Читать книгу Memoirs of Milwaukee County, Volume 1 - Jerome A. Watrous - Страница 5

GEOLOGY — TOPOGRAPHY — SOIL — CLIMATE — FAUNA — FLORA.

In writing a chapter on the natural features of Milwaukee county we shall necessarily be confined to a brief outline of such general principles of geology as may be of interest or profit to the general reader, and avoid the use of such technical terms and details as may be omitted without sacrificing the subject too greatly. For a work at once elaborate and instructive we shall refer the reader to "Geology of Wisconsin — Survey of 1873-79," published under the direction of the Chief Geologist, and under authority from the state government.

Geology treats of the earth's formation and structure, its rocks, strata, minerals, organic remains, the changes it has undergone from inundation, also from volcanic and other influences. Geology is a history of the earth built upon circumstantial evidence, such as is read from the rocks, minerals and organic remains, together with stratigraphical construction, and the later disarrangement of that by volcanic action, and the slow process of erosion, which has been going on for countless ages. It is a well-established fact, the result of scientific research, that the whole country about this region has at some time, ages ago, been covered with water of unknown depth, and that these waters were constantly changing as if in motion, or by undercurrents, tides and waves. In the course of ages these waters receded, having found some outlet into the vast bodies of water that now so largely cover the earth's surface. Again, the labors of those who, during the last two hundred years, have devoted themselves to the study of the structure of the globe, have resulted in the creation of the science of geology, and the claim which this department of human knowledge has to science depends upon the symmetry which has been found to prevail in the arrangement of the materials forming the earth's crust. By the slow process of adding fact to fact and by comparing the observations of the devotees of the science in different lands it has been found that the rocky strata of the earth hold definite relation to each other in position, and hence in age; that many of them are distinguished by constant or general features and contain characteristic or peculiar remains of plants or animals by which they may be recognized wherever found. This sequence of deposit forms what has been aptly termed the geological column.

The indurated rocks, being everywhere covered with a heavy bed of drift, have been reached in this county only by boring, and this only at a few places. A well drilled in the city of Milwaukee, after traversing 170 feet of drift, met the Niagara limestone, with a thickness of 267 feet, and underlaid by the Cincinnati shale with a thickness of 165 feet. Beneath the Cincinnati shale were the Trenton and Galena limestones with a thickness of 253 feet, and these rested upon St. Peters sandstone, into which the well was drilled to a depth of 193 feet. The surface of the well is about ten feet above Lake Michigan, which shows that at that point the Niagara limestone lies 160 feet below the surface of the lake. Comparing this again with wells in other localities it appears that the strata of limestone dip to the eastward.

The geology of the soil is independent of the underlying rocks, and is referable exclusively to the drift; for, as before stated, the bedded rocks of Milwaukee county are covered with a heavy sheet of drift to a depth averaging more than 150 feet. Long after Milwaukee county was raised above the sea as a sort of plain, topped by the ocean-rippled shales of Niagara limestone; long after the depressions and uprisings that accompanied the deposit of the carboniferous or coal-bearing rocks to the eastward; and long after the streams of that ancient time had cut away the rocks to form the valleys nearly as they are today; throughout a period of erosion, when the Alleghany Mountains were reduced from a height of five miles to something near their present modest altitude — after all this the ice age came and covered the greater part of Wisconsin with a glacier sheet which completely enveloped what is now Milwaukee county. This county, therefore, has the same glacial history as has all the eastern and southern parts of the state. Not a summit is there that stood above the glaciers, and the clay and boulders that mark the drift overlie all the ordinary high land of the county. The areas covered by the drift furnish far more varied and fruitful soils than the native rocks, and hence the lands in Milwaukee county take their place among the best lands in the state of Wisconsin.

In the vicinity of Mud Creek there is a small area of rock referred, somewhat doubtfully, to what is known as the Lower Helderbergperiod. The rock is a hard, brittle, light-gray, magnesian limestone, distinguished by numerous minute, angular cavities, that give it a very peculiar porous structure. It is thin-bedded and laminated, by virtue of which it splits readily into flags and thin plates. Some layers exhibit an alteration of gray and dark-colored liminae peculiarly characteristic of this formation. The rock is closely associated with the Niagara limestone, in a depression of which it appears to lie, and it is overlain by rock of the Middle Devonian age.

This last mentioned rock is the uppermost and newest of the indurated formations of Wisconsin; it is the only representative of the Devonian age, and it is known as the Hamilton cement rock. It is found near the city of Milwaukee and occupies a limited area, lying adjacent to the lake, immediately north of the city, and rests in part upon the shaly limestone above described, and apparently upon the Niagara limestone in other portions. In general lithological characteristics it consists of a bluish gray or ash-colored, impure dolomite, which weathers upon exposure to a yellowish or buff color, owing to the oxidation of the iron which constitutes one of its ingredients. The impurities consist chiefly of silica and alumina. The rock is characterized in certain portions by the occasional presence of cavities, in which occur crystals of iron pyrites and calcite, and, very rarely, zinc blende. Crystals of the two former minerals are disseminated more or less through certain portions of the rock. In texture it is somewhat varying, being quite homogeneous in some layers and quite irregular and lumpy in others, while the chemical composition changes much less markedly though sufficiently to affect the hydraulic properties of the rock. In degree of induration it ranges from rather soft to moderately hard. The beds are usually thick, with the exception of some portions, which are somewhat shaly.

In relation to organic remains the Hamilton period marked a new era in the history of the life of the Wisconsin formations. While multitudes of Protozoans, Radiates, Mollusks and Articulates lived in the seas of the Silurian age and left their remains embedded and embalmed in the accumulating sediments, whether of sandstone, shale or limestone, no fragment or trace of a Vertebrate has been found. The Hamilton period witnessed the introduction of this highest type of the animal kingdom into the Wisconsin series. The vertebrate remains of this formation are confined to the relics of fishes, but unfortunately these are fragmentary and imperfect. They have been submitted to the inspection of eminent authority in such matters and have been found to be a new and unknown species.

The most extensive and important outcrop of this formation, known as the Hamilton Cement Rock, is found along the Milwaukee river in the vicinity of the Washington street bridge, extending above and below in sections 4 and 5, town 7, range 22 east. The rock nowhere rises to any considerable height above the river-bed, so that no extensive vertical section can be seen, and the frequent interruptions of the exposure, as traced along the river, prevent any trustworthy correlation of the strata. The lithological characters of the rock at this point are essentially those before given as general characteristics, and this locality may be regarded as the typical one of the formation. A portion of the layers found west of the bridge are more shaly than the average rock of the formation, and upon exposure tend to disintegrate somewhat more readily. A stratum found below the bridge possesses a more granular character than the rest of the formation, but the chemical analyses that have been made of the several portions indicate that these variations are largely of a physical nature, and that the chemical composition is less varying. In the drift lying upon this rock an abundance of black shale is present in thin, fragile, more or less rounded chips, indicating the near presence of the formation from which they are derived, and which may be conjectured to be the overlying black slate so abundant in other regions. The fishes mentioned in a foregoing paragraph have been found in this locality, together with a long list of invertebrates, which indicates a rich and abundant fauna. For the names and description of the fossils found in this region we would refer those interested to Volume IV of the "Geology of Wisconsin — Survey of 1873-1877," to which the writer is indebted for a great deal of the information contained in this chapter.

In section 11, town of Granville, a railroad cut just south of the station known as Brown Deer exhibits a few feet of this formation. The original lithological characters are essentially those already referred to, but the rock of this locality has been more extensively weathered than that near Washington Street bridge, and presents a buff color, except in the interior of some of the heavier layers, and it is also somewhat decomposed in certain portions. In sections 9 and 10 of the same township occurs another exposure of this formation, occupying the brow of a hill, and underlaid by limestone belonging to the Niagara formation. The rock here is a rather soft, granular, buff, impure, dolomite, much stained with iron, which is doubtless due to the decomposition and oxidation of pyrites, originally disseminated through it. Along the lake shore on Whitefish bay the formation rises slightly above the water level in a very limited exposure. The strata at this point have a firmer texture, but more uneven structure than at the previously named localities. The lines of deposition and bedding are irregular, and angular cavities of moderate size are not infrequent, some of which are filled with a semi-fluid, tar-like bitumen. An analysis of this rock shows it to' have much less silica and alumina than the beds on the Milwaukee river. The extent of this deposit in Milwaukee county is abundantly sufficient for all anticipated wants and its location is convenient and accessible, so that it forms one of the important resources of this vicinity.

By far the most important resource springing from the drift in this region has already received consideration — the fertile and enduring soils. The powdering and commingling of such a vast variety of minerals by the glacial forces was a process than which none could be better suited to produce a secure and permanent foundation for agricultural industries — a resource that is the basis of all wealth and prosperity. But second only to this in importance are the building materials furnished by the drift formation, prominent among which are the deposits of brick clay. These belong to two classes, the light colored and red clays. The former, found extensively in Milwaukee county, are lacustrine or fluviatile deposits, derived from the wash and redeposit of the bowlder clay, and occur within the area covered by that formation. A portion of these clays burn to a beautiful cream color, and their superiority in texture as well as color makes them a general favorite in the market. It is thought to be entirely safe to say that in quantity, quality, convenience of situation and facilities for shipment the Milwaukee clays are unsurpassed on this continent. The superiority of the brick is universally acknowledged, and their beauty is a matter of general commendation. The product has the light cream dolor, so long known in the market as the characteristic of "Milwaukee brick." and they are made from a light colored clay, a modified form of the glacial deposit.

When Eastern Wisconsin first emerged from the ocean it doubtless presented an essentially plane surface, having a slight inclination to the east and southeast. The irregularities which it now presents are due, in a large measure, to three different agents, acting at different times and under different conditions. These are:

1st. During that long cycle of time that existed between the emergence of the land from its bed in the vasty deep, and what is known as the drift period, the numerous streams and rivers were ploughing their beds deeper and -deeper into the primeval rocks, and rendering the former level surface more and more irregular. The softer rocks being more readily eroded than the harder ones, increased. their unevenness, there being a constant tendency of the streams to follow the softer strata wherever the slope of the land favored, and as these run in a northerly and southerly direction generally throughout this region, the main streams had, that general course. The little streams gathered into the larger ones in a manner not unlike the branches of the forest tree as they gather into the parent stem. The erosion of this nature produced in the unevenness of the surface a symmetry and a certain system easily recognizable. As this action upon the rocks occupied the period preceding the glaciers, we, for convenience, call it the pre-glacial. In Milwaukee county, however, these pre-glacial features have become wholly obscured, except in their grander outlines, by the glacial deposits, which cover this section of the state.

2nd. The modifications of the surface constituting the first class of topographical features were produced by running water; those of the second class, which follow next in order of time, were formed by ice in the form of glaciers and by the various agencies brought into action by their melting. The work of the ice was twofold; first, in the partial leveling of the surface by planing off the hills and strewing the finely pulverized rock upon the surface of the valleys; second, in the creation of a new, uneven surface by the promiscuous heaping up of the clay, sand, boulders and gravel, thus giving the land a new aspect. Among the features produced by this movement of gigantic mountains of ice are parallel ridges, sometimes many miles in length, having the same general direction as the ice movement; hills of a rounded, flowing contour, like many found along the shores of the Milwaukee river; half-embosomed rocky ledges cropping out of the hillsides, like giant battlements on titanic castles; all of which combine to form a peculiar and distinctive contour of surface easily recognizable. As all of these apparent freaks of nature are due to the action of the ice, they are denominated glacial features.

3rd. Subsequent to the subsidence of the glacial periods the streams resumed their wearing action, but under different conditions, and carved out a new surface contour, the features of which may be termed post-glacial or drift. In addition to this there occurred a depression of the land, attended by an increased volume of water in the lakes, by which doubtless all of Milwaukee county was submerged. The advancing waters leveled down many of the surface irregularities, and while the land was submerged the "red clay" was deposited, thus still further leveling the surface. After the land again rose from the water the streams resumed their cutting, and as the clay was soft, they rapidly eroded the gorges which are now extant.

To the three agencies, lake action, ice and running water, assisted slightly by winds, the topographical features of Milwaukee county are chiefly due. There is no evidence of violent eruptions, upheavals or outbursts. There was the gradual elevation and depression of the surface and probably some little flexure of the crust, but in general the region has been free from violent agitation, and owes none of its salient topographical features to such causes. Properly speaking, the county cannot be said to be hilly, nor does it sink to a dead level over any considerable area. It presents the golden mean in a gently undulating, diversified surface, readily traversable in all directions by the various highways of communication.

The features of topography of Milwaukee county are the rivers and smaller streams that traverse it, making it a well-watered district, and a gentle undulating surface, a number of eminences rising above the general level. The largest stream is the Milwaukee river, while second only in size is the Menominee river, which unites its waters with the Milwaukee, and then uniting with the Kinnickinnick, the three streams flow together into Lake Michigan at the city of Milwaukee. The southern portion of the county is well drained by Duck and Root rivers and Oak creek. The course of the Milwaukee river is decidedly interesting. It originates chiefly in Fond du Lac and Sheboygan counties from a number of nearly parallel southward-flowing streams, which gradually unite to form the main river. At West Bend, Washington county, it turns abruptly eastward. After passing Newburg it makes a rude sigmoid flexure to the north and resumes its eastward course. When within about nine miles of the lake it bends suddenly to the right and flows almost directly south parallel to the lake shore for more than thirty miles, being distant from it at some points in its course less than two miles. Near the great bend in the town of Fredonia, Ozaukee county, the stream reaches an ancient beach line, which marks the shore of the lake at the time of the deposit of the lower red clay, heretofore mentioned. The river follows along this beach line to its mouth at Milwaukee.

The Menominee river rises in the southern part of Washington county and running in a southeasterly direction through the towns of Granville and Wauwatosa, enters the Milwaukee river within the city limits of Milwaukee. It is a fine little stream and afforded many valuable pioneer mill privileges, several of which were improved. Several limestone quarries were opened along its banks, which are usually high. It receives a branch in the town of Granville, called the "East Branch," and above that point the valley is much contracted in width, there being no bottom lands on either side. Below the East Branch the level or bottom lands are usually about a half-mile in width.

The general slope of the surface of the county is to the east and south and is quite moderate. The lowest land is in the town of Lake, at the west line of section 8, near the Kinnickinnick river, where the surface lies but ten feet above the level of Lake Michigan, or 588 feet above the level of the sea; while in the northwest corner of section 30, in Greenfield township, the altitude reached is 843 feet above sea level. The remainder of the surface of the county varies in altitude between these two extremes. It should be mentioned in this connection that a considerable portion of the shore of Lake Michigan is formed by high, steep banks of clay, sand and gravel, and that these are being continually undermined, thrown down and borne away by the restless activity of the waves. The rate at which the land is thus being swept into the lake becomes a question of importance, but it should be understood that the lake is not advancing at all points, and that the rate of its advance at different points is not uniform. The encroachment seems to be most rapid in the neighborhood of Racine, and by measurements it was ascertained that in the forty years that elapsed between the surveys of 1835 and 1875 the abrasion of the shore in Milwaukee county ranged at different points from two to five and one-half feet. The material washed out from the shore is borne southward and accumulates rapidly on the north side of all the solid piers that extend out from the shore.

The soil of Milwaukee county, generally speaking, is abundantly rich and adapted to the growth of the usual crops in this climate and latitude. The greater portion of the county was originally covered with a heavy growth of timber, among which were the following species or kinds: Hard and soft maple, white birch, hickory, white and red cedar, white and red beach, black and white walnut, white and yellow pine, tamarack, sycamore, hackberry, poplar, balm of Gilead, aspen, white, red, burr and pin oak, basswood and common and slippery elm. Several of these, as the red cedar, pine and sycamore, were very scarce, however, and were found but rarely, but the bass-wood, that true indicator of a moist and rich soil, was more plentiful, as were also the other trees mentioned. Where these dense forests existed a marked effect was noticed upon the climate in several particulars. They protected the houses and cattle from the rigors of the north winds of winter and from the fierceness of the burning sun in summer. They preserved the moisture of the ground, and of the air, and rendered permanent and uniform the flow of water in springs, brooks and rivers. By the fall of their leaves, branches and trunks they restored to the soil those elements of vegetable life and growth that would, without this natural process, become less rich and productive. The leaves of the trees absorb the carbonic acid from the atmosphere and restore it to the oxygen, thus rendering it more pure and better suited for respiration by man and animals.

As regards climate, Milwaukee county is about the same as that of other sections of the state in the same latitude, except that it has the benefit of proximity to Lake Michigan, the influence of which prevents the extremes of heat and cold from which the inhabitants of the inland localities sometimes suffer. The winters, usually long and severe, are occasionally mild and almost entirely without snow. The ground generally becomes frozen to a considerable depth, and the rivers and ponds are bridged over with ice. The snow usually falls in December and continues until March, but the "January thraw" often carries off the snow and occasionally dissolves the ice in the rivers. The Milwaukee river generally becomes closed with ice in the latter part of November and becomes open sometime in March. Lake Michigan has a very sensible effect upon the climate by equalizing the temperature making the summers less hot and the winters less cold than they would otherwise be. Hence the difference between the mean temperature of winter and summer is several degrees less at Milwaukee than at a point in the same latitude in the western part of the state About the same difference is observed when we compare the mean temperature of winter and spring at the same places; the change from winter to spring being more sudden in the interior than on the lakes. This fact is also inferred from the vegetation of spring, for it has been ascertained by direct observation that in Waukesha county the early spring flowers show themselves about ten days earlier than on the lake. In the spring vegetation, in places remote from the lake, shoots up in a very short time and flowers begin to show their petals, while on the lake shore the cool air retards them and brings them more gradually into existence. Another effect of the lake is, as perhaps might be expected, to create a greater degree of humidity in the atmosphere, and hence a greater quantity of, rain. It is worthy of remark, however, that fogs do not occur with any great frequency, and Milwaukee is comparatively free from that inconvenience. Fogs are often seen lying on the surface of the lake itself, and vessels often experience trouble in making their way through them, but the mists appear to be dissipated upon approaching land.

In speaking of the flora of Milwaukee county it should be noted that it belongs to the heavily timbered land district. In its primitive state it abounded in plants of an interesting and useful character, embracing all varieties, from the stately oak which towered its head above the other trees of the forest to the humblest "wild wood flower." The openings in the forests were covered with a profusion of flowers of every form and hue, which changed with every change of season. In the wet natural meadows was found the different kinds of the plant family known by the scientific name of Carices, and this grew in great abundance, being annually cut by the pioneer farmers for hay. It was a highly important aid in the settlement of the new country, for it enabled the early inhabitants to support their teams and stock until artificial meadows could be prepared. Many of these natural meadows were occasioned by the dams of the beaver. A list of the different plants native to the county, with their scientific botanical names, is, of course, not within the province of this work, but suffice to say that numerous prepared specimens have been distributed among botanists of note and by them properly arranged and classified. The specimens were found to embrace about 150 of the natural orders or families, 450 genera, and at least 1,000 species — all found within thirty miles of the city of Milwaukee. A soil so adapted to the growth of wild flowers and plants was found to yield readily to the demands of the agriculturist, and in the production of the staple products of the farm the agricultural districts of Milwaukee county rank with those of any other section of the state.

The natural fauna of this portion of Wisconsin, with the exception of some of the smaller animals, has, of course, largely disappeared with the destruction of the forests. Of the large game none are now to be found within the domain of Milwaukee county, but the black bear, badger, otter, common wolf, red fox, lynx and wildcat, together with deer in large numbers, are among the species mentioned by the earlier records. But there are probably no specimens of these animals now remaining in the county. These animals had a range of the entire forests of the county. The coulees and ravines running down to the streams were the natural haunts of wolves and wolverines, and these lingered upon the outskirts of settlements after many others of the wild denizens of the forest had disappeared. The native fauna of the county is not yet extinct, however, as the grey, fox, black, red and striped squirrels are still found in considerable numbers, and the muskrat and rabbit have their habitat in the localities suited to their abode.

But the demands of civilization and the gigantic strides of progress in Milwaukee county during the past seventy-five years have changed the old order of things for the new, and where were once the hunting grounds of the red man are now to be found the marts of trade of the pale-face. In the succeeding pages an attempt has been made to give the story of this metamorphosis somewhat in detail.