■42 Pirsson — Petrographie Province of Central Montana. 



as shown by Lindgren's* brief description and by specimens 

 collected by Mr. Weed, are mainly composed of feldspar por- 

 phyries similar to those of the Jndith Mountains. 



In all 58 analyses have been made and published of rocks of 

 this province, 15 by H. N. Stokes, 12 by W. F. Hillebrand, and 

 one by W. H. Melville in the laboratory of the United States 

 Geological Survey ; 16 by the author and 14 under his direction 

 by Messrs. H. W. Foote and E. B. Hurlburt in the laboratories 

 of the Sheffield Scientific School in New Haven. It is not 



Castle Mountains Magmas. 



12 3 4 5 6 7 





Si0 2 .... 







74-9 



65-9 



61-9 



56-8 



46-5 45-1 



42-5 







A1q0 3 ... 







13-6 



•7 

 •5 



16-8 

 1-6 

 1-2 



1 



7-3 

 23 

 2-4 



18-3 

 1-6 

 5-6 



10-5 15-4 



4-4 2-8 

 7-8 5-6 



12-0 

 32 

 53 







Fe a 3 ... 











FeO 











MgO 







tr 



1-5 





1-8 



3-6 



10-6 



65 



12-4 







CaO 







•6 



26 





3-2 



5-3 



9-5 



8-8 



12-1 







Na 2 







4-2 

 4-6 



4-7 5-2 4-3 

 3-1 3-8 3-3 



Little Belt Magmas. 



3-1 

 1-5 



2-8 

 2-8 



1-2 



2-7 







K 2 























8 



9 



10 



11 



12 



13 



14 



15 16 



17 



18 







Si0 2 



73-1 



69-7 



68-6 



64-9 



61-6 



62-2 



54-4 



52-3 48-3 



48-4 



49-0 







A1„0 8 -. 



14-3 



15-0 



18-1 



15-4 



15-1 



15-8 



14-3 



14-0 13-3 



11-6 



123 







Fe 2 3 .- 



5 



•8 



2-2 



2-0 



2-0 



1-8 



33 



2-8 4-4 



4-1 



2-9 







FeO 



•3 



•3 



•4 



1-6 



2-2 



2-4 



4-1 



4-4 3-2 



3-6 



5-8 







MgO .._ 



•2 



•7 



•7 



26 



3-7 



3-5 



6-1 



8-2 8'4 



12-5 



92 







CaO..._ 



1-1 



2-1 



1-4 



3-1 



4-6 



4-1 



7-7 



7-1 9-9 



7-6 



9-6 







Na 2 0... 



3-4 



3-4 



4-4 



4-2 



4-3 



3-9 



3-4 



2-8 3-3 



4-1 



22 







K 2 0_.__ 



4-9 



4-4 



49 



3-9 



4-5 



3-9 



4-2 



3-9 3-0 



3-2 



5'0 













Highwood Magmas. 















19 



20 



21 



22 



23 



24 



25 



26 



27 28 



29 



30 



31 



Si0 2 



... 655 



59-2 



58-0 



57-2 



56-4 i 



55-2 



51-9 



51-7 



49-6 47-8 



48-0 



46-0 



461 



A1 2 3 



.. 17-8 



13-8 



17-2 



18-5 



20-1 : 



L8-3 



15-8 



14-5 



14-5 13-6 



13-3 



12-2 



10-0 



Fe 2 ; 



i .. '7 



5-5 



2-5 



3-6 



1-3 



4-9 



4-1 



5-1 



3-5 4-7 



4-1 



3-9 



32 



FeO. 



... 1-1 



1-4 



1-2 



1-1 



4-4 



2-1 



3-2 



3-6 



5-5 4-5 



4-2 



4-6 



5-6 



MgO 



... 1-0 



4-8 



1-8 



•7 



•6 



1-8 



3-5 



4-6 



6-2 7'5 



7-0 



10-4 



14-7 



CaO. 



... 1-9 



56 



3-5 



23 



2-1 



3-6 



6-0 



7-0 



9-0 8-9 



9-3 



9-0 



10-5 



Na 2 



... 5-5 



3-1 



3-4 



4-5 



5-6 



4-0 



3-4 



2-9 



3-5 4-4 



35 



2-4 



1-3 



K 2 0. 



... 5-6 



4-2 



10-1 



8-6 



7'1 



6-4 



7-7 



7-6 



56 3-2 



5-0 



5-8 



5-1 























Little Rocky 



■ and 









Bearpaiv Magmas. 









Judith Mag 



mas 





32 



33 



34 



35 





36 



37 



38 





39 



40 



Si0 9 



66-2 



08-3 



575 



52-8 



51-9 



50-0 



46-5 



68-7 



576 



A1 2 ; 



16-2 



15-3 



15-4 



15-7 



20-3 



9-9 



11-8 



18-3 



17-5 



Fe 2 : 



3... 2-0 



1-9 



4-9 



3-1 



3-6 



3-5 



76 





•6 



3-5 



FeO. 





•2 



•8 



•9 



4-8 



1-2 



5-0 



4-4 





•1 



1-2 



MgO 







•8 



•5 



1-4 



50 



•2 



11-9 



4-7 





•1 



.2 



CaO. 



; 



L-3 



•9 



26 



7-6 



1-6 



8-3 



7-4 





1-0 



1-4 



Na 2 



l 



3 5 



5-5 



5-5 



3-6 



8-5 



2-4 



2-4 





4-9 



5-8 



K 2 0_ 



i 



5-8 



5 6 



9-4 



4'8 



9-8 



5-0 



8-7 





4-7 



9.2 







*This Journal, 



3d Ser. 



, vol 



• xlv, ] 



3P. 286-297, 1893. 









