108 GHOLOG Y , 
after each flood, new strata of sand and clay are deposited, until 
the lakes and sloughs are silted up. 
When the lakes and sloughs of these bottoms are so far filled up 
as to sustain vegetable life, the decay of the annual growth, and of 
the foreign matter which falls or floats into these waters, forms a 
stratum of humus at the bottom, over the beds of clay and sand, 
previously deposited by the floods and still waters. Another over- 
flow gives another succession of sand and clay ; and the succeeding 
annual crop of vegetable matter, another stratum of humus. 
These changes have often continued until several series of these 
deposits were formed; but when the bottoms of those bodies of 
water had been thus raised so high above the river, that the floods 
thus frequently flowed into them, the deposits of sand diminished, 
and the long quiet intervals favored the deposition of clay and 
humus. In time, these shallow waters became mere marshes, where 
a rank vegetation rapidly formed thick beds of vegetable mold, for 
the support of the magnificent forests which now occupy the sites 
of those ancient lakes and sloughs. 
Such is the structure of the vast alluvial plains bordering the Mis- 
souri and Mississippi Rivers. 
The bottom of the Missouri, extending from the Iowa line to its 
mouth, is about seven hundred miles long and five broad, present- 
ing an area of 3,500 square miles; more than one-half of this, say 
2,000 square miles, may be set down as alluvium, while the river, 
‘*bottom-prairies’’ and lakes, occupy the remainder. 
On the Missouri side of the Mississippi bottom, there are about, 
4,300 square miles of alluvial bottom ofa similar character. Thus 
the alluvial bottoms of our two great rivers alone, give more than 
4,000,000 acres of land based upon these strata of sands, clays, 
marls and humus. 
And besides, the quantity is constantly increasing by the silting 
up of the slonghs and lakes, as above described. 
The soil formed upon these alluvial beds, is deep, light, and rich 
almost beyond comparison, as is abundantly proved by the immense 
burden of timber * growing upon it, and by the unparalleled crops 
of hemp, tobacco and corn, harvested from its cultivated fields. 
BOTTOM PRAIRIE. 
This important formation, in many respects, resembles that of the 
alluvial bottoms above described, with which it has usually been 
* In the fall of 1856, our surveying party measured several trees in South- 
eastern Missouri. e following measurements were obtained from some of the 
largest trees of those species :— 
In Stoddard Co., a Beach, Fagus ferruzinea, 18 feet in circumference and 100 
feet high. 
Stoddard re a Tupelo Gum, Nyssa grandidentata, 20 feet circumference 
and 120 feet high 
In Dunklin Ca, a Catalpa, Cata'pa bignonioides, to feet circumference and go 
feet high. 
In Pemiscot Co., an Elm, U/mus Americana, 22 feet circumference and 100 
feet ie 95 
ew Madrid Co., a Cypress, Zxodium distichum, 29 feet circumference 
a ae feet high 
In Cape Girardeau Co., a Sweet Gum, Liguidamibar Styraciflua, 15 feet. cir- 
rg seh 130 feet t high. 
n Cape Girardeau Co., a White Ash, Fraxinus Americana, 18 feet circum- 
coe and 110 feet hi igh. 
In Mi or Co., a Spanish Oak, Quercus falcata, 28 feet circumference and 
100 feet hig 
Bes Mississippi Co., a Sycamore, Platanus occidentalis, 43 feet in circumfer- 
ce. This Sycamore was hollow, and the cavity aeceed 15% feet in one 
paar and 13 in the pote 
confounded by geologists; though agriculturalists have made a 
distinction. 
There are, however, important differences :— 
1st. The stratification in the prairie is much more uniform, and 
more regularly extended over wide areas. 
2d. In the prairie formation, the strata are not so distinct, nor 
are they so purely silicious or argillaceous. 
3d. It was evidently formed by agencies operating over the 
entire bottoms, whose action was more uniform and quiet, and con- 
tinued uninterrupted through longer periods than those now forming 
the alluvial deposits in the same bottoms. 
4th. Where these two formations meet, one can usually trace 
out the line of demarcation. Either the strata of the prairie pass 
under those of the alluvium, or are cut off and replaced by them. 
5th. The alluvial bottom is continually increased at the expense 
of the prairie, through the action of the rivers. The current is 
constantly cutting away the prairie, forming new channels, and 
filling up the old ones with drift and silt: 
6th. No causes now in operation could, at the present level of 
the country, produce a formation of such extent and uniform struc- 
ture as the bottom prairies. 
Such are some of the facts which have convinced me that this is 
an older formation, and one entirely distinct from the alluvial bot- 
toms. Several facts show it to be distinct from, and newer than, 
the Bluff. Its composition, structure, and position, are entirely 
different, and in many places the bottom prairie rests non-conform- 
ally upon the bluff, as at St. Joseph, and the mouth of the Big 
Nemaha. 
This formation, like the last, is mide up of sands, clays, vege- 
table mould, variously interstratified. 
The sand in the upper part is fine and yellowish brown, like that 
of the Missouri sand-bars; but the lower beds are more purely 
silicious. 
The clays are usually dark, bluish-brown, and marly, with more 
or less sand and humus intermingled. 
The humus or vegetable mold has a brownish or black color ; 
when wet it is somewhat plastic, and slightly tenacious; when dry, 
it is brittle, and breaks into angular fragments, and can be easily 
reduced to an impalpable powder. These beds of humus were 
evidently formed by the growth and decay of plants in the localities 
where they are found. 
Range and Thickness. This formation is confined to the bot- 
toms of the Missouri and Mississippi Rivers, and is more abundant 
and better characterized on the former. The bottom prairie is 
about half as extensive as the alluvial bottoms above described, and 
sustains a soil of equal fertility. This estimate will give us about 
2,000,000 acres of these vastly rich savannas, all prepared by 
nature for the plow. ‘heir agricultural capacities are scarcely 
inferior to any lands in the world, as is fully demonstrated by the 
mineral contents of the strata, and the products of the numerous 
flourishing farms located upon them. 
The Organic Remains of the bottom prairie, are numerous and 
well preserved. All the shells of the bluff, save the Hedicina occulta, 
have been found in it; but no remains of the elephant or mastodon 
have yet been detected. We have collected many species of trees 
and vines from these beds. 
