Box 15, Folder 3: Geology of Wisconsin 1869

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mostly supplied from these quarries. The porous nature of the stone enables the heat more readily to penetrate it, and thus it is better calcined, and with less expense of time and fuel, than stone that is more compact.

The rock abounds in "fossil organic remains of a former world"; of a marine character. Many very interesting specimens of corals, shells, and trilobites, are found at these quarries. Among them the Chain coral (Catenipora escharoides) the Pentameras oblongus a trilobite resembling Triasthus Beckii, and another, the head of which bears a very strong resemblance to the human skull in form.

The same kind of rock is found at some other places. It is extensively quarried near Chicago in Illinois; and traces of it exist at Eagle Prairie in Waukesha county and at other localities in the Territory.

The lower portion of this [rock] limestone (or perhaps it should be classed by itself as a distinct rock) is of a different character, being softer, more completely filled with minute cavities, and it contains besides lime, a considerable proportion of carbonate of Magnesia. Hence it has been called Magnesian limestone. Sulphate of magnesia or Epsom salts may be manufactured from this rock. It is full of large crevices or veins, sometimes filled with clay and fragments of rock. It is found along Root river from its mouth upwards; and it again appears at the Menomonee Falls, and at Grafton in Washington county; thus making a [another] kind of semi-circle around Milwaukee. It dips towards Lake Michigan and sinks below

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the other limestones I have just described.

This is the same rock, that in the counties of Iowa, LaFayette and Grant, affords the inexhaustable vein of lead ore. Veins of copper ore are also found in it. Why it should be so abundantly supplied with metaliferous veins there, and not at other points, is difficult [I am unable] to determine. There is, no doubt, some good reason for it, but it is not found out yet. These veins do not extend very deep into the earth. Time would not allow me to enter upon a very full description of the Lead mines, and of the geological features of the country in which they are found. This portion of our Territory was examined very minutely some years ago by Dr D.D. Owen who has made a very valuable report in relation to it.

This yellowish porous limestone in the lead region forms the surface rock over a great extent of country, and has a strong dip or inclination towards the south. In Illinois it disappears [towards] near the mouth of Rock river where it passes under the coal formation. Towards the north it crops out in the bluffs on the south side of the Wisconsin river.

The limestone formations just described are very extensive, occupying the surface of large portions, not only of Wisconsin, but also of Illinois, Michigan, Indiana, and Ohio. It is named by Dr. Locke "Cliff Limestone", because it is found forming steep naked cliffs in some places. The soil resulting from their decomposition is good; and this shows the reason why the Wisconsin lead mine country, is at the same time a rich agricultural country. It is not often that

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valuable mines of metaliferous minerals are found associated with limestone as they are here. They are usually connected with primitive or trap rocks which do not always furnish the best kinds of soil.

Next below the soft porous limestone in the eastern portions of Wisconsin, is found a white, very pure limestone, disposed in regular layers, and thus affording a building material of great value. It contains some interesting fossils, the most remarkable of which is a large species of chambered shell called Orthoceratite.

The nearest quarry at which this building stone is found is at the first saw mill on the Menomonee river; it there forms the bed of the stream and is only 33 feet above the level of Lake Michigan. As we proceed westward it gradually rises until it disappears [near] in the western part of Waukesha County. At the village of Waukesha it is found in the hills at an elevation of 250 feet above the lake. It is here quarried pretty extensively, for building purposes, and the houses made from it are very pretty in appearance. It is more exposed to the weather, and has become much whiter, than at the quarry on the Menomonee. One of the large flouring mills on the water power in our city is built of this rock. When our proposed rail road and plank roads are completed we shall have much of this stone brought to our city for building purposes. It is now chiefly used for window sills and caps. A variety found near Lockport in Illinois has almost

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precisely the color of our Milwaukee brick. By importing stone from Lockport and brick from Milwaukee, the people of Chicago are able to build some handsome houses.

From the accounts of persons who have visited the places it is probable that this is the rock that forms the rapids of the Neenah river below Lake Winnebago; and it is said to extend along the west side of Green Bay into the state of Michigan. It is the lowest, and oldest rock in the series found in the eastern part of Wisconsin. What lies below it here, we do not know.

In the western part of the Territory, the soft yellow lead bearing limestone is underlaid by a different rock called by Dr. Locke the "Blue Limestone" and is supposed to be the same in age and character as that so fully developed about Cincinnati in Ohio. But this, although reported so confidently by him, and Dr. Owens is not quite certain. It is useful as a building material and affords many interesting petrifactions of shells and other marine animals. It is important in the mineral region as showing the bottom of the lead veins. When the miner has penetrated to the surface of the "Blue Limestone", his work is stopped; no more lead is to be found in that direction. The rock appears to thin out towards the north so that it is scarcely recognzed on the Wisconsin, but gradually thickens towards the south. The same rock is said to exist about the head of Green Bay, but it has not been found in this part of Wisconsin, unless the Waukesha building stone may be considered

as the same formation in a modified condition.

Next below the blue limestone in the mineral region is a layer of redish or yellowish sand=stone. On Sugar river about 15 miles from Madison this rock appears in bold cliffs. The state house at Madison is built of this sandstone. No fossils have-as of yet been found in it, so that it cannot be decided with certainty as to its proper place in the scale of geological formations, nor its age.

Below this sandstone is another yellowish limestone, quite similar in its appearance to the lead bearing rock. Dr. Owen, for want of a better name called it the Lower Magnesian limestone. It affords no lead, and does not appear to possess any useful qualities whatever. Its soft, easily decomposable nature causes it to be rapidly worn away by water percolating through it. It is in this rack that the newly discovered cave exists in Dane County; and which is supposed to be the space formerly occupied by a subteranean river. It has been penetrated about 1000 feet and appears to have numerous ramifications, so that it must be dangerous to explore it, for fear of being lost in its labyrinths. It is every where lined with mud, which has destroyed the beauty of the numerous stalactites, (or stone icicles) and stalagmites which were found by the explorers.