McCoy and Ross — Thorium Compounds. 



Table VIII. Monazite, No. 4. 



a x 



441 



E 



1-1081 



12-83 



12-27 



•0903 





•64 



•2973 



10-75 



10-64 



•0279 





•17 



•2123 



9-53 



9'48 



•0224 





•12 



•1078 



6-26 



6-24 



•0173 





(•06) 



•0526 



3-68 



3-67 



•0143 





(•03) 



w \ 



•0122 



®- 



1-7 









Table IX. 



Monazite, 



No. 5. 







tv 



«i 



a 



w 





E 



1-0590 



2-15 



J>> 



•493 



a> 



,£5 





•3174 

 •2156 

 •1375 

 •1170 



1-89 

 1-70 

 1-37 

 1-25 



"<5 ^r 



•168 

 •127 

 •100 

 •094 



o 

 IS 



s 



DQ 



*>6 



<D O) 

 c3 s 



O CD 



•0785 



•89 





■088 



o 



° 2 



•0348 



•46 



e 



•076 



o 





$;-* 



In Table X, & m represents the total activity of I s of the 

 mineral as calculated from 



iw /w. 



$ 1?7 represents the activity due to the uranium and products 

 contained in l g of the mineral. This is equal to 3280 times 

 the weight of uranium in l g of the mineral, since it has been 

 shown* that the total activity of that quantity of any thorium- 

 free mineral containing I s of uranium is 3280 units. Jc lTh is 

 the difference between k im and k lV ; it represents the total 

 activity, due to the thorium and its products, in l g of the min- 

 eral. In the last column P Th is the weight of thorium in l g 



of the mineral. -~- is as nearly constant as one could reason- 



7 Th 

 ably expect, considering that all of the errors of experiment 



are accumulated on this ratio. The radio- activity of any min- 

 eral which is sufficiently old, geologically, is therefore equal to 

 3280 Pjj + 953 P Th . 



Table X. Thorium Minerals. 



No 



Name 



%Th 



#U 



"-lni 



kiu 



hiTh 



k S Th 

 PTh 



1 



Orangite .. 



43-1 



7-76 



649 



255 



394 



914 



2 



Thorite 



46-6 



6-26 



664 



205 



459 



985 



3 



Monazite .. 



5-27 



•33 



60-2 



10-9 



49-3 



935 



4 



(i 



15-18 



•46 



164 



15 



149 



982 



5 



a 



2 - 72 



•12 



29-8 



4-0 



25-8 

 Mean = 



950 





953 



* McCoy, Phil. Mag. (6), xi, 176, 1906. 



Am. Jour. Sci. — Fourth Series, Vol. XXI, No. 126— June, 1906. 

 31 



