TH GHOLOGY OF THE EITTUE ROCKY MOUNTAINS: 
Tue Little Rocky Mountains resemble a wooded island, 
rising 2000 to 3000 feet above the treeless plains of central 
Montana, far from the Rocky Mountain Cordillera, whose near- 
est foothills lie 180 miles tothe west. They form a conspicu- 
ous geographic feature of a region which is generally destitute 
of any prominences or land marks for the traveler, and hence 
are appropriately called by the Indians “ Eah héa weetan’”’ or 
the Island Mountains. They are situated north of the Missouri, 
between that stream and the Milk River, sixty miles south of the 
international boundary line. The mountains are formed by a 
dome-shaped uplift exposing Archean and Paleozoic rocks, in a 
region of nearly horizontal Cretaceous strata. Occurring in this 
isolated position the uplift is of special interest, as its simplicity 
of structure and distance from the complicated disturbances of 
the Cordilleran zone make the problem a peculiarly clear one ; 
while the occurrences of the older sedimentary strata and the 
relations and nature of the igneous rocks are of unusual interest, 
constituting a needed factor for the discussion of some of the 
broader problems of general geology. 
As the mountains have never been mapped, the accompany- 
ing sketch showing the drainage and relief of the region, has 
been drawn from a few field notes, the crest line being taken from 
the plat of the survey of the boundary line of the Indian reser- 
vation. The altitudes of the main peaks are approximate, but 
the map will be found useful in locating the various points men- 
tioned in this paper. 
* Published by permission of the Director of the U. S. Geological Survey. 
The present paper is based upon notes made during a brief visit to the region in 
September 1895, to report upon the mineral resources of the reservation to the Com- 
missioners appointed to treat with the Indian tribes of the Fort Belknap reservation. 
W. H. Weed. 
399 
