CO to 
94 
ON THE GEOLOGY AND NATURAL HISTORY 
Feet. 
distributed somewhat sparingly throughout the bed of sandstone. It also contains some fine impressions 
of dicotyledonous leaves. 
. Dark indurated carbonaceous clay, . . . . . . . . . . . . . 2£ 
. Lignite, of an average degree of purity, ............ 2 
4. Indurated clay with a reddish tinge containing much carbonaceous matter, ...... 2 
5. Light yellow clay with seams of carbonaceous matter disseminated through it, a sort of fine clay, 4 feet 
exposed above the water-level. 
Thirteen miles above Fort Clark, at Fed spring, on the right side of the Missouri, are a 
long series of nearly perpendicular bluffs, exposed by the river. This is the best locality 
for the collection of fossil plants I have yet seen. They are finely preserved, occur in 
great profusion, and belong nearly all to dicotyledonous trees. The following is a vertical 
section of the different beds in descending order, as they appear in this range of hills: 
Feet. 
1. Ferruginous marl, ................ 10 
2. Variegated bands of. argillaceous grits, ............ 80 
3. Seam of impure reddish lignite, 2 inches. 
4. Yellowish gray grit, with numerous concretions, in horizontal layers, filled with beautiful impressions of 
leaves,..10 
5. Seam of lignite, 2 inches. 
6. Yellowish gray sand with argillo-calcareous concretions, laden with impressions of dicotyledonous leaves, 10 
7. Earthy lignite, 3 inches. 
8. Yellow and drab clay and sandstone, containing argillaceous concretions with vegetable impressions, . 15 
9. Dark reddish earthy lignite, 4 inches. 
10. Yellow argillaceous grit, ............... 20 
11. Alternate layers of lignite and clay varying in thickness at different localities within a distance of four 
miles,..4 to 15 
12. Heavy-bedded friable sandstone, very ferruginous, varying in color from yellow to gray and yellowish gray. 
Same bed, I think, as seen at Fort Clark and on the summit of Square hills, containing so many fossils. 
Here we have Melania Nebrascensis, Paludina multilineata, and Corbula matriformis, . . .40 
13. Seam of lignite, 2 inches. 
14. Gray argillaceous grit, ............... 4 
15. Lignite of excellent quality, .............. 2 
16. Bluish gray clay, slightly arenaceous, ............ 6 
17. Lignite near water’s edge, quite pure, . . . . . . . . . . 3 to 4 
Beneath bed 17 may be seen at low water a heavy-bedded gray sandstone. 
In speaking of lignite as of a good quality, I mean, that it contains a small amount of 
earthy material, hut I have not yet seen any of it that would be of much value for economi¬ 
cal purposes.* Specimens from this locality and from Fort Berthold, forty miles above, 
* I am satisfied that some of the beds of lignite, especially those on the Yellowstone, can be used for fuel, when 
the country is sufficiently settled to induce a demand for it. There are some excellent beds of lignite on the North 
