Box 3, Folder 5: Typewritten Letters, 1848

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it contains some interesting fossils, the most remarkable of which is a large species of chambered shell called Orthoceratite.

The nearest quarry at which the building stone is found is at the first sawmill 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 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 own city is built of this rock. When our proposed railroads and plank roads are completed we shall have much of this stone brought to the city for building purposes. It is now chiefly used for window wells and caps. A variety found near Lockport in Illinois has almost 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 is said to extend along the west side of Green Bay into the state of Michigan. It is the lowest and oldest rock found in the eastern part of Wisconsin. What lies below it here we do not know.

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In the western part of the Territory, the soft yellow lead-bearing limestone is underlaid by a different rock called by Dr. Locks the "Blue Limestone," and is supposed to be the same age and character as that so fully developed about Cincinnati in Ohio. But this, although reported so confidently by him and Dr. Owen, 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 land 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 recognized 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 reddish or yellowish sandstone. 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 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

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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 rock that the newly discovered cave exists in Dane County; and which is supposed to be the space formerly occupied by a subterranean river. It has been penetrated about 1,000 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 everywhere lined with mud which has destroyed the beauty of the numerous stalactites (or stone icicles) and stalagmites which were found by the explorers.

The next or 13th formation, lying below the Lower Magnesian limestone, is another sandstone. It is different in some respects from that found above. It is usually more pure, being apparently an aggregation of pure clear quartz crystals without apparent cement of any kind. Upon exposure to the weather the cohesion of the particles is destroyed, and the rock crumbles into sand. Much of this sand is pure enough to make glass of the finest quality. It is supposed to be and probably is the equivalent of the Potsdam sandstone of the New York geologists, and is therefore the oldest of the fossil bearing rocks. The fossil remains of animals found in this rock may therefore be supposed to be those of the animals first created; and according to the theory of progressive development, from the lowest to the highest forms of living beings, the theory of the "vestiges of creation," we should expect to find here some of the least organized and lowest forms of animals. But instead of this we find the Lingula, the shell

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of a molluscous animal which stands high up in the seals of organized beings, having a heart and a circulation of blood; So the theory which makes man only an improved monkey, falls to the ground:

This oldest sandstone shows itself at intervals throughout the northern portion of the Territory from the Wisconsin river to Lake Superior. It is most fully developed at the place known as the "Pictured Rocks" on that great lake.

I have now gone through with all the rocks of a sedimentary character. They are so called because they are supposed to be sediment deposited from water. Those that remain to be considered are of a different character. They are called igneous or volcanic rocks from the fact of their having been melted and pushed up, as it were, from the depths of the earth.

The most recent of these rocks in Wisconsin are those which in popular language go under the general name of "trap rocks." They exist at the Falls of the St. Croix; on the upper Wisconsin; on the shores of Lake Superior and at various other places in the northern part of the Territory. In some localities they assume a columnar appearance resembling rudely the celebrated Giant's Causeway in Ireland. The rich mines of copper on Lake Superior are connected with these rocks and hence it is of peculiar importance that their character and localities should be carefully studied.

But the country in which the trap abounds has not yet been much explored. The settlements in that region are confined to the immediate valleys of the larger streams and in the immedi-

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-diate neighborhood of the sawmills; lumbering being the principal business pursued. Many very interesting and useful facts remain to be discovered as the country becomes known. A partial survey has been commenced by the United States, but no report has yet been published of the result. When this is completed, we may expect many important discoveries to be brought to light.

It only remains to notice those rocks commonly called primitive, because they are supposed to be the oldest. These are found in various places in the northern part of the Territory north of a line extending from the Falls of St. Anthony in an easterly direction by the Falls of the St. Croix, Chippeway, Wisconsin and Menomonee rivers. So little is known of the character of these rocks and their localities that I will not attempt to give you a detailed account of them. They are very different from our horizontal strata of limestone in this part of the Territory and the soil produced by their decomposition is very different being usually more sandy and sterile.

A singular and unexpected discovery has recently been made of the existence of a ridge of primitive rock, associated directly with the limestone rocks of the southern part of the Territory. Several years ago the late Mr. J.L. Thayer informed me that he had discovered what he supposed to be a locality of granite in Dodge county, near the western branch of Rock river. The thing seemed so very improbable that he scarcely believed it could be so, himself, and no further attention was given to the subject at the time. The place has recently been visited, however, by my friend, H.F. Hyer, Esq., who reports that a remarkable dyke or ridge of these rocks does actually exist there.