layers; the lower beds have sometimes mottled drab and reddish shades, often affording a pretty marble. Near the base this rock is often traversed by vermicular cavities and cells. These may be seen from Cape Girardeau to Lincoln, and in St. Charles, Warren and Montgomery Counties, thinning out in the latter.

The First Magnesian Limestone is generally a buff, open-textured, thick and even bedded limestone, breaking readily under the hammer, and affording a useful building rock. Shumard estimated its thickness in Ste. Genevieve County to be about 150 feet. In Warren County, in North Missouri, it is seventy feet thick. It is found in Ralls, Pike, Lincoln, St. Charles, Warren, Callaway and Boone. Southwesterly, it is not well marked-indeed it seems to be absent in some counties where, in regular sequence, it should be found. It occurs in Franklin, St. Louis, and southwardly to Cape Girardeau County.

Saccharoidal Sandstone is usually a bed of white friable sandstone, sometimes slightly tinged with red and brown, which is made up of globular concretions and angular fragments of limpid quartz. The formation is well developed in Lincoln, St. Charles, Warren, Montgomery, Gasconade, Franklin, St. Louis, Jefferson, Ste. Genevieve, Perry and Cape Girardeau Counties. Besides the above, it is also developed in a more attenuated form, in Callaway, Osage, Cole, Moniteau and Boone. This sandstone is probably destined to be one of the most useful rocks found in Missouri. It is generally of a very white color, and the purest sandstone found in the State, and is suitable for making the finest glassware. Its great thickness makes it inexhaustible. In St. Charles and Warren Counties it is 133 feet thick, and in Southeast Missouri over 100 feet thick.

The Second Magnesian Limestone occurs in all the river counties south of Pike as far as the swamps of Southeast Missouri, and is more often the surface rock in all the counties south of the Missouri and Osage Rivers, to within fifty miles of the western line of the State. It is generally composed of beds of earthy magnesian limestone, interstratified with shale beds and layers of white chert, with occasionally thin strata of white sandstone, and, near the lower part, thick cellular silico-magnesian limestone beds. The layers are more often of irregular thickness and not

very useful for building purposes. It is often a lead-bearing rock, and most of the lead of Cole County occurs in it. It is from 175 to 200 feet thick.

The second sandstone is usually a brown or yellowish brown, fine-grained 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 composed of thin strata of light, soft and porous, semi-pulverulent, sandy chert or hornstone, whose cavities are usually lined with limpid crystals of quartz.

The Third Magnesian Limestone. This also is an important member, occurring in nearly all the counties of Southern Missouri. It is generally a thick-bedded, coarsely crystalline bluish gray, or flesh-colored magnesian limestone, with occasional thick chert beds. It is the chief lead-bearing rock of Southeast and Southern Missouri. In some counties it is as much as 300 feet thick.

The Third Sandstone is a white, saccharoidal sandstone, made up of slightly-cohering, transparent globular and angular particles of silex. It shows but little appearance of stratification. The Fourth Magnesian Limestone.-This formation presents more permanent and uniform lithological characters than any other of the magnesian limestones. It is ordinarily a coarsegrained, crystalline magnesian limestone, grayish-buff in color, containing a few crevices filled with less indurated, siliceous matter. Its thick, uniform beds contain but little chert. The best exposures of this formation are on the Niagara and Osage Rivers.

This magnesian limestone series is very interesting, both from a scientific and an economical standpoint. It covers a large part of Southern and Southeastern Missouri, is remarkable for its numerous and important caves and springs, and comprises nearly all the vast deposits of lead, zinc, copper, cobalt, the liminite ores of iron, and nearly all the marble beds of the State. The lower part of the first magnesian limestone, the saccharoidal sandstone, the second magnesian limestone, the second sandstone, and the upper part of the third magnesian limestone be

long, without doubt, to the age of the calciferous sand rock; but the remainder of the series to the Potsdam sandstone.

AZOIC ROCKS.

Below the rocks of the silurian system there is a series of siliceous and other slates, which present no remains of organic life; we therefore refer them to the Azoic age of the geologist. They contain some of the beds of specular iron. In Pilot Knob we have a good exposition of these Azoic strata. liferous rocks rest non-conformably on these strata.

IGNEOUS AND METAMORPHIC ROCKS.

The lower fossi

Aside from the stratified rocks of Missouri, there is a series of rounded knobs and hills in St. Francois, Iron, Dent and the neighboring counties, which are composed of granite, porphyry, diorite and greenstone. These igneous and metamorphic rocks contain some of those remarkable beds of specular iron, of which Iron and Shepherd Mountains are samples. This iron ore often occurs in regular veins in the porphyry.

HISTORICAL GEOLOGY.

When the continent of North America began to emerge from the primeval ocean, Pilot Knob, Shepherd Mountain and the neighboring heights were among the first bodies of land that reared themselves above the surrounding waters. When Pilot Knob thus grew into an island, it stood alone in the ocean waste, except that to the northwest the Black Hills, to the northeast a part of the Alleghany system, and to the southwest a small cluster of rocks lifted their heads out of the flood. These islands were formed in the Azoic seas by mighty internal convulsions that forced up the porphyry and granite, the slates and iron beds of the great ore mountains of Missouri.

COAL.

The Missouri coal fields underlie an area of nearly 25,000 square miles, including about 160 square miles in St. Louis County, eight square miles in St. Charles, and some important outliers and pockets, which are mainly cannel coal, in Lincoln,

Warren and Callaway Counties. This area includes about 8,400 square miles of upper coal measures, 2,000 square miles of exposed middle, and about 14,600 square miles of exposed lower

measures.

The upper coal measures contain about four feet of coal, including two seams of one foot each in thickness, the others being thin seams or streaks.

The middle coal measures contain about seven feet of coal, including two workable seams of twenty-one and twenty-four inches, one other of one foot, that is worked under favorable circumstances, and six thin seams.

The lower measures contain about five workable seams of coal, varying in thickness from eighteen inches to four and one half feet, thin seams varying from six to eleven inches, and several minor seams and streaks, in all, thirteen feet, six inches of coal. We therefore have in Missouri, a total aggregate of twentyfour feet, six inches of coal. The thinner seams are not often mined, except in localities distant from railroad transportation.

All beds over eighteen inches thick are workable coals. The area where such may be reached within 200 feet from the surface is about 7,000 square miles. Most of the State underlaid by the coal measure is rich farming land. That underlaid by the upper measure includes the richest, which is equal to any upon the globe. The southeastern boundary of the coal measure has been traced from the mouth of the Des Moines through Clark, Lewis, Scotland, Adair, Macon, Shelby, Monroe, Audrain, Callaway, Boone, Cooper, Pettis, Benton, Henry, St. Clair, Bates, Vernon, Cedar, Dade, Barton and Jasper Counties into the Indian Territory, and every county on the northwest of this line is known to contain more or less coal. Great quantities exist in Johnson, Pettis, Lafayette, Cass, Chariton, Howard, Putnam and Audrain. Outside the coal fields, as given above, the regular coal rocks also exist in Ralls, Montgomery, Warren, St. Charles, Callaway and St. Louis, and local deposits of cannel and bituminous coal in Moniteau, Cole, Morgan, Crawford, Lincoln and Callaway. In 1865 Prof. Swallow estimated the amount of good available coal in the State, at 134,000,000,000 tons. Since then numerous other developments have been made, and that estimate is found to be far too small.

LEAD.

This mineral occurs in lodes, veins and disseminations, which are, as yet, only partially determined. Enough, however, is known of the number, extent, dip and thickness of these deposits to show that their range and richness exceed those of any other lead-bearing region in the world.

Galena occurs in this State in ferruginous clay, that becomes jointed, or separates into distinct masses, quite regular in form, when taken out and partially dried; also in regular cubes, in gravel beds, or with cherty masses in the clays associated with the same. These cubes in some localities show the action of attrition, while in others they are entirely unworn. Lead is found in the carboniferous rocks, but perhaps the greater portion is obtained from the magnesian rocks of the lower silurian, and in one or two localities galena has been discovered in the rocks of the Azoic period. At Dugals, Reynolds County, lead is found in a disseminated condition in the porphyry.

THE SOUTHEAST LEAD DISTRICT.

The Mine La Motte region was discovered about 1720 by La Motte and Renault. It was not, however, until this territory was ceded to Spain that any considerable mining for lead was done in this part of Missouri. Moses Austin, of Virginia, secured from the Spanish Government a large grant of land near Potosi, and sunk the first regular shaft; and, after taking out large quantities of lead, erected, in 1789, the first reverberatory furnace for the reduction of lead ever built in America.

In all this region are found crystallized cubes of galena in the tallow clay, occurring as float. In Franklin, Washington and Jefferson Counties galena is found in ferruginous clay and coarse gravel, often associated with small masses of brown hematite iron and the sulphuret of iron; sometimes lying in small cavities or pockets.

The Virginia mine in Franklin County has produced by far the greater portion of lead from this section.

At the Webster mines, the silicate and carbonate of zinc are found always accompanying the lead. At the Valle mines silicate of zinc and baryta occur, as well as hematite iron ore. The