1891. ] NEW YORK ACADEMY OF SCIENCES. o9 
dle, and South buttes, the two latter being striking in appear- 
ance, forming steep, rugged cones, while the North Butte is 
somewhat less precipitous and covers more ground. Leaving 
the railroad survey at a point three thousand feet above the sea 
level, the prairie rises gradually some nine hundred feet in thirty 
miles. ‘There are no signs of civilized life in this whole district, 
excepting that as the hills are approached there are remains of a 
Government corral, suggestive of Indian days, and the homes of 
one or two settlers upon the head waters of the creeks appear. 
The prairie is strewn with glacial drift bowlders—-apparently 
of quite recent deposition, as they are so little embedded in the 
soil—with sharp angles and edges, consisting of porphyry and 
syenite. ‘There are no rocks in place, save here and there where 
streams have cut into the prairie; these are soft, calcareous and 
clay sandstones and shales, evidently very late Cretaceous or Ter- 
tiary. Upon reaching the most easterly butte it is seen to be 
divided into several peaks, the most southerly and most promi- 
nent being called locally ‘‘Mt. Morris.” Approaching this 
mountain the ground is thickly strewn with every kind of ig- 
neous rock—dark green basalts, phonolite, and every variety of 
feldspathic porphyry. The summit of Mt. Morris I found by 
observation to be six thousand three hundred feet above sea level 
and two thousand four hundred feet above the old Government 
stockade. The mountain mass, like that of the two other buttes, 
is a grayish porphyry containing small feldspar crystals, but 
gushed and seamed by dike after dike of trap and large crystal 
birdseye porphyry. Between these dikes are older clay slates, 
mica schists, hornblendic schists, all inelined at a sharp angle 
against the mountain, and indicating clearly the intrusive char- 
acter of the mass. 
The quartzite carries free gold in considerable quantity, and 
where crossed by mountain streams some very rich pay gravel 
is found, which, owing to the scarcity of. water, can hardly 
become available ; but I was informed that miners have carried 
it down the hill and washed it in the Cottonwood with profit. 
The decomposed and altered slates also gave evidence of gold, 
but no development had been instituted. Here and there 
along the hillside were float masses of manganese and bowlders 
of magnetic iron, but the most remarkable and interesting 
feature, geologically, is a collar of limestone surrounding the 
mountain about two-thirds of the way up. This limestone 
belt is nowhere wider than seven hundred or eight hundred feet, 
but forms a complete circle, excepting upon the southern slope, 
where it is either broken or its continuity concealed by the 
talus from the porphyry cliffs above. It is highly metamor- 
