GEOLOGICAL SURVEY OF THE TEREITORIES. 73 



divide of the Eocky Mountains, near latitude 44^°, longitude 110°, in 

 a lake, as some suppose, called Yellowstone Lake," which is about sixty 

 miles long and 10 to 20 wide. Its channel is formed in rocks similar to 

 that of the Missouri, about 400 miles of its course passing through Lig- 

 nite Tertiary beds. The character of its valley is very similar to that 

 of the Missouri. Most of the important branches of this river I have 

 alluded to in the preceding portion of this chapter. Tongue and Powder 

 Eivers, which are quite long branches, have their origin in the Big 

 Horn Mountains, their channels cutting through the different rocks 

 that surround the Big Horn range. Tongue Eiver is nearly 150 miles 

 in length, and flows for the most part through the soft yielding rocks 

 of the Lignite Tertiary. Powder Eiver is from 250 to 300 miles in length, 

 and also flows, nearly all its course, through the same Tertiary beds as 

 Tongue Eiver. 



Passing below Fort Union we observe on the right side of the Mis- 

 souri Eiver several large rivers, as Little Missouri, Big Knife, Heart, 

 Cannon Ball, Grand Moreau, and Big Cheyenne. The Little Missouri 

 receives a small portion of its waters from the Black Hills, but most of 

 its branches have their origin in the prairie. The Big Cheyenne, 

 though receiving most of its water from the Black Hills, takes its rise 

 far west of the hills, in the Tertiary beds; but, after flowing past the 

 Black Hills, wears its channel through the Cretaceous beds Nos. 4 and 

 5 of the section. The other rivers mentioned above take their rise in 

 the Lignite Tertiary beds near the eastern base of the Black Hills, and 

 flow through Lignite Tertiary rocks until very near or quite to their junc- 

 tion with the Missouri. 



The Teton Eiver takes its origin in the northwestern rim of the White 

 Eiver Tertiary basin, runs nearly east, for the most part through forma- 

 tions Nos. 4 and 5 of the Cretaceous period. It drains an area about 

 100 miles in length and 30 to 50 miles in width. The next most promi- 

 nent stream is White Eiver, which is noted for its relations to the " Bad 

 Lands," and giving name to one of the most remarkable Tertiary deposits 

 in the world. It takes its rise in the prairie, near latitude 42 J° and 

 longitude 104°, flows for a time in a northeast direction, then bends 

 around so as to enter the Missouri a little south of east near latitude 

 43° 41' and longitude 99^°. Nearly its entire course is through the 

 White Eiver Tertiary beds, and, for the greater part of the year, its waters 

 are so full of sediment that they are quite unfit for use. When they 

 stand for a time a thick scum accumulates on the surface which has 

 much the color and consistency of cream. The water itself looks much 

 like very turbid lime-water, and is very astringent to the taste. The 

 river has generally a wide open valley, tolerably well wooded and abound- 

 ing in fine grass, and has always been a private resort for the Indians. 

 The road between Forts Laramie and Pierre passes along the valley for 

 a considerable distance, through some of the most picturesque scenery 

 in the West. It has numerous branches ; the only one of importance is 

 called the South Fork, and is nearly as large and long as the main 

 stream. It drains an area about 250 miles in length and 40 to 60 in 

 breadth. 



The Mobrara Eiver is the next most important stream ; and as the 

 area drained by this stream has been the subject of much interest to the 

 inhabitants of Nebraska and Dakota, I take the liberty of quoting the 

 minute and excellent description of Lieutenant Warren : 



* The Niobrara being a stream heretofore unknown, and one in which the people of 

 Nebraska feel much interest, I shall describe it in detail. 



* Letter to Hon. G. W. Jones relative to liis exploration of Nebraska Territory, January, 18C8. 



