Green County, Wisconsin - Chapter 2: Topography and Geology, 1884

Chapter 2: Topography and Geology

Lead has been found so far east in Green county that we may consider the whole of it as lying in the "Lead Region." It will be profitable, in this chapter, to begin with

I. Topography

Unlike most regions which nature has selected for the reception of metallic ores and useful minerals, the Lead Region bears no evidences of any sudden disturbances,or violent action of physical laws. The effects produced by igneous and eruptive agencies are wanting, i^aults and dislocation of strata are nowhere found. The only irregularities are slight upheavals, or bending of the strata (and these never of great extent) producing changes of but a few feet from the normal dip.

Between the geological condition and the general surface contour of the country, there is no direct correlation. The existence of a hill or valley on the surface is not due to a subterranean elevation or depression of the surface, as is by many supposed; and whatever irregularities exist, must be chiefly attributed to the milder natural agencies now constantly at work, - such as running water, frost, winds, etc., acting through an immensely long period of time.

Drainage. - The most marked and persistent feature of the Lead Region is the long dividing ridge, or water-shed, which, commencing near Madison, in Dane county, continues almost directly west to the Blue Mounds, a distance of about twenty miles. Here it takes a slight bend to the southwest for fifteen miles until it reaches Dodgeville, where itresumesits westerly course until it terminates in the bluffs at the confluence of the Wisconsin and Mississippi rivers. Its total length is about eighty-five miles. Two points are noticeable: one is, its gentle uniform directness of outline (it being subject to but few and unimportant flexures); and the other is its parallelism with the Wisconsin river so long as the latter holds an approximately westerly course - the summit of the ridge being always about fifteen miles from the river.

The divide maintains an average elevation of about 600 feet above Lake Michigan and is seldom less than 500, or more than 700, except at the Blue Mounds, where it gradually rises east and west for several miles, until it attains an elevation at the west mound of 1,151 feet. This, however, is an extreme case, and in fact, the only marked exception to its general level. In the town of Mount Hope, Grant county, a slight decrease of elevation commences and continues to the western end of the divide, where the elevation is about 430 feet, at a point within a mile of both the Mississippi and Wisconsin rivers.

There are two main branches or sub-divisions .of the water-shed. Of these, the western is the ridge which separates the waters that flow into the Platte and Fever rivers from those which flow into the Pecatonica. It leaves the main divide in the town of Wingville, Grant county, and passing through the towns of Belmont and Shullsburg, in Iowa county, in a southeasterly direction, passes out of the State in the town of Monticello, in the same county. Tliis ridge is not so conspicuous as the main watershed either for the directness of its course or the uniformity of its elevation. The most e'en- spicuous points on it are the Platte Mounds, whicli appear from a distance very high, but are, in reality only relatively so - their actual elevation being only about 700 feet above Lake Michigan. The ridge appears to slope somewhat, in its approach to Illinois - its average elevation tliere being about 500 feet.

The easterly sub-division, and the one especially of interest to the people of Green county, is that which separates the waters of the Pecatonica and Sugar rivers. It may be said to begin at the Blue Mounds, or a couple of miles east of them, and pursuing quite a devious course through the town of Primrose, in Dane county, and of Washington and Monroe, in Green, it crosses the State line in the town of Jefferson. This ridge, which presents a conspicuous figure in the surface contour of Green county, is characterized by a much greater want of uniformity in its general course, and by its irregular elevation. It is much narrower than either the main ridge or the western spur, already described, more abrupt in its slopes, and contains quite a large number of hills and low places, especially in the towns of Primrose and Perry, in Dane county and in those of York and New Glarus in the county of Green, in which towns, the streams head within comparatively short distances of each other, on opposite sides of the water-shed.

/Streams. - The present situations of the streams in the Lead Region was probably never modified or influenced by drift or glacial agenies. It follows then that the location of streams not only in Green county but in the others of the Lead Region, must have depended on the natural configuration of the country, and the superior advantages of certain strata in certain positions, predisposing them to become the beds of streams. Other things being equal, surface waters would naturally form a channel first in the more soft and easily erosible strata lying along the line of strike of some soft formation and would cause a river to conform its channel to its out-cropping edge. Simultaneously, its tributaries would shape their channels, approximately at right-angles to the river, under the following conditions: When the general slope and drainage of the country is not contrary to the geological dip of the formations; which, in the Lead Region, does not appear ever to have been the case. The tributaries on one side of the river thus formed, would conform themselves to the natural dip of the underlying strata, sloping toward the main river, and would be found wherever there were depressions, or irregularities in the surface suitable to their formation. These would, at their inception, approximate to their final length and course, and future changes in them would be confined to the deeper erosion of their beds and widening of their valleys; the formation of lateral branches; the division of the head of the stream into several smaller sources; and, finally, the gradual recession of all the subordinate parts.

With the tributaries on the other side of the pi'incipal river, a different order would prevail, as regards their position and growth. They would at first be the merest rivulets and increase only from erosion; and their beds would lie across the edges of the strata. There would be only a very limited extent of country tributary to the river on this side - the great volume of its water being derived from the tributaries of the other side. The dividing ridge would thus be very near the river, and a second set of long streams, tributary to some other river, would here take their rise and flow away.

In the course of time, the main river would slowly cut its way through the soft formation in which it had its original bed, into and through those which underlaid it. This might at first be accompanied by a slight recession parallel to the line of strike; such a movement, however, could not be of long duration, but would become less as the valley became deeper; because any such recession would necessitate the removal of all the overlying formations. Finally, the small streams flowing across the strata would cut their valley back from the river; the dividing ridge would recede and their sources would, from the position of the strata, be in steep and precipitous ravines. Such in brief, appears to be the theory of the formation of streams in the Lead Region and of course in Green county, of which region the county forms a part.

Dimimition of Streams. - In comparing the streams in Green county and in other counties of the Lead Region, at present, with those recorded in the government surveys, it will be found that many of the smaller ones are entirely dry and others nearly so. Numerous springs which formerly furnished an abundant supply of water, are now dry and have been replaced by wells, sunk to obtain water from a deeper stratum.

The larger streams of the Lead Region contain a much smaller amount of water than heretofore. Some places can be found where mills, formerly operated by water-power, have been abandoned on account of a diminished supply, or absolute failure, of water.

This diminution is not confined to surface water, springs, streams, and the like, but it is true, to a greater or less extent, of all the mining ground of the Lead Region. In many instances, this circumstance alone has led to the re-opening and profitable working of mines which years before had been abandoned on account of too much water - with ore "going down" in the crevices.

It is probable that cultivation of the land is the chief cause of this decrease, as a much greater amount of surface is thus exposed, and eraporation takes place more rapidly and in larger quantities. Removal of the timber is, without doubt, another cause of this decrease. The soil of the timbered land contains more moisture than that of the prairie; and, in all countries, the removal of the timber has always been followed by a marked decrease of the water supply. This was notably the casein the Harts mountains of Prussia after the fir and hemlock were removed. When the mountain sides were again covered by indigeous trees that had been planted by order of the government, their growth was found to be attended by an increase of water in the streams and springs.*

Springs and Wells. - The Lead Region (and Green county as a portion of it) is one of the best watered tracts in the State. Springs are very numerous, both about the sources of the streams and frequently in their banks. They are found in all the geological formations.

In such portions of the country as are not liberally supplied by nature with springs, water is easily and abundantly obtained by means of wells. Their average depth is about twentyfive feet; this, however, depends chiefly on the locality in which they are sunk - those on the ridges and prairies being deeper than the rest. Wells are sometimes obtained by drilling, such borings being chiefly confined to the prairies. They are then furnished with a wind-mill pump and supply an abundance of clear water for stock and farm purposes.

Nearly all the water in the Lead Region, whether in springs or wells, holds in solution a small portion of lime and magnesia, and a still smaller quantity of sodium, iron^ alumina and silica. The presence of these salts usually gives the water what is called a hard taste, which is more noticeable in the limestone than in the sandstone springs, and not infrequently induces people to believe them possessed of medical properties.

The following analysis, which is believed to be an average sample of the quality of the water in Green and the other counties of the Lead Region, is inserted to show thesmall amount of foreign substances found. The water analyzed was taken from a well a short distance northwest of the incorporated village of Brodhead. One gallon, United States standard measure, of this water, was found to contain of solid salts, 13.2720 grains, as follows:

Prairie and Forest. - The prairie^area of the Lead Region is comparatively small and seems to be chiefly a continuation of the great prairies of Illinois. The most extensive prairie is that found in the southern part of Grant and La Fayette counties, comprising the towns of Jamestown and Hazel Green in the first mentioned county, and of Benton, New Diggings, Shullsburg, Seymour, Monticello and Gratiot, in the last. From this prairie, there is a branch extending in a northwestern direction (corresponding to the eastern sub-division of the water-shed previously alluded to), until it unites with the main water-shed; here it branches east and west. The western extension forms a prairie in the towns of Glen Haven, Patch Grove, Little Grant and some parts of Fennimore and Wingville, in the county of Grant. The eastern prairie follows the main divide already described, the prairie being from six to ten miles in width. Between the east and west branches of the Pecatonica, there is a prairie, including most of the towns of Waldick, in Iowa county, and of Fayette and Wiota in La Fayette county. In Green county, the principal prairie is found in the towns of Monroe, Clarno, Sylvester and Washington.

We have thus given, in brief, a description of the prairie land of the Lead Region, including Green county. There exist small, isolated patches of timber, in this area, as well as stnall prairies or openings in the remainder of the country under consideration - not included in the prairie area and which is mostly timbered land. The original area of prairie appears, from the government surveys, to have been somewhat greater than what would be assigned to it at present.

Now (1884), the original forests of large timber have been mostly cut down, except about the Wisconsin river bluffs, such timber as is now found being a second growth of black oak, white oak, burr oak, maple, hickory, poplar and elm, the trees being of small size, seldom more than a foot in diameter.

Before entering upon a consideration of the geological formations of the Lead Region it is thought proper to call the attention of the reader to its surface geology.

Soil and Subsoil. - The quality of the soil of the lead region (and, of course, of Green county, of which it is a part) is chiefly dependent on the character of the subjacent formations. The subsoil appears to be derived directly from the decay and disintegration of the strata, of which it is the residuum. South of the principal water-shed the subsoil is clay, almost without exception, having a thickness of from three to six feet, depending on the configuration of the underlying rock formation. This is the average thickness on comparatively level ground; on side hills it is usually much thinner, the greater part having been washed down into the valleys below.

The amount of lime, magnesia and alkaline earths in the subsoil and soil, together with the vegetable mole in the latter, constitutes a soil which, in its virgin state, is unsurpassed for richness and fertility. The number of successive wheat crops which, in years past, were raised without regard to rotation, on some of the prairie farms, attest its native strength; as also tlie marked decline in fertility of the soil when this has been done shows the inevitable retribution which follows the practice. The exceptions to the clay soil in Green county will be hereafter mentioned; so also as to the transportation of the component materials of the soils.

approach to peat yet known in the lead region. One of these is situated on Jordan creek, on the easthalf of sections 21 and 28, in township 2 north, of range 6 east (town of Jordan), and comprises from 150 to 200 acres. The other locality is on the Little Sugar river, near the center of section 11, in township 8 north, of range 7 east (town of Washington). As the conditions under which they exist are similar, one description will answer for both.

The turf is underlaid by an impervious stratum of blue clay, which holds the water and nourishes a vegetable growth about four feet thick, which, in this vicinity, is known as peat. When cut and dried it burns similarly to peat, but with so large a residuum of clay, sand and ashes as to render it unfit for economic purposes. Brick Clay. - Clay suitable for making brick is found in many parts of Green and adjoining counties; but, in the city of Monroe, there is found a clay having a peculiarity not noticeable elsewhere; two kinds of brick are made from the same kind of clay. One is a red brick similar to all common red brick; the other is a cream colored brick of very handsome appearance, closely resembling the Milwaukee brick. The difference in color is due to the difference in burning - the red color being caused by a greater and long continued heat. The origin of the clay of which the brick is made is a matter of some doubt. It does not have exactly the appearance of a drift clay; and, if not, its situation indicates that it must have undergone some subsequent re-arrangement.

Glacial Drift. - The lead region is a driftless tract of country; not a single bowlder, pebble or clay of foreign origin being found within its limits, except in three or four isolated cases. The northern boundary line of the driftless region lies far to the north of the lead region. The eastern line is in Green county; it commences on the west side of the Pecatonica river, crossing the State line at the southwest corner of the town of Cadiz, which is also the southwest corner of the county. From this point it proceeds almost in a straight line to the city of Monroe. Thence north, it runs along the dividing ridge between the Pecatonica and Sugar rivers, until about two miles south of New Glarus, where it takes a northeasterly course and passes out of the county about a mile west of Belleville, in Dane county. The course thus indicated is its present line, as shown by erratic bowlders lying upon the surface. If the drift deposits originally extended farther westward, no trace thereof now remains. East of the line described, bowlders are found in all parts of the county with more or less frequency. The boundary line, where bowlders are now found, does not appear to conform at all to the surface features, but crosses the valleys of the streams and the ridges between them with equal impartiality.

The different kinds of rock found in the drift are so numerous that it would require quite a catalogue to enumerate them all. It will be sufficient to state that the great bulk of them are granite, metamorphic or trappean - the most frequent being the varieties of granite and gneiss, and next to them the trappean rocks. Chloritic rocks and those of a schistoze structure are also quite numerous. In addition to these, there are, in certain places, beds of gravel, sand and clay.

The distribution of the bowlders does not appear to be very regular in Green county; in fact the whole of the county verges 'so near the western boundary of the drift, that comparatively small deposits were made here ; which are quite insufficient to exemplify any general laws of distribution. No difference is observable in their frequency between the eastern line of the county and the western line of the drift. The bowlders are of various sizes from a few inches to two or three feet in diameter and are always rounded and worn smooth. They are frequently found quite numerous in one place, and then scattered along at very distant intervals, on the same kind of ground, but

Gravel beds are not very frequent, although they are found in several places in the county. There is one situated very near the boundary of the drift, on the northwest quarter of section 4, in township 1 north, of range 7 east (town of Clarno), where there is a bed ot gravel about eight feet thick, underlaid by a bed of stratified sand and clay about four feet thick. This sand is very tine, and has just enough clay mixed with it to make a good article of moulding sand for iron foundries; it would give a fine impression and make a smooth <;asting. A similar bed is seen about two miles east of the preceding, on the southwest quarter of section 2, in township 1 north, of range 7 east, (town of Clarno), where the drift sand and gravel have accumulated to a thickness of about twelve feet. Another bed, like the other two, is in existence on the northwest quarter of section 2, in township 1 north, of range 7 east, (town of Clarno). There are several other beds in various portions of the county.

The amount of drift clay in this county is comparatively small, it probably having been dissolved out and washed away from the greater portion of the surface. It is to be found however; and particularly on the northwest quarter of section 25, in township 3 north, of range 7 east, (town of Washington), where a well has been sunk in the drift. There is here a thickness of about twenty feet of slate-colored clay, full of small pebbles.

The geological formations underlying Green county are : (I.) the Potsdam sandstone ; (II.) the Lower Magnesian limestone; (III.) St. Peters sandstone; (IV.) Trenton (Buff and Blue) limestone; and (V.) Galena limestone. It is proposed, in this connection, before describing the geographical boundaries, lithological characteristics and paleontology of these formations in Green county, to give a brief history of their origin:

I. - Potsdam Sandstone. After the great Archaean upheaval, there followed a long period, concerning which very little is known - a lost interval in geological history. It is only certain that immense erosion of the Archaean strata took place, and that in time the sea advanced upon the island, eroding its strata and redepositing the wash and wear beneath its surface. The more resisting beds withstood this advance, and formed reefs and rocky islands off the ancient shore, about whose bases the sands and sediments accumulated, as they did over the bottom of the surrounding ocean. The breakers dashing against the rocky cliffs, brought down masses of rock, which imbedded themselves in the sands, or were rolled and rounded on the beach, and at length were buried, in either case, to tell their own history, when they should be again disclosed by the ceaseless gnawings of the very elements that had buried them. In addition to the accumulations of wash and wear that have previously been the main agents of rock formations, abundant life now swarms in the ocean, and the sands become the great cemetery of its dead. Though the contribution of each little being was small, the myriad millions the waters brought forth, yielded by their remains, a large contribution to the accumulating sediments. Among plants there were sea-weeds, and among animals, protozoans, radiates, mollusks and articulates, all the subkingdoms except the vertebrates. Among these the most remarkable, both in nature and number, were the trilobites, who have left their casts in countless multitudes in certain localities. The result of the action of these several agencies was the formation of extensive beds of sandstone, with interstratified layers of limestone and shale. These surrounded the Arch;ean nucleus on all sides, and reposed on its flanks. On the Lake Superior margin the sea acted on the copper and iron-bearing series, which are highly ferruginous, and the result was the red Lake Superior sandstone. On the opposite side of the island, the wave action was mainly upon quartzites, porphyries and granites and resulted in light-colored sandstones. The former is confined to the immediate vicinity of Lake Superior ; the latter occupies a broad, irregular belt bordering on the Archaean area on the south, and, being widest in the central part of the State, is often likened to a rude crescent. It will be understood from the foregoing description, that the strata of this formation lies in a nearly horizontal position, and repose unconformably upon the worn surface of the crystalline rocks. The close of this period was not marked by any great upheaval ; there was no crumbling or metamorphisra of the strata, and they have remained to the present day very much the same as they were originally deposited, save a slight arching upward in the central portion of the State. The beds have been somewhat compacted by the pressure of superincumbent strata and solidified by the cementing action of calcareous and ferruginous waters, and by their own coherence, but the original character of the formation, as a great sand-bed, has not been obliterated. It still bears the ripple-marks, cross-lamination, worm-burrows, and similar markings that characterize a sandy beach. Its thickness is very irregular owing to the unevenness of its Archaean bottom, and may be said to range from 1,000 feet downward. The strata slope gently away from the Archaean core of the State and underlie all the latter formations, and may be reached at any point in southern Wisconsin by penetrating to a sufficient depth, which can be calculated with an approximate correctness. As it is a waterbearing formation, and the source of fine artesian wells, this is a fact of much importance. The interbedded layers of limestone and shale, by supplying impervious strata, very much enhance its value as a source of fountains. II. - lower Miigiit'!<i((n Limestone, During the previous period, the accumulation of sandstone gave place for a time to the formation of limestone, and afterward the deposit of sandstone was resumed. At its close, without any very remarked disturbance of existing conditions, the formation of limestone was resumed, and progressed with little interruption till a thickness ranging from fifty to 250 feet was attained. This variation is due mainly to irregularities of the upper surface of the formation, which is undulating, and in some localities may appropriately be termed billowy, the surface rising and falling 100 feet in some cases, within a short distance. This, and the preceding similar deposit, have been spoken of as limestone simply, but they are really Dolomites, or Magnesian limestones, since they contain a large proportion of carbonate of magnesia. This rock also contains a notable quantity of silicia, which occurs disseminated through the mass of rock; or, variously, as nodules or masses of chert; as crystals of quartz, filling or lining drusy cavities, forming beautiful miniature grottoes ; as the nucleus of oolitic concretions, or as sand. Some argillaceous matter also enters into its composition, and small quantities of the ores of iron, lead and copper, are sometimes found, but they give little promise of value. The evidences of life are very scanty. Some sea-weeds, a few mollusks, and an occasional indication of other forms of life, embrace the known list, except at a few favored localities where a somewhat ampler fauna is found. But it is not, therefore, safe to assume the absence of life in the depositing seas, for it is certain that most limestone has originated from the remains of animals and plants that secrete calcareous material, and it is most consistent to believe that such was the case in the present instance, and that the distinct traces of life were mostly obliterated. This formation occupies an irregular belt skirting the Potsdam area. It was, doubtless, originally a somewhat uniform band swinging around the nucleus of the state already formed, but it has since been eroded bj^ streams to its present jagged outline.

III. - St. Peter's Sandstone. At the close of this sandstone-making period there appears to have been an interval of which we have no record, and the next chapter of the history introduces us to another era of sand accumulation. The work began by the leveling up of the inequalities of the surface of the Lower Magnesian limestone, and it ceased before that was entirely accomplished in all parts of the State, for a few prominences were left projecting through the sand deposits. The material laid down consisted of a silicious sand, of uniform, well-rounded - doubtless well-rolled - grains. This was evidently deposited horizontally upon the uneven limestone surface, and so rests in a sense unconformably upon it. Where the sandstone abuts against the sides of the limestone prominences, it is mingled with material derived by wave action from them, which tells the story of its formation. But aside from these and other exceptional impurities, the formation is a very pure sandstone, and is used for glass manufacture. At most points the sandstone has never become firmly cemented and readily crumbles, so that it is used for mortar the simple handling with pick and shovel being sufficient to reduce it to a sand. Owing to the unevenness of its bottom, it varies greatly in thickness, the greatest yet observed being 212 feet, but the average is less than 100 feet. Until recently, no organic remains had ever been found in it, and the traces now collected are very meagre indeed, but they are sufficient to show the existence of marine life, and demonstrate that it is an oceanic deposit. The rarity of fossils is to be attributed to the porous nature of the rock, which is unfavorable to their preservation. This porosity, however, subserves a very useful purpose, as it renders this pre-eminently a water-bearing horizon, and supplies some of the finest artesian fountains in the State, and is competent to furnish many more. It occupies but a narrow area at the surface, fringing that of the Lower Magnesian limestone on the south.

IV. - Trenton Limestone. A slight change in the oceanic conditions caused a return to limestone formation, accompanied with the deposit of considerable clayey materia], which formed shale. The origin of the limestone is made evident by a close examination of it, which shows it to be full of fragments of shells, corals, and other organic remains, or the impressions tiiey have left. Countless numbers of the lower forms of life flourished in the seas, and left their remains to be comminuted and consolidated into limestone. A part of the time the accumulation of clayey matter pi'edominated, and so layers of shale alternate with the limestone beds, and shaly leaves and partings occur in the limestone layers. Unlike the calcareous strata above and below, a portion of these are true limestone with less quantities of other metals. The formation abounds in fossils, many of them well preserved, and, from their great antiquity, they possess uncommon interest. All the animal sub-kingdoms, except vertebrates, are represented. The surface area of this rock borders the St. Peter's sandstone, but, to avoid too great complexity on the map, it is not distinguished from the next formation to which it is closely allied. Its thickness reaches 120 feet.

It it here appropriate to consider the geographical boundaries, lithological characteristics, and paleontology of the several formations in Green county, in the same order as has been followed in giving the history of their origin.

Potsdam Sandstone.* - This formation is not exposed anywhere in Green county; but south of the Wisconsin river, it is found as the bed rock of Otter, Mill and Blue Mounds creeks and their various tributaries, as far south as township 7, of the various ranges. Here it disappears owing to the southerly dip of the formation, and the sudden rise of the country to

of the Potsdam sandstone being- an underlying: formation of Green county, thong-h not exposed anywhere, so far as Is known, within its limits, it is thought best to give its geographical boundaries, etc., in the Lead Region.

the south. This explains why it nowhere appears in Green county. The valley of the Wisconsin river lies in this sandstone, forming a very level plain,from two to three miles wide and extending from Sauk City to a point about four miles above the mouth of the river. Good natural exposures are seen in the bluffs on each side of the river, in which the various strata may be traced uninterruptedly for miles.

The sandstone beds of the Potsdam are usually composed of a very soft and friable sand, frequently crumbling readily between the fingers, especially if it is white. The upper beds are more frequently white than the others, although white beds are not uncommon in all parts of the formation. In general, the lower beds are yellow or brownish in color. The great inequality in the hardness of the several strata of the Potsdam is frequently the cause of the formation of terraces by erosion, which are often a conspicuous feature of the valleys in the vicinity of the Wisconsin river.

South of the Wisconsin river, about the headwaters of Blue Mounds creek and Mill creek, the upper bed of the Potsdam consists of a red and very ferruginous sandstone, often containing seams of iron ore andiron conci'etions. The coloring matter appears to be partially soluble, and, becoming washed out by the rain, colors the soil in some places to a considerable extent.

The fossil remains of this formation seem to be chiefly confined to the calcareous strata and argillaceous shales. These remains consist chiefly of Lijigula Aurora and Dicellocephelus Mianesotensis, - the former being quite small and usually having the shell remaining; sometimes, however, the shells have been ground up so that only a few fragments are found, disseminated through the shales. The trilobites are seldom or never found entire, but usually the cephalic portion, the pygidium, or still smaller fragments. The various sandstone beds of the Potsdam are usually unfossiliferous. The upper bed of sandstone seldom contains anything but Scoltthus, which, in some localities, is very numerous.

Lower Magnesian Limestone. - South of the Wisconsin river and north of the main watershed, the Lower Magnesian limestone occupies a tract of land lying about the heads of all the smaller tributary streams, although seldom found so far back as their springs. Passing down any of the streams, we gradually pass below its surface, and its outcrops are seen gradually higher in the hills, until, on reaching the Wisconsin river, it forms the cap of all the bluffs from Sauk City to Boscobel, usually appearing in bold and rugged cliffs, lending a very picturesque effect to the scenery of the river. It forms also the valley of the Mississippi as far south as Glen Haven where it passes under the surface. Passing south of the divide which separates the waters which flow into the Wisconsin from the Pecatonica, it is found in the branches of the latter stream as far north as the north line of township 5, in ranges 5 and 6 east. Proceeding westward, it is not again encountered until the Platte and Grant rivers are reached, where it is found as the bed-rock of those streams; and, in township 5 north, of range 3 west, it covers a large portion of the township.

In Green county, there is but one exposure of the formation. It is in the valley of the Sugar river, about three miles above Brodhead. It commences a short distance north of the center of section 15, in township 2 north, of range 9 east, (town of Decatur), where it has a width of about half a mile. In passing into township 3, in the same range (town of Albany) it widens to nearly two miles. It then becomes narrower; attains its greatest elevation above the river at the village of Albany; and finally disappears beneath the surface of the river about a mile and a half above that place.

After passing through the transition beds separating it from the Potsdam sandstone, the Lower Magnesian assumes all the qualities characterizing dolomite. It is very hard, compact, and close-grained, of a grayish-white color.

Beds of flint or chert are contained in all the strata, irrespective of geological position, differing, however, considerably from the flint found in the Galena limestone, in that they are more regularly segregated, forming layers by themselves, and are not so promiscuously distributed through the formation.

The flint of the Lower Magnesian limestone is much whiter and more liable to decomposition than that of the Galena. There are also geodes and cavities lined with drusy quartz-crystals, which have never been seen in the Galena limestone, but are very abundant in the Lower Magnesian. The crystals are of many colors - white, yellow and rose color predominating and often affording beautiful cabinet specimens.

The Lower Magnesian is a formation of extremely variable thickness; the greatest known in the lead region is about 250 feet; this, however, is seldom seen. This formation is characterized by the extreme rarity of its organic remains. The few fossils seen have been found imbedded in the drusy quartz with which the formation abounds and usually in the form of casts. Some, however, have been found in the limestone.

St. Pete7'^s Sandstone. - The formation known as the St. Peter's sandstone is found in the valleys of the Grant, Platte and Pecatonica rivers and their tributaries. In Green county, it forms the valley of the Sugar river and its branches, this valley being, in many places, as wide as that of the Mississippi. North of the dividing ridge it is found about the headwaters of the streams which flow into the Wisconsin, having its northern outcrop usually within two or three miles of the river and as far east as Boscobel forming a portion of the bluffs which inclose the river valley.

'J'he St. Peters sandstone differs from the Potsdam sandstone in that it contains no beds of limestone or shales interstratified with it, but presents at any given locality a homogeneous structure through its entire thickness. Its colof varies from snow white, through all the shades of yellow, to a very dark red, and in texture, from friable crumbling sand, to compact and fine-grained stone. Beneath the microscope, the particles of sand appear rounded and and water-worn. The same color and texture usually exist through the entire thickness at any given place.

The St. Peters formation frequently impresses upon the surface of the country an appearance of terraces, although no traces of terraces, such as are formed in river valleys by changes of level, have anywhere been observed. This is most readily seen in those districts where it becomes the surface rock over any extended portion of country.

The exposures of St. Peter's are very frequent in Green county, where, in addition to the continuous exposures, small hills are frequently seen with flat tops, v^hich have been denuded nearly down to the formation under consideration.

The varying hardness of the upper bed of the St. Peters, some portions, especially the white, being quite soft and friable, and others nearly as hard as quartzite, due, perhaps, to its greater or less impregnation with iron, appear to have caused an unequal resistance to disintegration, which has resulted in the formation of knobs, as they arc called. These are isolated pillars of sandstone, which shoot up in picturesque castellated forms, frequently exposing the entire thickness of the formation and forming very conspicuous objects in the landscape.

The peculiarity of the hardness of the upper beds of the St. Peters proves of great assistance in tracing the outlines of the formation, in determining its thickness and in detecting irregularities in the surface contour. This formation differs very much in its thickness in different localities, although this does not appear to be the case so much in the Lead Region as near the northern outcrop of the formation, where it is in some places as thin as forty feet, and in others, not more than a mile or two distant, it is 100 or even 150 fef^t thick, depending, seem- ingly, on the varying thickness of the underlying Lower Magiiesian limestone. The layers consist of subordinate parts of very various lamination, dipping in various directions.

There are several points in the lead region, where slight upheavals of the foi'mation appear to have taken place. The sandstone on the small branch on sections 35 and 36, in township 2 north, of range 6 east, (town of Jordan, Green county), slopes gently toward Skinner creek, which appears to lie in a slight depression or synclinal valley. Passing over the ridge between Skinner and Jordan creeks, a slight anticlinal ridge is seen by means of observations on the top of the St. Peters, which is exposed in numerous small dry runs. The top of the formation is found to be thirty feet higher on the ridge than at either of the creeks. Although disturbances of this kind are extremely rare and infrequent, yet in this case, as in a few others, the variations from the normal dip are too plain to be mistaken.

The St. Peters sandstone seems everywhere to be perfectly destitute of orgaiiic remains. The only indication of metal seen in this formation is the presence of small conci-etions oi sandstone, cemented by a ferruginous substancf . This is due to the decomposition of iron pyrites or marcasite, as is proved by its existence in various stages of decay. These concretions are not confined to any. particular part of the formation, but are much more abundant in the upper beds. They are frequently perfectly spherical, and, when they occur in the dark colored sandstone, are often surrounded by a white ring about half an inch in width, from which the coloring matter seems to have been absorbed. They have been noticed with more or less frequency in various places. They can be seen in abundance in the road near the center of section 3, in township 1 north, of range 6 east (town of Cadiz, Green county). The lower bed is full of irregular cavities and small round holes about one-fourth of an inch in diameter. The upper bed of the sandstone is colored green by some salt of iron, and in it is a seam of green and ferruginous matter.

It is a peculiarity of this formation that the stone hardens on exposure to the weather. In examining any natural exposure, it is found to consist of an outer indurated'shell and an inner and softer sandstone. This is a valuable quality, causing it to be easily quarried and dressed, and enabling it afterward to withstand the influences of the weather. In addition to this, it is easy to find almost any color that may be desired. -

Trenton {JBnff and Blue) Limestones. - It will not be necessary to enter into a detailed description of the ground covered by this formation. It is sufficient to say that it is always found between the lowest bed of the Galena limestone (hereafter to be described) and the top of the St. Peters sandstone, and having an average thickness of about fifty feet.

The Blue limestone is remarkable as being the purest in the Lead Region, and the nearest approach to the Trenton limestone of the eastern States, both in its lithological and paleontological characteristics. A very noticeable feature is its marked division into two parts; one very heavy-bedded, in layers of two or three feet thick, known as the glass rock, which constitutes the lower half; and the other, thin' bedded, in layers of two or three inches, graduating sometimes without much change into thinbedded Galena limestone above. It is at this point that the stratum of carbonaceous shale occurs, which is the line of demarkation between the Blue and Galena limestones, and as such, is an unfailing guide. It varies very much in its thickness, being from a quarter of an inch to a foot ormoi'e, but wherever a good exposure of the two formations is seen, it has uniformly been found.

East of range 8 east (that is, east of a north and south line drawn twelve miles west of the east boundary lines of the counties of Iowa and Lafayette) the presence of the Blue limestone is nowhere so clearly marked as west of this line. It is usually recognized by the outcropping of a quantity of highly fossiliferous fragments scattered through the soil, having a worn and bleached appearance. East of range 3, the fossiliferous Blue limestone has not been found; hence, none has been discovered in Green county which lies still^farther eastward. It is replaced by a yellowish limestone, containing but very few fossils and in all respects similar to the Buff limestone. The thickness between the Galena limestone and St. Peters sandstone remains as usual about fifty feet.

There are two exceptions to the foregoing general statement. A short distance south of the center of section 18, in township 1 north, of range 6 east (town of Cadiz, Green county), the Blue limestone re-appears in its full thickness, with all its characteristic fossils, but only covering a small area of ground. The second exception is situated on the southeast quarter of section 11, in township 3 north, of range 7 east (town of Mt. Pleasant, in Green county). It is known as the Marble Quarry, so named on account of the fine polish which may be given to the stone. The Blue limestone has here the same thickness, both of the thin and thick beds, as in the western part of the Lead Region. All the characteristic fossils are present, and in short, it presents all the usual lithological appearances. It appears to have been deposited in a basin-shaped depression, as the top of St. Peters is found to be much lower here than any where in the vicinity. Although separated many miles from other outcrop of the Blue limestone, it is evident that it was deposited under the same conditions, as in other localities. It makes a good article of burning-lime. * It takes a high polish, equal to marble, although large pieces can not be obtained.

Tlie Blue and Buff limestone are the lowest formations in which any ores are found in sufficient quantities to repay mining in the Lead Region. Large bodies of lead ore have from time to time been taken from this formation, but it seems to be more especially productive of zinCjboth as carbonate and sulplmret. Organic remains are found in the greatest profusion and in a very fine state of preservation, the rock in many places being entirely composed of them. In the Buff limestone, they usually occur as casts.

Galena Limestone. - The Galena limestone is by far the most important in respect to its metallic wealth of all the formations before considered. In it are contained all the mines of the southern and western parts of the Lead Region; and whenever mining has been carried on in the underlying Trenton limestones, lead is usually present in the overlying Galena. This limestone is the prevailing surface rock in the Lead Region. Its northern outcrop conforms closely to the main water-shed, being parallel to, and always within a few miles north of it. Its surface area is given as follows for each range in the Lead Region:

The Galena limestone is almost invariably a very compact, hard, crystalline rock, of a yellowish gray color, with numerous small cavities, sometimes filled with a softer material and sometimes lined with small crystals of calcite. The upper portion is usually thick-bedded and free from fiints, the layers being from one to four feet thick, while the lower portion almost invariably consists of several feet of layers from one to two inches thick. Good exposures of parts of this formation are frequently to be met with; it may be seen in cliffs and ledges on nearly all the streams in the Lead Region. It always weathers irregularly in these natural ex-

The formation is characterized by layers of flints, which, however, are not constant in their occurrence in the same beds at different localities. In some places, there are several beds of flints, which seem to be connected with the openings, and serve as a guide to them, while in others they are either entirely absent or occupying very different geological positions. The flints are sometimes found in separate layers, deposited conformably in the rock and often in irregular pieces distributed through the strata. They seem to be confined principally to the middle and lower parts of the formation although not entirely absent from any part.

The Galena limestone is, in many places successfully quarried as a building stone. This is chiefly the case in the southern and western parts of the region where the Bluff limestone or St. Peters sandstone cannot be obtained. The chief objection to it is the frequency of cavitie:- and soft places in it which render it difficult t( dress, and cause it to weather irregularly. Foi foundations, or any work where beauty of finish is not the chief object, it is a good and durabkstone. The organic remains of the Galena limestone are quite abundant, but do not exist in such profusion as in the l>lue limestone.

We have before remarked that the clay soils and sub-soils of the Lead Region appear to consist chiefly of those portions of the overlying Galena limestone and earthy Cincinnati shales which being insoluble in water were not removed by the gradual process of denudation.

Exceptions to the clay soil, usually found in the country covered by the Galena limestone, are found in the eastern part of La Fayette, and frequently in Green county, where the soil is quite sandy, owing to the disintegration of calcareous sand layers frequently found there in that formation. A few localities are cited below where the saT;^d is so abundant that the formation might be considered a sandstone wei*e it not for the occasional outcrops of Galena limestone in place. In the western part of the town of Jordan, Green county, (township 2 north, of range 6 east), on sections 2, 11 and 14, the ridges have a great deal of sand contained in the soil. The roads are frequently sandy, similar to those in a sandstone formation. Lying entirely without the drift, this circumstance led to a search for and discovery of the original beds.

At the village of Martin, on the southeast quarter of section 82, in township 1 north, of range 6 east (town of Cadiz, Green county), on the Pecatonica river, at the saw-mill, is a large stone quarry, of which the upper portion consists of Galena limestone in thin beds, containing considerable calcareous sand between the layers. The sand here is found in place.

On the ridge near the quarter-post on sections 29 and 32, in township 2 north, of range 6 east (town of Jordan), a great deal of sand is to be seen at an elevation of 150 feet above the top of the St. Peters; numerous concretions of iron are also to be found, similar to those usually found in the upper bed of that formation. East of the center of section 34, in township 3 north, of range 6 east (town of Adams), is another sandy ridge.

The agencies of the glacial period do not appear to have had anything to do with transporting the component materials of the soil; and, although a slight transportation has taken place, it is always merely local. For instance, in the valleys of the creeks which lie in the St. Peters sandstone, the soil is usually a rich clay loam, richer, in fact, than that of the adjacent ridges, because the best parts of the upland soils have been washed down and distributed over the surface of the valley.

"These [near Monroe] are the most easterly diggings in the lead region, and are chiefly interesting for that reason. They are situated about three miles and a half north of the city of Monroe. At present only two parties are at work:

" 7\ n. Whiie db W?dte. - Situated on the northeast quarter of section 14, in township 2 north, of range 7 east [town of Monroe]. The ore is found here in a flat sheet, accompanied by pipe clay, about twenty-three feet below the surface. The general course of the sheet is northwest and southeast, and produces only lead ore. The ground is quite free from water. The present parties have been working here six years, during which period they have produced 90,000 pounds of lead ore.

^^Frmne c5 Company. - Situated on the southeast quarter of section 10, in township 2 north, of range "7 east [town of Monroe], on the land of Henry Wilber. This is an east and west range, about half a mile northeast of the preceding. It was discovered in 1844, and has been proved for a distance of 700 feet. The lead ore is found in both vertical crevices and flat openings. There appear to be three principal vertical crevices, connected in places by horizontal sheets. They were worked by John Monahan from 1870 to February, 1872, chiefly in the winter season, during which time he produced 50,000 pounds. Mr. Frame took the ground in 1874, and produced 4,000 pounds in the first six months. The production since then could not be ascertained. The ground is quite dry, and the workings are about fifty feet below the surface. It is not probable that any extensive deposits exist in this vicinity. The ground appears rather to be such as, by careful working, will afford moderate wages to a few persons."*