8 



that the route from the mouth of White river west to Fort Laramie 

 is probably practicable, and superior to that along the Niobrara ; 

 that the route from Fort Pierre to Fort Laramie is likewise superior 

 to the Niobrara route, but that the increased river transportation and 

 absence of settlements along this part of the Missouri river render 

 these routes at present inferior to those of the Platte valley; that above 

 Fort Pierre, on the navigable part of the Missouri river, there are no 

 routes leading from it to Fort Laramie or the South Pass that are as 

 advantageous as those enumerated. It is further concluded that of 

 all the routes explored the Platte valley is the best adapted for 

 locating a railroad to connect the settlements to be formed in the 

 mountains Avith those along the Missouri river; and that, as a national 

 route for a Pacific railroad, leading to the South Pass or to Bridger's 

 Pass, it is superior to any other in this latitude. These conclusions 

 appear to be fully sustained by the facts advanced in their support. 



The 4th part of the report treats of the Indian tribes, their num- 

 ber, location, &c. An approximate estimate of their strength is made, 

 and routes by which to operate against them, in the event of hostili- 

 ties, are discussed. Almost every part of the country examined is 

 practicable for the operations of cavalry; and routes practicable for 

 the wagons of a military expedition can generally be found, even in 

 the Black Hills, to such points as would be used as depots from which 

 supplies for brief periods could be furnished for military movements. 



The 5th part of Lieutenant Warren's report is a brief statement of 

 the meteorological phenomena of the country, as observed during the 

 explorations; the most prominent facts respecting which are the ex- 

 treme variableness of the phenomena of moisture and temperature — 

 tacts which confirm previous statements in regard to them. 



The report contains a catalogue of the fossils collected, with the 

 localities of the specimens, and similar lists of the plants and the col- 

 lections in the different departments of zoology. All these collections 

 were made without interfering with the more immediate, practical 

 ■objects of the explorations, and reflect credit on the labors of Lieu- 

 tenant Warren and his assistants. These collections are esteemed to 

 be of high scientific value; and among the discoveries due to the 

 labors of the expedition are the discovery of the Potsdam sandstone, 

 the oldest of the fossiliferous rocks, in the Black Hills, the first posi- 

 tive proof of the existence in America of the formation corresponding 

 to the Jurassic of Europe, and the discovery on the Niobrara of a new 

 formation of the pliocene tertiary, containing the remains of an ex- 

 tinct fauna resembling that now inhabiting Asia, from which at least 

 thirty-two distinct species of vertebrates have been described by 

 Professor Lcidy. The principal of these results have been published, 

 by permission of the department, in the proceedings of the Academy 

 of Natural Sciences of Philadelphia. Accompanying one of these 

 papers, prepared by Dr. Hayden, is a small geological map of Ne 

 braska. 



A military map of Nebraska and Dakota, on a scale of tto oiro « 

 prepared by Lieutenant Warren, and ordered to be engraved by 

 the Senate at its last session, is now ready for publication. 



