248 EXPLORATIONS ACROSS THE GREAT BASIN OF UTAH. 



The physical geography and geological structure of Central and Western Utah, 

 of the so-called Great Basin, has been investigated, and the prevalance of igneous rocks 

 there has been shown, part of which are of great age, while most of them appear to be 

 of comparatively recent origin. In its eastern portion Paleozoic formations have besides 

 been found in most of the mountain ranges; the Upper Carboniferous strata, which 

 had before been recognized at a few points, have been traced as far as 200 miles west 

 of Salt Lake; and decidedly Lower Carboniferous and Devonian strata have been recog- 

 nized there for the first time in the far-west, the latter, 1,200 miles, in a straight line, 

 from the nearest point where they have before been found In situ, as far as is known, 

 in the territory of the United States. The existence of the Silurian formation in the 

 same district has been rendered probable. In the western part of the Basin only a few 

 highly-altered stratified rocks were noticed, together with the eruptive masses. 



I have divided the whole distance in five sections, according to their distinct geolog- 



Section I. The district.of Eastern Kansas and Southeastern Nebraska, extending 

 westward from the Missouri River, as far as the older formations reach, including the 



Section II. The plains, comprising the country from the western limits of section 

 I to the foot of the Rocky Mountains. 



Section III. The district of the Rocky Mountains, including the area between Fort 

 Laramie and the South Pass, or, in other words, from the eastern foot of the Rocky 

 Mountains to the divide between the waters of the Atlantic and Pacific Oceans. 



Section IV. The Green River Basin, extending thence to the axis of the Wahsatch 

 Mountains, to the eastern rim of the Great Basin. 



Section. V. The district of Central and Western Utah, the so-called Great Basin, 

 between the "Wahsatch Mountains and the Sierra Nevada. 



In each of these sections I have given a synopsis of the surface configuration and 

 general character of the district, then a description of the geological formations therein, 

 and finally, some condensed remarks upon the economical geology. Only in section 

 V, T have changed this order somewhat, on account of the greater variety of questions 



As the organic remains of the collection have been examined by my friend, Mi- 

 Meek, who has, hi a separate report, given descriptions of them, and stated the conclu- 

 sions at which lie lias arrived by their investigation, I lurve generally avoided entering 

 into paleontological discussions. By the shortness of the time allowed for the com- 

 pletion of this report, I have been prevented from making some chemical analyses, 

 especially of coal and minerals, which would have given additional practical and 

 scientific interest to the report ; but by tests before the blow-pipe I have determined 

 the qualitative composition of some salts and minerals, mostly during our confinement 

 in the winter-quarters at Camp Floyd, which will be found in their respective places. 

 The collections, upon which our main results are based, have been deposited at the 

 Smithsonian Institution, in the museum of which they have been arranged for exhibi- 

 tion, while some duplicates have been sent to the Military Academy at West Point. 



A geohffinil itnrp „■,;,/ profi/r are in the course of construction, which will illustrate 



