8 ON THE GEOLOGY AND NATURAL HISTORY 
CHAPTER Il. 
FROM BELLEVUE TO THE BIG SIOUX RIVER. 
After having arranged my collections for transportation to St. Louis, I proceeded to ex- 
plore that portion of Nebraska which borders on the Missouri from Bellevue to the mouth 
of Big Sioux river. Passing over an undulating country similar to that just described, 
underlaid with Carboniferous limestone, we find that Fort Lisa is the highest point on the 
river where these rocks are exposed. At Tekama, the ferruginous sandstone alone is seen 
presenting its usual lithological characters and containing much iron. ‘This entire forma- 
tion abounds with iron ore of the red hematite variety, which, if the deficiency of fuel in 
the country can be supplied from any other source, might be made of great economical 
importance. From this sandstone issue some excellent springs of water. The most im- 
portant one is Golden Spring at Central Bluffs, which yields a large supply of pure cold 
water, and will at some future period become a great resort for seekers after health and 
pleasure. 
From De Soto to Decatur, a distance of forty miles, the river bottom, on the Nebraska 
side of the Missouri, averages about five miles in width, forming a level prairie, with here 
and there a small grove of cottonwood. On the Iowa side, from Council Bluffs to Ser- 
geant’s Bluffs, a distance of one hundred miles, the bottom averages about ten miles in 
width, covered in many places with heavy bodies of timber, chiefly cottonwood, with a 
mingling to some extent of ash, elm, black walnut, &c. ‘These broad bottoms possess an 
inexhaustible fertility, as is shown by the annual growth of vegetation, which year by year 
decaying adds still more to the richness of the soil. The subsoil seems to be composed of 
calcareous and silicious marls, formed from eroded materials of the Cretaceous and Tertiary 
rocks, which have been washed down by the river and mingled together upon its bottoms. 
Above Fort Lisa the first cut banks we observed which afford a good section of the 
beds are at Wood’s Bluffs, near Decatur. 
Section of the strata in descending series : 
. Yellow Silicious marl, a recent deposit. 15 feet. 
. Yellow indurated clay, with a reddish tinge, also recent. 6 to 8 fect. 
. Heavy-bedded sandstone. 40 to 50 feet. 
. Yellow indurated clay passing down into an indurated ash-colored clay with a reddish tinge. 5 feet. 
ore © bP ee 
. Ash-colored clay with a small seam of lignite at base. 25 feet. 
No fossils were observed at this locality excepting quite uncharacteristic vegetable 
remains. But near the Blackbird Mission, eight miles above, the sandstone is quite rich 
