vesuvian Lavas \ 12*6 



14 Gneisses 



6 Deccan Traps 



Globigerina Ooze 



56 per cent, soluble in HOI 

 44 per cent, insoluble ,, 



Allin one solution 



Krakatoa Ash : 



Sol. I 



Sol. II 



Sol. Ill 



12-6 



236 





2-1 



0-87 



0-47 



00 



0-281- 

 036 



0-8 

 0-9 



1 



... 



1-0 



5-34 

 242 



t This is per grin, of Globigerina Ooze. 



Note. — [a) The results given under column (1) for the thorium content 

 were obtained while working- with the higher constant, while 

 those in column (2) were obtained with the lower constant, 



(b) Krakatoa Ash. In solution Land solution 11. 2 grms. of 

 KC10 3 were added to the fusion mixture. 100 c.c. of HC1 were 

 used in solution II. instead of 50 c.c. Solution III. was made 

 in the usual way. 



