152 
PROCEEDINGS OF THE ACADEMY OP 
conglomerate, then an aggregate of grains of quartz cemented by calcareous 
matter. 
About sixty miles above the point where we struck the Niobrara, bed i), of 
the vertical section, is revealed to the water's edge. The dip of the strata 
towards the east gradually brings this bed to view quite conspicuously. It is 
composed of a flesh colored calcareous grit, and the eroded material of this bed 
gives to the country a dull reddish yellow tint. It also contains many layers 
of silico-calcareous concretions, forming large ledges which break into irregu- 
lar masses on exposure. The more incoherent material has much the color and 
appearance of that composing the Turtle bed at Bear creek, but contains much 
less clay. It does not differ materially from its equivalent in the White river 
valley, of which Eagle Nest Butte forms a part. 
Leaving the Niobrara river for Fort Laramie, we pass over a large area 
covered with sand hills, which have a dull ferruginous tinge, and are evidently 
composed of the eroded materials from bed D. One of these hills measured 
one hundred and eighty feet in heighth, with very steep sides, its present con- 
formation being preserved by the roots of vast numbers of a species of Yucca, 
which cover the hill and seem to find their maximum growth in this sandy soil. 
Near Spoonbill creek bed E is composed mostly of a very coarse conglomerate, 
formed of angular and water-worn fragments similar to those seen in the 
granitic, metamorphic and carboniferous rocks, in the Black Hills, the 
fragments varying in size from one-eighth of an inch, to four inches in 
diameter and cemented with rather coarse silicious sand. It kere forms huge 
overhanging ledges, large masses of which have fallen to the base of the hills, 
and are scattered over the plains below, giving to the scenery a very rugged 
appearance. 
On Raw Hide Butte creek, bed D approximates more closely in its character 
to the turtle bed B of the vertical section. On an exposed area, not more 
than eight or ten yards square, in the valley of the creek, I observed fragments 
of at least eight turtles ( Testudo nehrascensis) with a few mammalian remains 
similar to those found so abundantly in bed at Ash Grrove Spring. The 
upper Miocene beds E and D occupy the country around Fort Laramie, ex- 
clusively, and extend to the base of the Laramie range of mountains. Bed Z> 
attains by far the greatest thickness, bed having been eroded away to a great 
extent, and losing its conglomerate character, while bed D becomes one hun- 
dred and eighty to two hundred feet in thickness. The incoherent materials are 
here much more calcareous and of a finer grit, while the concretionary layers 
are formed of a sandstone coarser grained than at localities heretofore men- 
tioned. 
From Fort Laramie to Laramie Hills, August lid. 
Our course was 10° south of west from Fort Laramie ; travelled over Tertiary 
beds E and D for twelve miles, until we came to the head of Warm Spring, 
where we observed a bed of carboniferous limestone seventy-five feet in thickness. 
The strata seem to dip gently each way from a central axis, and are exposed 
at this locality over an area of only five or six hundred square yards. The up- 
heaval is evidently a local one, the limestones being revealed by the erosion 
and removal of the Tertiary beds from the valley of the stream, which are every 
where undisturbed, resting unconformably upon the limestones on all sides. 
Nine miles farther on our route, another upheaval is exposed by the wearing 
away of the Tertiary beds in the valley of the Big Cotton Wood creek. Here we 
have eighty feet of carboniferous limestone, with a similar central axis of eleva- 
tion from which the strata dip in all directions, while the Tertiary beds again 
rest unconformably upon their inclined edges. As we approach the Laramie 
Hills, no carboniferous rocks were seen in place, but the whole country is 
covered with a heavy deposit of drift, consisting of gravel and water-worn 
boulders from all the formations in this region. 
Descending the Laramie Fork toward Fort Laramie, we again find the coun- 
try covered with a thick deposit of drift, composed of a great variety of more 
[June 
