No. 15. 6 feet.-Soft, buff, fine-grained magnesian limestone, interstratified with chert and a compact, flesh-colored silicious limestone.

No. 16. 25 feet.-Coarse, gray and buff silico-magnesian limestone, variegated by cavities filled with a white or yellowish pulverulent silicious substance, which decomposes on exposure and leaves the rock porous. It is an excellent fire-rock.

No. 17. 4 feet.-Like No. 14.

No. 18. 10 feet.-Like No. 15. Strata undulating.

No. 19. 2 feet.-Fine, compact, flesh-colored silicious limestone. No. 20. 8 feet. Hard, gray, crystalline, semi-vitreous, calcareous sandstone, with chert interspersed.

No. 21. 20 feet.-Slope to water.

2d Sandstone. This is usually a brown, or yellowish-brown, finegrained sandstone, 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-pulverulent sandy chert or horn-stone, 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 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 on 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.-2d sandstone.

:

No. 2. 80 feet. Gray and buff crystalline silico-magnesian limestone, somewhat clouded with flesh-colored spots and bluish bands. It is regularly stratified in thick beds, some of which have many cells filled with a white, pulverulent, silicious substance; while others are ferruginous and semi-oolitic. It contains very little chert.

No. 3. 50 feet. 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, and silicious.

No. 5 20 feet.-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 fleshcolor. It is distinctly stratified in beds of medium thickness.

No. 6. 50 feet.-Like No. 2.

No. 7. 30 feet-3d sandstone; crops out lower down.

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 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 large springs, and contains all the vast deposits of lead, zinc, copper, cobalt, hæmatite 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 1st 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 may prove to be Potsdam sandstone.

Igneous Rocks. There are a series of rounded knobs and hills in St. François, Iron, Dent, and the neighboring counties, which are principally made up of granite, porphyry and greenstone. These igneous rocks contain those wonderful beds of specular iron, of which Iron Mountain and Pilot Knob are samples.

These mountains of iron and igneous rocks are older than the oldest of the stratified rocks above described; as the beds of the latter rest against the sides of the former without exhibiting signs of any considerable disturbance.

THE MINERAL RESOURCES OF MISSOURI.

COAL.-Mineral coal has done much to promote the rapid progress of the present century; commerce and manufactures could not have reached their present unprecedented prosperity without its aid. And no people can expect success in those departments of human industry, unless their territory furnishes an abundance of this useful mineral. Previous to the present State Survey, it was known that coal existed in many counties of the State; but there was no definite knowledge of the continuation of workable beds over any considerable areas. But since the Geological Survey commenced, the southeastern outcrop of the Coal Measures has been traced from the mouth of the Des Moines, through Clark, Lewis, Shelby, Monroe, Audrain, Boone, Cooper, Pettis, Henry, St. Clair, Bates, and Vernon into the Indian territory; and every county on the northwest of this line is known to contain more or less coal, giving us an area of over 26,000 square miles of coal beds in that part of the State. The Geological Survey has proved the existence of vast quantities of coal in Johnston, Pettis, Lafayette, Cass, Cooper, Chariton, Howard, Boone, Saline, Putnam, Adair, Macon, Carroll, Callaway, Audrain; and it is confidently expected that the counties to the northwest will prove to be as rich when fully examined.

Outside of the coal field, as given above, the regular coal rocks also exist in Ralls, Montgomery, Callaway, St. Charles, and St. Louis; and local deposits of cannel and bituminous coal in Moniteau, Cole, Morgan, Saline, Cooper, Callaway, and probably other counties.

Workable beds of good coal exist in nearly all places where the Coal Measures are developed, as some of the best beds are near the base and must crop out on the borders of the coal-field. This is found to be the fact where examinations have been made. All of the little outliers along the borders contain more or less coal, though the strata are not more than ten or fifteen feet thick.

But exclusive of these outliers and local deposits, we have an area of 26,887 square miles of the regular Coal Measures. If the average thickness of workable coal be one foot only, it will give 26,887,000,000* tons for the whole area occupied by coal rocks.

The mining engineers of England allow 1,000,000 tons per square mile for every foot of workable coal.