1869.] "^ [Has'tlen. 



above sea level. Settlements are nvimerous all along the road ; but while 

 there is very good grazing, few of the cereals will grow. 



All the rocks on the eastern slope incline at a greater or less angle ap- 

 parently towards the east. Just as we enter Silver Creek valley, we come 

 to numerous upthrusts of partially changed sandstones and conglomerates, 

 the first indications that we get along our route of the neighborhood of 

 igneous rocks. Some of the masses of rock which go to make up the 

 conglomerate are of great size, very compact and of a steel gray color, 

 and are enclosed in a gray siliceous paste ; but whether large or small, all 

 are angular. The formation looks much like that near South Boulder 

 creek, near Denver. 



Passing down the valley of Silver creek, we soon emerge into the valley 

 of the Weber. We come to the hills enclosing the coal which dip down 

 the valley at angles of from 20° to 50°, and of course the belt along which 

 the coal beds are exposed is very narrow. Five or six beds as I have be- 

 fore said, varying in thickness from a few to 15 feet, are reported. I heard 

 also that about 4 miles from Mr. Sprigg's opening, a bed of fossil oysters 

 had been seen above the coal. That these coal strata are of marine or 

 estuary character I have no doubt ; but the limited time given me for 

 their study prevented me from securing such positive evidence as is 

 desirable ; and as this formation occupies a vast area west of Fort Bridger, 

 it seems all the more important to fix its geological position. That it is 

 not older than the cretaceous we know by the occurrence of leaves of 

 deciduous trees, and the black plastic clays of No. 2, holding quantities 

 of fragments of fish-remains. 



I will now recapitulate briefly the principal geological formations along 

 the line of the Union Pacific Eailroad from Omaha to Salt Lake city. 



The Upper Coal Measure Limestones are seen at Omaha, near the- 

 water's edge, and quarried all along the Platte nearly to the Elk Horn 

 river. 



The Lower Cretaceous rusty sandstones of No. 1, overlap the Upper 

 Carboniferous limestones about four miles above the mouth of the Platte, 

 and extend to the mouth of the Loup Fork ; but the yellow marl deposit 

 or loess, conceals for the most part the underlying rocks. A fine yellowish 

 sand, of the same age, or a little less recent, overlajps the cretaceous near 

 Columbus. 



The chalky limestones of No. 3, with the characteristic Inoceramus 

 problematicus, here and there crop out, and some obscure exposures have 

 been detected in the Pawnee Reservation, 15 or 20 miles uj) the Loup Fork. 



This fine yellowish sand soon gives place to the Pliocene beds of the 

 Platte, Loup Fork and Niobrara rivers, indurated marls, sands, or sand- 

 stones, which continue on as far as the margin of the Laramie range of 

 mountains, 530 miles west of Omaha, that is, for nearly 430 miles along 

 the line of the railroad. In the grand anticlinal of the Laramie range, 

 which I have already described, they sometimes repose with a slight dis- 

 cordance on the older rocks ; sometimes, as near the Laramie peak, they 

 rest directly on the syenites, and entirely conceal, for a distance of 40 or 



