w7ce /^ ''i>"^ 4&,iSii:a^^ Vol. 111. No. 3. January , 1907 MILWAUKEE NORMAL SCHOOL BULLETIN Physiographic Modeli of Wi isconsm Published Quarterly by the State Normal School, Milwaukee, Wis. F.nteied Jane IS, 1905, at Milwaukee, Wisconsin, at second class matter under Act of Congress, July 16, 1894. This book is DUE on the last date stamped below GB 126 vr7C2 Case.- De script ion of Southern Branch of the University of California Los Angeles Form L-1 A DESCRIPTION OF MODELS ILLUSTRATING THE Physical Geography of Wisconsin 1 I ,M '^-'-■^i '■ 0:' CALiFOBNIA, BY E. C. CASE MILWAUKEE A7 ^ c MODELS SHOWING THE PHYSICAL GEOGRAPHY OF THE STATE OF WISCONSIN. These models were constructed in the laboratory of the Depart- ment of Physical Geography and Geology of the State Normal School at Milwaukee. They are based on the last geological map of the state, published in Buckley's "Building Stones of Wisconsin," and have the same horizontal scale — 20 miles to the inch. The vertical scale is exaggerated 100 times, which seems an enormous amount, but is necessary to bring out the features of the eastern part of the state. As only a small portion of the state has been mapped by the topographic survey, a great many of the elevations have been taken from railroad profiles, data given by the first Geological Survey of the state, and by the U. S. Geological Survey. In the preparation of such a small scale model it was impossible to show all parts of the state with any great degree of detail; the attempt has been rather to show the features in a broad way, making rather a "sketch model" than one with pretensions to absolute accuracy. The characteristic features of • ^ different parts of the state have been indicated, as, for instance, the ^ residual mounds of the southwestern portion, the Baraboo Ridge, and the elongated ridges and lowlands on the eastern side of the state. The only previous attempt to make a model of the state was by Prof. King, who built a model somewhat larger than the present one, with a smaller vertical scale and on which he attempted to indicate the prominent features. These models are now rather difficult to obtain and are too large for ordinary class room work. All of the present models have been prepared on the same base, but have been colored differently to illustrate different features of the state's Physical Geography. The first shows only the Relief; the second shows the state as an Ancient Coastal Plain; the third shows the Glacial Deposits and the Driftless Area. The following descriptions of the models are taken largely from Prof. Case's new book, "Wisconsin — Its Geology and Physical Geog- raphy," just issued. >^^ THE SIMPLE RELIEF MODEL. The state is divided between two slopes; a long and gentle one to the south and a short and more precipitous one to the north. The water parting between these two slopes is very indefinite, for the natural slope of the land is obscured by the overlying drift of the Glacial period, and the highest area of the state, the source of most of the rivers, is fiat and swampy, so that the tributaries of the Mis- sis-sippi and of the St. Lawrence often head in the same swamp. No line can be drawn between the headwaters of the Montreal river and of the Flambeau, a tributary of the Chippewa. Fig. 1. Photograph of the Relief Model Cut Furnished by the Central Scientific Co., of Cliicago The crest of the north slope of the state is about thirty miles south of the shore of Lake Superior, is formed by the summit of the Penokee and Douglas ranges. In many places the slope is covered by the glacial cla\- so deeply that the underlying rock is not visible, but in other places the portion adjacent to the shore has been washed free from the glacial material and the sandstone stands out in wave- cut bluffs. The rivers running down this slope are slow and sluggish at their headwaters, but as they gain the edge of the slope they plunge down in a series of falls and rapids to the flat land along the shore; near their mouths many of them are again slow. Where they fiow over the soft sandstone they have cut deep gorges almost to the water's edge. Many of the streams have built up large delta deposits at their mouths over which they now wander through swamps and winding channels. The southern slope is long and very gentle, extending even into Iowa and Illinois. It is subdivided by a low and irregular divide into two parts; an eastern and a western. The waters of the western slope flow into the Mississippi and so 2,000 miles and more to the Gulf of Mexico; the waters of the eastern slope flow into Lake Michigan and to the St. Lawrence and the North Atfantic ocean, an even greater distance. Near the north line of the state is the Penokee Ridge, a long range of low hills which stand up above the surrounding country because their superior hardness has enabled them better to resist the attack of the weather; through the ridge from north to south is cut the Penokee Gap, where the Bad river finds its way from the swampy uplands to the shore of Lake Superior. The Penokee Ridge was formerly called the highest part of the state, but it is now known that the summit of Rib Hill, at Wausau. 1,940 feet above the level of the sea, is higher. From the highland of the north central part of the state the rivers run in a distinctly radial manner, giving a splendid illustra- tion of the "consequent" condition. South of the highland there is a broad lowland extending across the state in a crescentic shape from east to west. The crescent is broader in the middle and narrows towards either extremity. This is the sandstone area of Wisconsin and it owes its condition as a lowland to the rapid disintegration of the soft sandstone. The pres- ence of this lowland is of the greatest importance to the state, for it is here that all the waters of melting snow and rain enter the ground to appear farther south in the artesian wells for which the state is famous; nor does it cease there, for the artesian wells of the adjacent portions of Iowa and Illinois derive their supply from the same source. The eastern part of the state is divided between long ridges and lowlands parallel to the shore of Lake Michigan. The westernmost ridge lies along the border of the sandy lowland and separates it from a second lowland to the east in which lies Green Bay, the Lower Fox river, Lake Winnebago, Horicon Marsh, and the Rock river as far south as Watertown. This ridge is low and irregular and is crossed by several streams, notably the Fox and the Wolf rivers. It hardly anoears on the surface as a ridge and might easily be over- looked by one not aware of its presence; the glacial drift lies deep upon its surface and the rocks peep out only occasionally. The second lowland, which may well be called the Green Bay Lowland, owes its presence in part to the erosive action of rivers in pre-glacial time and in part to the action of the ice, which sent a long arm down this valley and deepened it and shaped it to its pres- ent form. The eastern side of the Green Bay Lowland is formed by the outcrop of a layer of heavy limestone which faces to the west in a steep bluff, but slopes very gently downward to the east. The upper surface of the eastern slope is covered by the glacial debris, so that the rock does not appear on the surface and there is a false appear- ance of abruptness in places; the great terminal moraine of the Green Bay peninsula lies on the gentle slope. On this gentle eastern slope the rivers flow to Lake Michigan; in many cases the accumula- tion of glacial debris causes them to run a considerable distance parallel to the shore before entering the lake. The southwestern part of the state is totally different from the eastern, the rocks lie nearly horizontal in the ground, and the rivers in cutting down their channels have not worked the land out into long lowlands and ridges, but have cut straight down through hard and soft alike as they came to it, and the course of the valleys is accidental. This has resulted in deeply incised valleys, which have cut the land up into isolated blocks of land of irregular form. The deep valley of the Wisconsin river cuts off a region of very rough land on the north from a less deeply dissected region on the south. The north edge of the plateau to the south of the Wisconsin river is the celebrated Military Ridge, along which ran the military road west from Madison; it is now occupied almost exactly by the Chicago and North-Western railroad. The most prominent blocks of the dissected plateau south of the Wisconsin river are between the Platte, the Sugar and the Pecatonica rivers. On the summit of these blocks lie the residual mounds, Blue Mounds, Platte Mounds, and the Sinsinnawa mound. These show the height to which the land reached before its degradation. WISCONSIN AS AN ANCIENT COASTAL PLAIN. The second of the models shows Wisconsin as an Ancient Coastal Plain, as described by Prof. W. M. Davis of Harvard. In a broad way the structure of the state is very simple; it consists of a central mass of hard igneous rock formed in the earliest geological period, the Archean. This central mass is surrounded on all sides by layers of more or less horizontal sedimentary rocks, shales, sandstones, limestones. etc. The central mass of hard rocks originally stood up as an island or peninsula in the ocean and the sedimentaries were deposited on the floor of the ocean around the island; they are made up of debris formed by the degradation of this or neighboring islands, in the adjacent parts of Canada, Minnesota and Michigan. The edges of all the continents today present a very similar appearance below the water line. They are surrounded by an area of imiPii^ Fig. 2. PHOTOf.RAPH of Modkl Showinc, Wisconsin as an Anciknt Coastai, Pl.ain Cut Furnished by the Central ScientilTc Co., of ChicaHfo 8 gradually deepening, shallow water which extends out from the wa- ter's edge for varying distances, but which terminate by a sudden deepening at about the point where the water reaches a depth of 100 fathoms (600 feet). The area of shallow water is known as the Con- tinental Shelf, the area of sudden deepening is called the Continental Slope, and the deeper portion of the ocean beyond, of an average depth of two and one-half miles, is referred to as the Oceanic Plateau. The Continental Slope is regarded as the true edge of the continent and the Continental Shelf is potentially a portion of the land, for it is elevated and depressed, geologically speaking, today and tomorrow, and the deposits upon it are the debris of the land. When a portion or all of the Continental Shelf is raised above the surface of the water the flat plain resulting is referred to as a Coastal Plain. Upon the Continental Shelf are deposited the sands, clays and limey muds that become the sandstones, shales and limestones of the Coastal Plain when the land is elevated. The deposits from the land rarely reach beyond the edge of the Continental Slielf and the "deeps" of the ocean are rarely raised to the surface to form land, so that there are few rocks that can be recognized as formed of deep water deposits. It is in this wise that all the sea coast portion of the eastern tier of states has been formed. The "Atlantic Coastal Plain," lying between the sea and the foot of the Appalachian Mountains, was at one time under shallow water and was built up of the debris from the degradation of the Appalachian Mountains, just as the bottom of the ocean adjacent to the present coast line is receiving deposits today. In the alternate elevations and submergences the State of Wiscon- sin went through much the same history as the Atlantic Coastal Plain; the seas surrounding the old Archean land mass were mostly so shallow as to be regarded as a Continental Shelf and on their bot- toms were laid down the debris from the land in the form of clays, sands and calcareous muds which, when the land was elevated, were hardened into the shales, sandstones and limestones of the state. The similarity of the origin and history between the State of Wis- consin and the Atlantic coast is very apparent; only our state passed through its history millions of years ago and the Atlantic coast has still to complete its cycle of development. Wisconsin has very prop- erly been described by Davis as an "Ancient Coastal Plain." A Coastal Plain may result from the elevation of the Continental Shelf in two ways. (1) Either it may be raised horizontally upward by a single direct movement of the earth, which will result in a flat expanse made up of horizontal layers of varying hardness; or, (2) it may be lifted by single or successive movements so that its inner landward end is higher than the outer; this will cause the layers to be tilted in the ground and the edges will appear on the surfaces as successive parallel belts. As soon as the Coastal Plain appears above the surface of the water it is exposed to the degrading forces of nature and the rivers begin to wear down into it. When the strata are tilted the edges of the hard and soft layers come to the surface alternately and the rivers cut down into the soft layers, leaving the harder ones standing up as ridges. The ridges thus formed with one slope short and steep and the other long and gentle are called "Cuesta" ridges. This is exactly what has happened in eastern Wisconsin and explains the presence of the ridges and lowlands. When the rocks are more horizontal the rivers cut straight down and there is an irrcgularitj'' of the topography, as explained above this is the condition of south- western Wisconsin. The layers of sedimentary rock which build up the state are from below upwards, the Potsdam sandstone of the Cambrian divi- sion of geological time, the Lower Magnesian limestone, the St. Peter's sandstone, the Galena and Trenton limestones, the Cincinnati shale of Ordovician time, the Clinton iron ore, and the Niagara lime- stone of the Upper Silurian time, and the Hamilton shale of the Devonian time. These show a notable alternation of hard and soft layers. Fig. 3. Cro.s.s Section of State from Superior to Milw.^ukee Showing Arrangement of the Strata The Potsdam sandstone, the St. Peter's sandstone, the Galena limestone and the Cincinnati shales arc softer, and the Archean crystallines, the Lower Alagnesian, and the Niagara limestone are harder. In accordance with the principles of erosion described above the tilted rocks of the eastern portion of the state have been sculptured into long ridges with their steeper faces toward the old land to the north and west and separated by lowlands; the horizontal rocks of the southern part have been sawn apart into isolated blocks. This gen- eral conception of the degradation of the state controlled by the structure of the underlying rock will enable the student to get a better understanding of the details of different portions. 10 The model shows the surface conditions broadly. The Potsdam sandstone lying directly upon the Archean rocks has yielded rapidly to the degrading forces and has been worked out into a broad low- land over the central portion of the state. The fact that the outcrop of this porous sandstone has been reduced to a lowland and that below the surface it slants away to the south and east below the impervious Lower ^lagnesian limestone, is the important and deter- mining factor in the presence of the artesian waters of the southern part of the state, and of Illinois and Indiana as well. This depressed area is the Inner Lowland of Wisconsin. Overlying the soft Potsdam sandstone is the harder Lower Mag- nesian limestone; formerly it extended much farther to the north, but a good portion has been removed in the making of the Inner Low- land. The outcrop of the limestone is a low cuesta ridge with its steeper face to the west and north. It does not show as a bluff on the surface because it is largely obscured by the covering layers of glacial drift, but its course is marked by the presence of a line of gently rising hills from the north side of which the limestone projects at intervals. The course of this ridge is through Marinette, Oconto, Shawano, Outagamie, Winnebago, Green Lake, and Columbia coun- ties. In the last named county the rocks have become nearly hori- zontal, so the rivers no longer recognize it as a determining factor in their course. North of the lower Wisconsin river, in the triangle between it and the La Crosse and Baraboo rivers, the Lower Magne- sian limestone appears capping the tops of hills of horizontal rock, but because of the horizontality the hills are isolated blocks, not continuous ridges. South of the Wisconsin the Lower Magnesian is covered by the rocks of higher formation and is nearly horizontal, but there is a slight dip to the south; this region is a distinct high- land, deeply trenched by the rivers which run over it in an irregular manner, for there is not slope enough to the rocks to determine their course, but on the north the edge of the highland is marked by a steep bluflf which faces to the north and overlooks the Wisconsin river which flows at its foot. The steep face has been formed by the Wisconsin river shifting slowly to the south, following the slight dip of the layers as it wore out its bed in the soft Potsdam sandstone. The crest of this bluff is the celebrated Military Ridge, so called be- cause of the military road that ran along in the early days of the state. It is marked today almost exactly by the course of the Chicago and Xorth-Western railroad from Madison to Dodgeville. This is the inner or first cuesta. Overlying the hard rocks of this cuesta are the softer rocks of the Galena limestone an<l the Cincinnati shales. In the eastern part 11 of the state these have been excavated into a long lowland parallel to the inner cuesta, running through Marinette, Oconto, Outagamie, Calumet, Winnebago, Brown, Fond du Lac, Dodge, Jefferson, Rock and Walworth counties. The course of the lowland is marked very plainly by the position of Green Bay, the Lower Fox river, Lake Winnebago, the Horicon marsh and the Rock river as far south as Watertown. As in the Inner Lowland and the First cuesta the north- ern end where the rocks are most sharply tilted is the most clearly defined. The valley of the Lower Fox river is excavated in the soft Cincinnati shales, so that it has very low walls on the west and the bottom is very broad, but the eastern side is marked by the abrupt cliffs of the steep face of the outer cuesta formed by the overlying Niagara limestone. The whole of the outer, or Green Bay, lowland has the same steep face of limestone from the extremity of Green Bay on the north to a point nearly west of Milwaukee on the south. The east shore of Green Bay is formed by a line of bluffs from 100 to 200 feet high on the average, but reaching as much as 400 feet in places; these bluffs are nearly vertical and have been sculptured by the weather into peaks and pinnacles, isolated crags and bluffs, that give to the shore a unique beauty. South of Green Bay on the east shore of Lake Winnebago and as far south as Horicon in Dodge county the outcrop of the limestone still forms a ridge though much reduced in height. It is traceable in the local names, Winnebago Ridge and "the ledge." Farther south the lowland area is less appar- ent and the ridge forming its eastern face becomes lower until in the town of Ashippun in Dodge county, about opposite Milwaukee, it dis- appears. The ridge, with its steep western face, is known as the sec- ond or Niagara cuesta; its eastern face is a gentle slope to the shores of Lake Michigan, although the surface appears far from gentle in many places, being covered by the highly irregular superficial deposits of the great terminal moraine. The slope gradually broadens from the northern point of Door county, where the waters of Green Bay and Lake Michigan meet, to the southern edge of the state, where it is about 40 miles wide. Far to the west in the Platte and Blue Mounds we have evidence of the former extension of the Niagara limestone over the southern portion of the state, for the tops of these mounds, many feet above the surrounding country, are capped with it and the underlying for- mations show in the sides of the mounds; evidently the rocks of the Niagara period at one time covered all the intervening part of the state and have been removed by the processes of degradation up to the present limits of the cuesta ridge. 12 THE MODEL REPRESENTING THE GLACIAL CONDITIONS IN WISCONSIN. A glacier is any mass of ice, consolidated from accumulated snow, that moves by its own initiation over the ground; usually it is of good size, but many masses of small size clinging to the sides of mountains have a motion which brings them within the definition. The motion is very slow, rarely exceeding a few feet a day (as much as 100 feet a day has been recorded, but this is regarded as highly exceptional). Chamberlin and Salisbury state that the ice cap of Greenland probably does not advance more than one foot a day on the average. The origin of motion in the masses of ice is an un- solved problem, but we know it does move, and moves in a manner comparable to that of a very viscous body. The best analogy is that of a barrel of tar which has been overturned on a warm day; the tar streams slowly from the barrel and drags itself stifily forward over the irregularities of the surface, but eventually accommodates itself to the surface as perfectly as water could and acts upon every inch of the ground. So with the apparently brittle ice; if it is given time it moulds itself in its slow advance to the most intricate irregularities and searches out every exposed surface for its action. Almost every problem of glaciology can be answered, (jualitatively at least, by imagining what would be the action of the flowing mass of tar over the same surface. For some reason, probably a combination of elevation of the surface and alteration in the composition of the atmosphere, the climate of the geological period just preceding the present was re- duced so much that great quantities of snow accumulated in several places in the northern hemisphere and slowly spread in all directions from these centers. It is a great mistake to suppose that the ice of the glacial time accumulated at the north pole and spread evenly to the south in all directions; instead the ice accumulated in distinct areas rather far south and spread north as well as east, west and south. In North America there were three such centers, an eastern just east of Hudson's Bay suoporting the Labrador ice sheet, a middle just to the west of Hudson's Bay from which spread the Keewatin sheet, and a western in the mountains about the same lati- tude, supporting a smaller, Cordillcran sheet. It is with the eastern- most of these, the Labrador sheet, that we have most to do, for, with a single and trifling exception it is the only one which entered the limits of the state. The advance of the ice over the state was in a manner very different from that usually pictured by students. We have seen that 13 it did not originate as a single cap at the north pole and advance uniformly to the south over all parts of the earth; neither did it advance with an unbroken front to its farthermost limits and then retreat. Its movement was rather a succession of advances and retreats, no single movement covering exactly the same ground as the others nor having the same extent to the southward. The differ- ent stages of advance have been called invasions and have received Fig. 4. Photo(;raph of thk: Model Illustrating the Glacial Conditions Cut Furnished by the Central Scientific Co., of Chicago names suggested by the states or regions in which they had their maximum development; thus six different invasions have been made out which are called the Alberton, Kansan, Illinoisan, lowan, Early Wiscrmsin and Late Wisconsin. It is the sum of these diflfercnt inva- sions that is spoken of as the Ice Age and the line joining the farther- most cxlt-nl <if LTieh and ail, is spoken of as the southern limit of the 14 ice. The criteria for distinguishing between two events so closely connected in time as two of these invasions are so obscure, involving the nice balancing of evidence furnished by the appearance of soils, the amount of erosion and the accumulation of vegetable debris that it is often beyond the power of any but the expert to determine the separation. The state was visited by at least two which have left recognizable the traces, an earlier invasion, perhaps the lowan or even the Kansan, and the last, the Wisconsin invasion. The forward movement of the ice over the state in the different invasions was not that of an irresistible mass with a straight unbroken front which overwhelmed everything in its path, but rather that of a plastic mass which accommodated itself to the surface and divided to pass around obstacles, doing its work of erosion in the softer rocks and leaving the harder comparatively untouched. In order to under- stand the form taken by the ice the structure and building of the state must be kept clearly in mind; as shown in the first two chapters, it is essentially a core of hard, crystalline rocks, which forms today the highest portion of the state, flanked by successive layers of alter- nately harder and softer rocks, which are so tilted that they outcrop on the surface in successive parallel ridges. Already before the glacial age the softer layers had been excavated by the rivers into lowlands and the harder layers stood up as cuesta ridges. Both the earlier and the later sheets were divided into lobes by the irregularities of the ground over which they passed, but the record of the first sheet is much obscured by the deposits from the last one, which passed over much the same territory. So far as can be made out the history of the two sheets is some- what similar. The ice of the first invasion advancing in a generally southwest direction from the point of its origin southeast of Hudson's Bay encountered the highlands of hard, igneous rock which form the main portion of northern Wisconsin and the upper peninsula of Michigan and at the same time entered the two great valleys which are now the beds of Lakes Michigan and Superior. As the advancing ice met the barrier of hard rocks, which it could not easily surmount nor remove readily by erosion, it was deflected down the convenient valleys in two great diverging lobes. The western one passed almost directly west through the basin of Lake Superior, probably giving it much of its present shape in its passage, and emerging from the west- ern end turned southwest again, and continued imtil it reached far south of the present southern line of the state. The eastern portion of the divided mass continued almost directly south in the basin of Lake Michigan and when well south of the state spread out to the 15 west until the edges of the two lobes met in the vicinity of Dubuque. During some portion of the invasion the ice succeeded in passing the highlands to the north and advanced as a short lobe over the central portion of the state as far south as Grand Rapids, approximately. The ice of the Wisconsin sheet has left a much clearer record in the form of striations on the rocks, moraines and altered drainage lines. Advancing from the northeast the ice was divided by the same elevated region of hard rocks as was the ice of the first invasion and split into a mass which passed down the Michigan trough and one which headed westward in the Superior trough. These separate masses probably found the guiding lake basins much deeper than did the first ice, for there is no doubt that though the ice felt the guidance of the preglacial topography it shaped and molded the hills and valleys as it passed. The large lobe that moved southward in the valley of Lake Michigan was again subdivided into smaller lobes; a larger which con- tinued straight south and is known as the Michigan lobe, and a smaller which moved somewhat to the southwest and is known as the Green Bay lobe. The ice of these two lobes extended down two pre- glacial lowlands, the Michigan lowland on the east and the Green Bay lowland on the west, and that they were divided on the north by the hard rocks of the Niagara cuesta, which projects out between Green Bay and Lake Michigan as the Door peninsula and can be traced farther north in Washington Island, Rock Island, Great Gull Island and a ridge which continues beneath the water and is revealed only by soundings. A small lobe extends from the western side of the Michigan lobe, near the southern border of the state; from its relation to the lake of that name it is known as the Delavan lobe. The Superior mass spread to west as in the earlier invasion, but the movement of the ice was so great that part of it was forced up the north slope of the highlands and down the other side; as it left the valley of Superior it encountered the hard rocks of the Bay- field peninsula, which divided it into two parts, just as the Door peninsula divided the Michigan lobe, the part to the east extended only a short distance to the south, invading the region which is now about the headwaters of the Chippewa river and has so been called the Chippewa lobe. The western portion of the Superior lobe ex- tended out of the western end of the Superior trough and turned southward as the Superior lobe; it covers portions of Minnesota, Iowa and Illinois, as well as Wisconsin. As in the case of the first invasion, the ^^lichigan and Superior lobes passed around the southern end of the state, and the middle, Chippewa, lobe did not reach far 16 south of Wausau, so that the southwestern corner of the state has never been touched by the ice, though it is well within the limits of the glaciated portion of the United States; this is the celebrated Driftless Area of Wisconsin. Another lobe of glacial ice just touched the borders of the state on the west, in the vicinity of St. Croix Falls, but this one was very different in origin from those which covered most of the state, for it had its birth in the great Keewatin sheet, which developed west of Hudson's Bay and advancing to the south covered the state of Min- nesota, North Dakota and South Dakota. The portion of this sheet, which advanced across Minnesota to the border of Wisconsin, is sometimes called the Minnesota lobe and sometimes the Red River lobe. This lobe of the western ice sheet and the Superior lobe of the eastern sheet met on the line between the states of Wisconsin and Minnesota and have left their recoras in mingled confusion. The Terminal INIoraine in Wisconsin is quite generally referred to as the Kettle moraine. As would be expected from its origin, the topography is rough and irregular in the extreme; sharp, steep-sided hills alternate with deep, steep-sided holes which have no outlet and may contain ponds or swamps or be entirely dry. There is no regu- lar arrangement in lines or otherwise of the hills and valleys and the drainage is very imperfect; every feature tells of the violent origin. The deep, steep-sided holes appeared to the first describers to re- semble the large kettles used in the early days in making lye and soap, and so they were referred to as the "Potash kettles" or "kettles" and the name gradually spread to the whole ridge. The moraine enters the state from Illinois in Kenosha county, not far from the lake shore, and extends slightly west of north to the vicinity of Burlington, where it turns sharply to the southwest, mark- ing the position of the division of the Michigan glacial lobe called the Delavan lobe; completing the small semicircle in Walworth county around Lakes Geneva and Delavan, which marks the extent of the Delavan lobe, the moraine of the ^Michigan lobe joins that of the Green Bay lobe just north of the village of Richmond, Walworth county,, a few miles south of Whitewater. From the point of union a strong ridge runs northeast across the state almost to the ex- tremity of the Green Bay peninsula. From Richmond the Green Bay moraine runs almost straight north to a point a few miles northeast of Antigo, in Langlade county, where a sharp re-entrant angle marks the union of this moraine with that of the Chippewa lobe. As in the case of the Lake Michigan and Green Bay moraines a ridge runs back northeast from the point of union, marking where the sides of the two lobes met. The terminal moraine of the Chippewa lobe extends 17 south and west in a great curve through Lincoln and Taylor counties until it meets the moraine of the Superior lobe in Washburn county. Here again a re-entrant angle and a northeasterly projecting ridge marks the meeting of the sides of the two lobes. The moraine of the Superior lobe passes southwest and out of the state in the southwest corner of St. Croix county. The origin of the Green Bay and Lake Michigan lobes has already been described and the influence of the preglacial basin of Lake Michi- gan and the Green Bay lowland in directing their course pointed out; but while the main motion of the lobes was to the south they were at the same time expanding in a less degree to the sides, so that the two lobes were overriding the sides of the channels which directed them. As the sides of the lobes advanced in a direction more or less at a right angle to the main motion they gathered in front of them and pushed ahead a terminal moraine in all respects identical in char- acter with the terminal moraine at the front of the lobe; as the two lobes expanded, one to the west from the basin of Lake Michigan and one to the east from the valley of Green Bay, the two sides and the moraines ahead of the sides came together near the middle of the Green Bay peninsula and farther south to the point where the ter- minal moraines meet at Richmond. Because of the origin of this branch of the kettle moraine it has been called an Interlobate mo- raine. As shown above, interlobate moraines also mark the line of meeting of the Green Bay and Chippewa and the Chippewa and Su- perior lobes, but neither of the two is so well marked or preserved as the one in eastern Wisconsin. On the western side of the state there is a considerable area be- tween the terminal moraine and the driftless area which is occupied by deposits from the ice of the earliest invasion. There are here all the features of the drift-covered region, but in a much modified form, for they are much older and the forces of degradation have been much longer at work upon them and have reduced them much farther toward the original condition. The shape of this region shows that it was covered by a lobe of the ice very similar to the Chippewa lobe of the last invasion; its terminal moraine leaves the terminal moraine of the last invasion somewhere north of Wausau and runs southwest into Clark county and then curves northwest into Chippewa county and southwest again into Pierce county and so out of the state. A somewhat similar area appears in the extreme southeastern part of the south of the terminal moraine of the Green Bay lobe of the Glacier. The Driftless Area. — This lies in the southwestern and western parts of the state and includes narrow strips of the adjacent parts of 18 the states of Illinois, Iowa and Minnesota. Its northern edge is indented by the convex terminal moraine of the region of earlier drift and on either side of this it sends sharp processes to the north. Its general outline is shown in figure 4. Surrounded on all sides by glaciated country, it furnishes to the student of the state and of glaciology in general a mass of most valuable comparative material, for it shows the topography of an older land in an advanced stage of degradation immediately adjacent to regions which in the latest geological period has been covered by new deposits, now in the ear- liest stages of degradation. It is impossible to even list the theories that have been advanced to explain why this region was not visited by the ice, so that only one, that advanced by Chamberlin and quite generally accepted, will be reproduced here. The driftless area lies between the great depression of the Lake Superior basin on the north and that of the Lake Michigan basin on the east, with the highlands, composed of hard, crystalline rocks, directly to the north and northeast. Lake Superior has an average depth of about 1,000 feet; its surface is about 600 feet above the level of the sea; the summit of the highlands 30 to 40 miles to the south is about 1,200 feet above the level of the lake, so there is a difference of about 2,200 feet from the bottom of the lake basin to the top of the highlands. Lake Michigan has an average depth of 900 feet and its surface is nearly on a level with that of Lake Superior, so there is a difference of about 2,100 feet from the bottom of the lake to the summit of the highlands to the west. If the lakes were drained it is seen that the highlands would constitute a very considerable eleva- tion between them with a long slope to the south, including most of the state of Wisconsin and good parts of the rreighboring states of Illinois, Iowa, Missouri and Minnesota. It is probable that the ice advancing from the northeast was split by the hard rocks of the upper peninsula of Michigan and advanced around the highland in the form of lobes which clung to the depressions of the lake basins, but in the forward movement the ice was gradually crowded up and over the obstructing highlands, and in the time of the maximum for- ward movement of the ice crept down the face of the southern slope in what is called the Chippewa lobe. But why, having once surmounted the barrier, did not the ice descend the southern slope as rapidly and as far as the Michigan and Superior lobes? Perhaps for two main reasons. According to Chamberlin the ice surmounted the barrier, 2,100 to 2,200 feet high, only when it was at its greatest advance, and from then on its forward movement was less rapid; moreover, the forward movement of the ice was greatly retarded as it pushed over the hills and was much slower than that of the other 19 lobes. Again the maximum of forward movement was coincident with the culmination of the Ice age, and thereafter the climate became slowly warmer; the ice, creeping down a long southern slope, was exposed to the full power of the sun and it is probable that the rate of melting was faster there than on the other lobes and faster than the rate of advance. The stronger Superior and Michigan lobes did not waste by melting so rapidly because, instead of being thinned by spreading out, they were more confined in the narrower basins and thickened by accumulation, so that they advanced more rapidly than they were destroyed by melting. It is also probable that the lobes assisted in their own perpetuation, for large masses of snow or ice, by chilling the air which blows upon them, induce an increased pre- cipitation; so these lobes may have chilled the moisture laden air from the south or from the driftless area and caused abundant snow- falls upon their surface. Says Chamberlin: "Divided by the Highlands, led away by the valleys, consumed by wastage where weak, self-perpetuated where strong, the fingers of the mer de glace closed around the ancient Jardin of the Upper Mississippi valley, but failed to close upon it." These models are made by the Central Scientific Co., of Chicago, 14-28 Michigan street. Information regarding them may be obtained from Mr. Case, or from the Central Scientific Company. 1 i b iJjs> As iUtLt-S. CALlF. Lithomount Pamphlet Binder Gaylord Bros. Makers Syracuse, N. Y. AA 000139 946 8