34 BOTANICAL INFORMATION. 



shale, which form, for nearly a thousand miles, the right and 

 left banks of the Missouri River, or the hills of the river- 

 valley, spreading thence north and south, to California 

 and the country of the Hudson Bay. Vast beds of 100 to 

 200 feet depth, without any manifest change of strata below, 

 may be seen in the labyrinthian defiles, mentioned in the 

 saline region. Though these strata very frequently incline 

 towards ravines and river-valleys, still a slight north-easterly 

 general inclination is likewise apparent. Often, they are for 

 miles capped with flat conic heaps of heavy ferruginous 

 loam, strewed over with burnt bones, organic remains ; (Or- 

 thoceratites, Ammonites, fishes, reptiles), also pumice-stone 

 of white, grey, and yellow or red colours : sometimes there is 

 a layer of the sandstone between the loam and the shale. 

 Beds with escarpments, when freed from pressure, crumble 

 to heaps; when at the same time exposed to the sun, in that 

 state, they are combustible ; otherwise, they filter a brownish 

 water, strongly impregnated with salts. Thin layers of 

 impure chalk occur at great depth; cakes of crystals of 

 gypsum on the top, and of sulphuretic iron abundantly 

 throughout. The shale is dark stone-colour at first, becom- 

 ing slate-bluish afterwards ; it divides into thin laminee, with 

 an earthy fracture of brownish, afterwards ashy colour. This 

 formation includes the " Burning," or M Burnt Hills" of 

 Lewis and Clark, and vast portions, according to the state- 

 ments of the Indians and hunters, have been burning 

 for many months. Between this and the Missouri limestone 

 formations occurs, finally 



E. — A massive bed of bluish or whitish argil, as if cast 

 between the two formations. Great part of the Lower Platte 

 Valley is overlaid with it, and near the obelisk, or the " Chim- 

 ney," close to the junctions of the south and North Forks of 

 Platte, the same forms rounded aggregations. It is widely 

 spread over the surface, underlies the sands of the deserts, as 

 well as those of the Lower Platte. Mixed with the loam of 

 the river-valleys, it imparts great strength to the soil 

 and vegetation on account of its calcareous particles. The 

 same(?) argil appears again as an imbedded layer, from 30-40 



