188 Weed and Pirsson — Bearpaw Mountains of Montana. 













Amount 





Y2O5 taken. 



V2O5 found. 



Error. 



Amount KBr. 



H2SO4O-I) 





grm. 



grm. 



grm. 



grm. 



cm^ 



(1) 



0-1890 



0-1876 



0-0014- 



1 



10 



(2) 



0-1886 



0-1886 



0-0000 ± 



2 



10 



(3) 



0-1885 



0-1882 



0-0003- 



1 



10 



(4) 



0-1885 



0-1886 



0-0001 + 



1-5 



10 



(5) 



0-1881 



0-1873 



0-0008 — 



1-5 



10 



(6) 



0-1886 



0-1882 



0-0004 — 



2 



10 



h) 



0-3907 



0-3894 



0-0013 — 



2 



10 



(8) 



0-3907 



0-3903 



0-0004 — 



2 



10 



(f>) 



0-3907 



0-3894 



0-0013- 



2 



10 



(10) 



0-3909 



0-3889 



0-0020- 



2 



10 



(11) 



0-3911 



0-3903 



0-0008 — 



1-5 



10 



(12) 



0-3902 



0-3900 



0-0002 — 



2-5 



10 





Average error 



of series = 0-0007—. 





May, 



1896. 











Art. XXIY. — The Bearjpaw Mountains of Montana. Sec- 

 ond Paper., {Part II.) ; ^ by Walter Harvey Weed 

 and Louis V. Pirsson. 



Throughout the Bearpaw Mountains dikes of igneous rock 

 are often seen, and in certain localities they form conspicuous 

 features of the mountain slopes, weathering out as bold walls 

 of rock ; frequently, however, the ready weathering of a 

 minette-like rock, of common occurrence in the mountains, 

 makes the recognition of such dikes difficult, except where 

 contact walls of hardened shale stand in relief, or the course 

 of the dike is marked by an unusually luxuriant growth of 

 grass. 



About the Wind Butte intrusive stock the dikes possess a 

 radial disposition, and may be seen extending across country 

 for several miles. Elsewhere the observations were not com- 

 plete enough to warrant the statement that the dikes radiate 

 from igneous centers, though this seems to be the case aboui 

 the stock exposed on upper Beaver Creek. 



Most of the dikes observed were found cutting sedimentary 

 beds which they have indurated and altered near the contact, 

 but in a few instances the dikes are in the extrusive breccias, 

 and at Beaver Creek a tinguaite dike cuts the granular igneous 

 rock of the stock. 



* Published by authority of the Director of the United States Geological 

 Survey. 



