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GEOLOGY. 
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Magnesian limestone, and in a few yards decreases in thickness 
from twenty feet to one. Where thinnest it is semi-vitreous, and 
the line of demarcation between it and the limestones is very 
distinct. 
A very large Orthoceras is found in this sandstone. 
2D MAGNESIAN LIMESTONE. 
The lithological characters of this formation are very much like 
those of the rst Magnesian limestone, above described. 
2D SANDSTONE. 
This is usually a brown or yellowish-brown, fine grained sand- 
stone, distinctly stratified in regular beds, varying from two to 
eighteen inches in thickness. The surfaces are often ripple-marked 
and micaceous. It is sometimes quite friable, though generally 
sufficiently indurated for building purposes. The upper part is 
often made up of thin strata of light, soft and porous, semi-pulver- 
ulent, sandy chert or hornstone, whose cavities are usually lined 
with limpid crystals of quartz. Fragments of these strata are very 
abundant in the soil and on the ridges, where this sandstone forms 
the surface of the rock. It sometimes becomes a pure white, fine- 
grained, soft sandstone, as on Cedar Creek, in Washington County, 
in Franklin, and other localities. 
3D MAGNESIAN LIMESTONE. 
This limestone is exposed in the high and _ picturesque bluffs of 
the Niangua, in the neighborhood of Bryce’s Spring, where the 
following strata were observed : 
No. 1. 50 feet of the 2d Sandstone. 
No. 2. 80 feet of gray and crystalline silico-magnesian lime- 
stone, somewhat clouded with flesh-colored spots and bluish bands. 
No. 3. 50 feet of blue and white ferruginous chert, interstratified 
with hard, compact, and flesh-colored silicious limestone. 
No. 4. 190 feet, like No. 2, save some beds are hard, compact, 
buff or flesh-colored silicious limestone. 
No. 5. 20 feet of light-drab, fine grained crystalline silico- 
magnesian limestone, often slightly tinged with peach-blossom, and 
beautifully clouded with darker spots and bands of the same hue 
or flesh color. It is distinctly stratified in beds of medium 
thickness. 
No. 6. 50 feet, like No. 2. 
No: 7. 30 feet of the 3d Sandstone. 
It also covers large areas in the southeast mining region. 
3D SANDSTONE. 
This is a white, Saccharoidal sandstone, made up of slightly 
cohering, transparent, globular, and angular particles of silex. It 
shows but. little appearance of stratification, yet the well-marked 
lines of deposition, like those of a Missouri sand-bar, indicate its 
formation in moving water. 
4TH MAGNESIAN LIMESTONE. 
This presents more permanent and uniform lithological characters 
than any of the other Magnesian limestones. It is usually a grayish- 
buff, coarse-grained, crystalline Magnesian limestone, containing a 
few cavities filled with less indurated silicious matter. Its thick 
uniform beds contain but little chert. The best exposures of this 
formation are on the Niangua and Osage Rivers. 
This Magnesian Limestone Series is very interesting, both in its 
scientific and economical relations. It covers a large portion of 
Southern and Southeastern Missouri, is remarkable for its extensive 
caves and springs, and contains all the vast deposits of /ead, sinc, 
copper, cobalt, ores of iron, and nearly all the marble beds of the 
State. They indeed contain a large part of all our mineral wealth. 
The lower part of the rst Magnesian limestone, the Saccharoidal 
sandstone, the 2d Magnesian limestone, the 2d Sandstone, and the 
upper part of the 3d Magnesian limestone belong, without doubt, 
to the age of the Calciferous sand-rock ; but the remainder of the 
series, to the Potsdam sandstone. 
SYSTEM VII—AZOIC ROCKS. 
Below the Silurian rocks, as above described, we find a series of 
Silicious and other slates, which contain no remains of organic 
life. These rocks therefore we refer to the so-called Azote Age. 
In Pilot Knob we have a good exposition of these Azoic Strata. 
IGNEOUS ROCKS. 
There are a series of rounded knobs and hills in St. Francois, 
Iron, Dent, and the neighboring counties, which are principally 
made up of granite, porphyry, syenite and greenstone. These 
igneous rocks contain some of those wonderful beds of Specu/ar 
fron, of which ron and Shepherd Mountains are samples. This 
iron ore often occurs in regular veins in the porphyry. 
HISTORICAL GEOLOGY. 
‘In the short space allotted me, it will be possible to give a mere 
outline only of the wonderful events, which transpired during the 
formation of the rocks above described, and the development of 
our State into its present physical condition. 
If we go back to the time when this continent began to emerge 
from the primeval ocean, the geological record will inform us that 
Pilot Knob, Shepherd Mountain, and some of the neighboring 
heights, were among the first portions of land that appeared above 
the waters. When Pilot Knob became an island, there was an 
unbroken ocean on all sides, save an island to the nortiwest, the 
top of the Black Hills, a larger cluster to’the northeast, in New 
York and Canada, and a small cluster to the southwest. 
These islands were formed in the Azoic Seas by the eruptions that 
forced up the porphyry, granite, the azoic slates and iron beds of 
Pilot Knob, and the neighboring heights. 
In the tranquil cycles which succeeded, the ocean was peopled 
with innumerable species of Mollusca, Zodphytes, and Trilobites. 
Plants too appeared in the waters. But for some reason these 
animals were not abundant in the waters about Pilot Knob. 
This is what we call the Age of Mollusks ; and in it were depos- 
ited the series of Magnesian limestones and sandstones, so largely 
developed in the southern and eastern portions of the State. In the 
middle portion of this age, mollusks, with conical shells as large as 
saw-logs, made their appearance. 
Towards the close of this age the higher portions of Southeast 
Missouri became dry land, and the surrounding waters were filled 
with vast numbers of Corals, Trilobites, bivalve, spiral and conical 
shells. At the end of the Age of Mollusks, the land emerged as 
' high up the Mississippi as Louisiana, and all that portion of the 
State colored yellow on the map, became dry land ; and the waters 
of the Pacific and the Atlantic were separated by a chain of islands 
