GEOLOGICAL SURVEY OF THE TERRITORIES. 77 



Sir: I have the honor to submit the following preliminary report of 

 my labors in the field, connected with the geological survey of Colorado 

 and Wyoming Territories. I beg leave to state here that these notes are 

 prepared in the field after the labors of the day are completed, far away 

 from books aud collections, and without that opportunity for mature 

 reflection which shook! characterize a final report, and therefore I ask 

 you to look with leniency on any errors that may occur, or any want of 

 precision of statement. 



My examinations properly begiu at Cheyenne City, along the line of the 

 Union Pacific Eailroad ; but the connection of the geology eastward with 

 that to the west will be better understood by a resume of the structure 

 of the country from Omaha. 



At Omaha, and extending above that point along the Missouri Eiver 

 for about 40 miles, we find the underlying rocks to belong to the Upper 

 or Barren Coal-Measures ; overlapping these are the sandstones of the 

 Cretaceous period, which first reveal themselves immediately along the 

 Missouri, about 20 miles north of Omaha, but are found about 10 miles 

 westward as much as 8 or 10 miles south of the Platte River. 



:t^ear the mouth of the Elkhorn the rusty sandstones of the Dakota 

 group occupy the whole country. Near Columbus and beyond for 20 or 

 •30 miles traces of No. 3 Cretaceous are observed, but they are never con- 

 spicuous. Numbers 4 and 5 have not been seen along the Platte. 



About 200 miles west of the Missouri Eiver, along the Platte, the light 

 clays and marls of the Tertiary period commence, foreshadowed, however, 

 by a thick superficial deposit of fine brown grit, which seems to be of 

 Post-Pliocene age, as it is filled with recent Iresh-water and land shells. 

 Helix, Planorhis, Pupa, FJujsa, &c. The Tertiary beds extend uninter- 

 ruptedly to the margin of the Laramie range, along the line of the Union 

 Pacific Eailroad. For 150 to 200 miles west of Omaha the soil is very 

 fertile, and in an agricultural j)oiut of view can hardly be surpassed ; but 

 beyond that point ,there is an absence of both wood and water, which will 

 render it impossible to cultivate the western half of the State of Nebraska 

 successfully. As a grazing country, however, it will eventually prove 

 most valuable. For sheep-raising it seems especially adapted. Sheep 

 would thrive well on the short, nutritious grasses, and the dry surface, 

 strewn with drift pebbles, would be admirably adapted to preseve their 

 feet from disease. 



It seems to me that all this portion of the West may at some period 

 be inhabited by a pastoral people, who will raise some of the finest 

 flocks and herds in America. The soil itself is fertile enough, for the 

 cuttings along the railroad show a depth of 6 to 12 inches of vegetable 

 mold, but there" are not streams enough to irrigate any great portion. 

 Even the Platte is sometimes so dry as to have no running water below 

 the junction of the forks. 



The Platte Yalley is very broad, averaging 5 to 15 miles in width, and 

 on the bottoms a good crop of grass grows every year, so that thousands 

 of tons of hay are made for the use of the Government and the Union 

 Pacific Eailroad. 



The rocks for building purposes are not abundant anywhere along the 

 Platte east of the mountains, but the materials for making bricks or 

 artificial building-stones occur in the greatest abundance, scarcely 

 equaled in any part of the world. The vast superficial or Post-Pliocene 

 deposits w^hicii cover the surface are especially adapted for these pur- 

 poses. At Sidney Station and westward there are some rather thick 

 beds of light-brown calcareous grit, which seems to answer an excellent 

 purpose for buildings, aud has been much used in the erection of round- 



