OF THE UPPER MISSOURI. 95 
present the following characters on examination: contain no bitumen; sublaminated 
structure ; compact fragments have a somewhat conchoidal fracture and a jet shining black 
color; almost always reveal the vegetable fibre; ignites very slowly; burns with a light 
yellowish flame, and emits a sulphurous smell. 
Throughout the denuded portions of this formation, great quantities of silicified wood 
are found in a fine state of preservation and so close is the resemblance that it may readily 
be mistaken at a distance for recent wood. Near the foot of the Great Bend of the Mis- 
sourl, above Fort Berthold, I observed a silicified stump near the base of the bluff, standing 
upright, three feet in diameter, with a cavity in the centre 6 inches in diameter, and so 
perfectly is the original fibre preserved, that the layers of growth are as distinct as in the 
stump of a tree just felled with the axe. 
Near the Great Bend the surface of the country presents an exceedingly rugged appear- 
ance, and is called by the Indians and traders “ Les Mauvaises Terres,” or Bad Lands. 
The bluffs here afford fine examples of the spontaneous ignition of the lignite beds, by 
which the superincumbent strata are fused or heated to various degrees of compactness, 
sometimes giving the hills the appearance of an accumulation of fragments of burnt bricks. 
Oftentimes the clays and sands contiguous to the lignite beds are fused, so as to exhibit 
every variety of character, from a nearly vitreous mass to a light vesicular lava with a 
specific gravity less than water. Many of these light vesicular masses fall down to the 
edge of the river, and the current in high water carries them down, scattering them on 
sandbars and bottoms, even below St. Louis, and thus the origin of the opinion that there 
were volcanic products somewhere near the sources of the Missouri. 
Section of strata at Crow hills, about one hundred miles below Fort Union: 
Feet. 
1. Yellow and gray arenaceous marl with horizontal layers of hard concretionary rocks, containing some im- 
pressions of plants, . : : : : : . . . : ‘ 0 : : 30 to 40 
2. Impure lignite, 4 inches. 
3. Indurated clay, ferruginous, with many deep iron-rust concretions, : : : 0 : 6 . 30 
4. Reddish drab, indurated arenaceous and argillaceous grit, . 6 a : 0 6 6 : . 1d 
5. Hight inches earthy lignite. ‘Twelve inches yellow clay. Four inches earthy lignite. 
6. Yellow and yellowish gray sandstone, with irregular seams of clay. This bed contains many species of 
shells, and distinct impressions of a species of fern in a black compact clay rock, exposed, . ; . 30 
One of the most interesting portions of the country occupied by the lignite deposit is in 
the region surrounding Fort Union, not only on account of its geological peculiarities, but 
also from the number and variety of its fossils. Scattered over the denuded hills on both 
Platte, 18 inches to 2 feet in thickness, which has been used with success at a military station near it. It will 
not, however, supply sufficient heat for welding iron. 
