NATURAL SCIENCES OF PHILADELPHIA 
153 
or less water-worn materials derived from the mountains. The true Tertiary- 
beds are revealed, by erosion, occasionally near the bed of the river, but no 
indications of the upheaval of the carboniferous rocks. 
x\bout twelve miles above Fort Laramie, both on the Laramie river, and the 
Platte a remarkable deposit is seen, composed of a coarse conglomerate, fifty 
to one hundred and fifty feet in thickness, of a recent character, and evidently 
formed since the scooping out of the present river valleys. Indeed the form of 
the deposit is that of a basin twUve or fifteen miles in length, and reaching its 
greatest thickness only in the valleys of the rivers, while the more elevated 
portions of the country between the Forks consist of the true Tertiary beds. It 
seems to vary from an aggregation of particles of quartz to an exceed- 
ingly coarse conglomerate made up of every variety of material, much of which 
I have not yet seen in place. 
Fort Laramie to the Black Hills. 
Proceeding north from Fort Laramie, we pass over Tertiary beds for the first 
seven miles, and then come to an extension of the Laramie range of Hills, 
which exhibits many peculiarities. The whole range appears to be composed 
of a group of conical elevations, and ridges which seem to illustrate very clearly, 
the irregular efi"ect of the subterranean forces by which they were upheaved. 
A considerable thickness of carboniferous limestone was observed upon the 
sides and summits of these elevations, inclining at various angles, depending 
upon the power of the disturbing force from beneath, and when unchanged by- 
heat contain numerous fossils. We can here see every variety of carboniferous 
limestone, from the unchanged fossiliferous rock, to that of a completely meta- 
morphosed character, with the indications of stratification nearly or quite ob- 
literated. Sometimes the melted material is thrust up through fissures in the 
unchanged rock, so that in a single hand specimen we have the changed and 
unchanged rock. The metamorphosed carboniferous limestones are usually of 
a deep red color, very compact, sometimes assuming a vitreous aspect, ^ but 
never the thoroughly crystalline character of the older azoic rocks. Sometimes 
the limestones are elevated, so as to leave the strata horizontal, then again 
they are inclined at an angle of ten to thirty degrees. At tlie base of these 
ridges, the upper Miocene beds are seen insinuating themselves into ravines, 
or deposited high up on the sides of the elevations, thus filling up the irregulari- 
ties formed by the numerous local disturbances. 
In all cases the Tertiary beds are undisturbed, and not unfrequently rest 
directly upon the vertical edges of the azoic or granitic rocks. About eight 
miles west of Raw Hide Peak, the carboniferous limestones present a peculiar 
appearance, not unlike that of some Tertiary strata upon the Yellowstone, 
which have been fused or semi-fused by the burning out of the Lignite beds. 
The fused masses are very compact and heavy, varying in composition and 
color, red, yellow and mottled, oftentimes containing small fragments of par- 
tially changed rock, thus forming a sort of breccia. 
After crossing the Niobrara river, the upheavals nearly cease, the blue car- 
boniferous limestone only being exposed in a few places. The Tertiary beds 
occupy the larger portion of the country. Passing the dividing ridge, between 
the Niobrara and Shyenne rivers, into the Valley of Old Woman's creek, we 
find the Tertiary attaining its full development, and assuming a variety of fan- 
tastic forms from erosion, like the Bad Lands at Ash Grove Spring. The hills 
were covered with small pines. 
On the east side of Old Woman's creek is a high ridge, trending southwest 
and southeast, composed of variegated sandstone, varying from a fine compact 
silicious rock to a coarse reddish conglomerate or sandstone, with no fossils, 
except indistinct traces of vegetable remains. This ridge, which belongs to 
Cretaceous formation No. 1, is the result of a less violent upheaval, and is ex- 
posed by the erosion of the Tertiary beds from the valley. On the distant hills, 
on each side of the valley, the denuded Tertiary beds are visible, while near 
the bottom of the stream the Titanotherium bed was observed by Lieut. War- 
1858.] 
