GEOLOGY. Geology as an agency in the for mation of soils is an interesting study to the farmer. By it he may not only form a definite opinion as to the nature of the soil, by knowing what earths are produced by the decomposition of certain rocks, and the elements of which they were composed, and the study is interesting as showing the various agencies in nature used in the formation of soils, and especially in the for mation of western soils. Hon. James Shaw, of Illinois, some years ago, when more actively engaged than now in studies relating to the soil and soil uses, in an address before the Illinois State Horticultural Society, well and accurately elucidated the subject of geology, as relating to the origin and formation of soil, the district of country referred to being rich in various strata, and in its diversity of soil. Speaking of that part of Illinois lying north of the old Silurian beach, which crosses the State from a, point near Hampton, north of Rock Island, on the Mississippi river, and passes eastward, a few miles south of Ottawa, bending up a little north of Morris, and passing on to the eastern line of the State, south of Chicago, says: The land north of this Silurian beach was compara tively elevated table land at the time the coal deposits of the great coal basin lying south of this old beach were in process of formation. And there is evidence that over this comparatively elevated table land a great denudation has taken place. Sonic great force has worn off and swept away, from southern Wisconsin and Northern Illinois, a large amount of material, which has been deposited over the face of the country south and west of that elevated region. It is estimated by Prof. Whitney and other good geological authori ties, that at least 300 feet has been denuded and carried away in the region of the Illinois and Wisconsin mounds. These mounds—Scales mound, the Blue mounds, Terrapin ridge, and the various elevated and island-like elevations left over the general level surface of that part of the State north of this old Silurian beach are mountains left standing when the rest of the formation was swept away. Any one with thoughtful mind, who stands upon their tops and looks over the surrounding country, or who examines the regular succession of outcrops up their sloping sides, can not resist the conclusion that the general level of the whole country sur rounding once eorresponded with these highest points. As in reading a book, we at once miss the pages which are torn out, so in examining these mounds, we at once miss whole leaves and parts of leaves in the Great Stone Book, which have been removed by the forces of which I shall presently speak. The Galena Limestone, the Cincinnati Group, and the Niagara Lime stone, are the leaves, whose fragments yet remain to attest a time when each one of them in regular succession spread over the region now under •discussion. Against this Silurian beach the coal measures are shingled, as it were, or deposited. At Ottawa, IIL, the old St. Peter's sandstone shines like sugary masses along the river banks, and is elevated in fantastic shapes at Deer Park and Starved Rock, a little to the northeast; but at LaSalle, a few miles southwest, coal pits are sunk for hundreds of feet, and the black treasures of the earth found in the greatest abundance. At Sublette the Galena limestone is the bed rock nearest the surface; but at Princeton, toward the south and west, an artesian well, five hun dred feet deep, still exhibits coal measure deposits. This shows that this old Silurian beach, in the carboniferous ages of the world, presented the appearance of a somewhat abrupt range of hills across that part of the State. Over that part of the country north of this beach, the bed rocks are covered with superficial deposits from ten to fifty or one hundred feet in thickness, composed of clays, sands, loams, gravels,• drift materials, and prairie soils of later growths. If this super incumbent mass should all be removed, leaving the naked bed rocks, the general face of the country as to levelness of appearance, would not vary much from the present state of things. In classifying the soils in this Roek river district, we find several well marked varieties. The alluvial deposits of the river bottoms are latest in formation, and deserve a brief notice. In examining river deposits, the first thing worthy of consideration is the flood bed. Here the action of the river is that of currents, or flowing water. Where the current runs strong, sand will be thrown up in tow heads, and sand banks, and sand islands; in the still places a fine black mud will be deposited ; and this force will exert a sifting and assorting influence, and form mud flats and banks, and deposits of pure sand. The next action of the river will be over its flood plain, or that part of its bed covered only by the high water of the spring inundations. This is usually a low bottom, covered at the flood of the river with water, and producing a heavy crop of sour prairie grass later in the season. Over this the water usually rises and falls without much current action, and a yearly Nile-like detritus, or fine mud, is precipitated. The soil thus formed is fat, deep, and sour, and is unfit for agrieul. tural and horticultural purposes, until it has been built up beyond the influence of the river floods, and sweetened by the sun and atmos pheric influences. Then it becomes a soil of inexhaustible richness and productiveness. Step ping backward in geological time, we next come to the old river terraces, which are simply the ancient flood-beds and flood-plains of these same rivers, at a time when they rolled an infinitely larger volume of water to the sea. Over these are the sandy soils, and the rich, flat bottom lands, Nile-like in their inexhaustible produe tiveness. The Mississippi river, Roek river towards its mouth, and many of the smaller interior streams present these well known river phenomena; and make a notice of these alluvial deposits, and this fluviatile action necessary in speaking of the soils of the State. Receding -backward in geological time, we come to the bluff formations, the oldest deposits of the Quaternary system. This is called the Loess, or Bluff formation. It is not extensively devel oped in Northern Illinois, but is present in most of the bluffs which skirt our streams. Deep rooting trees and vines find in it a congenial soil, and the best soil conditions of growth. Some of these Loess or partly Loess formations in our part of the State would be the best fruit and wine producing districts in the world if kindly Italian skies and genial atmospheric eon ditions smiled on the tops of the trees and vines. When the Mississippi and the Illinois rivers were lake-like in their expanses, and the waves beat up against their bluff shores, throwing up silt, oozy detritus, and frothy marls and sand, this bluff formation was deposited and accumulated. It is composed of light cream colored clays, greenish marls, muddy sands, and various com binations and mixtures of these; and, as already intimated, it affords the best soil conditions in the State, or in the world, for the growth of the vine and all kinds of fruit trees. Even in our chilling and unfavorable climate, fruit and grapes of fine appearance and good quality are begin ning to be produced in considerable abundance. At Galena, Morrison, Mount Carroll, and Ster ling, I have seen small vineyards purple with their great crops of generous fruit, and orchards laden with the finest of our hardier apples; while the strawberry, raspberry, gooseberry, cherry, and other kindred fruits are raised in the greatest abundance, and of good quality. Next to the Loess in succession are the regular soils and clayey deposits which cover the uplands or general prairie level of the country. Aud inasmuch as these are originally derived from the decomposition of the rocks, it will be well to call attention to the character' of the bed rocks in this part of the State. If the dirt mantle covering these rocks, in that part. of the State now under consideration, was all stripped off, the rocks then exposed would he found to belong to the Galena Limestone, Cincinnati Shales, and Niagara Limestone, coming to the surface in irregularly shaped patches. Now, the soil or earth mantle covering these rocks, notwithstanding the tremendous mixing to which they are sub jected by the drift forces, to be spoken of here after, partake somewhat of the nature of the depos its lying immediately beneath it, and were in part derived from their decomposition. The evidences of this are strikingly manifest. The Galena Limestone and Niagara Limestone, although separated by an intervening formation, are strik ingly alike in lithologieal character. Both are a coarse grained, cream colored and -reddish mag nesian limestone When they decompose a rather coarse grained soil is the resultant. In many • • places, if we dig from the surface to these rocks, we find a coarse, reddish, hard pan, or crumbly clay, resembling closely these rocks. As we sink into this clay we find pieces of float mineral and bits of the rock itself, the latter lying evidently in situ, unworn by water, and appearing like pieces of the original rocky mass, which was harder and had resisted the surrounding decay and rotting away of the rocky ledges. On the other hand, portions of the country underlaid by the Cincinnati Shales are covered by a close grained, finely comminuted, greenish, creamy col ored subsoil, closely resembling in texture and Ethological character the Shales from which it has evidently been derived. But these resem blances of the earthy mantle to the rocks lying under them are only found in certain localities in and around the lead basin; and only to that extent is the basin a driftless region. But the Lead Basin is not a driftless region. In many places around it and througlo. it evidences of .true northern drift are found. Bowlders are not rare in these places; float or drift copper is fre quently found; drift clay exists, regularly strati fied, and old river terraces may be traced, and modified drift and gravel is not rare. The lead region seems to have been only partially invaded by the drift forces, and these forces seem to have acted in a modified form. The heavy denuding forces spoken of already acted before the drift period. Then came on the drift conditions and the glaciation of the during which the transportation of clays and soils and a universal mingling and mixing of the surface materials of the earth took place, modified in the lead region in the manner just noticed. Soils and clays and sands in the first place, are derived from the decomposition of the rocky formations at and near the earth's surface. The processes of nature to-day, as in past geological ages are grinding rocks into soils and re-cementing and hardening soils into rocks. There was a time when the surface of the earth was covered with rocks, and rocks only, but atmospherical and chemical agencies, the solvent power of water, dews, and damp ness, and aqueous forces kept in constant action processes of slow decay, and soils were gradually formed and carried as sediments into ancient seas. We all know the old adages about the con stant dropping which wears holes in the stones; and the files of time, which wear and make no noise; but few realize bow important a part these peaceful agencies have played in the creation of the present order of things. The frost and the rain, the dissolving power of water and the mighty power of freezing and cold, and other like agencies and energies of nature are all pow erful to bring about the mightiest results. The tooth of time, gnawing away age after age, will nibble into clay and sand, the solidest rocky ledges. If undisturbed by mechanical forces, the superficial clays, loams, sands, subsoils and soils covering the underlying rocky masses, would be nothing but the residuum left after the re moval by percolation of water of the more solu ble portions of the decomposed rocks. The soil would then be in situ. Regions of country under laid by sandstone would be covered with a sandy soil; limestone districts would be covered with a soil with a limestone base, and the geologists could tell at a glance from the appearance of the soil, what rocks lay beneath it, and vice versa. But certain forces of nature transposed, mixed and mingled into one mass the materials derived from widely separated sources. The first of
these forces arc the same silent, peaceful agencies which we see operating round us in our daily walks over the earth's surface. There is a struggle going on all the time in our fields, in our streets, and everywhere, building up and tearing down, construction and destruction, an ever bal anced antagonism. Gentle rains and earth-born torrents, little trickling rills and strong streams are tearing down the soil from the hill sides and bear ing it away to the lower levels. The small water plowed trench of to-day, next year becomes a chasm, and ages hence a hollow, and the trans ported materials have been built up in alluvial deposits, or are the fillings in in the bottom of some stream. Alternate freezing and thawing helps along the varying struggle, and God's great plowshare, the frost, runs annually through the surface, mellowing the whole. These familiar, always acting, somewhat silent agencies, in time produce great results. They mix the soil, they transport it to some extent, but they never carry it long distances from its place of origin, nor do they carry the heavy masses of the drift materials for hundreds of miles away from their parent ledges. Other and mightier forces did this, and while doing it, they ground the stones into clays, and the clays into impalpable powder, as the wheat kernels are ground into superfine flour between the upper and nether mill stone. They were the mills of the gods, which ground exceed ingly slow, but ground exceedingly small. There was some tremendous force, which tore the bowlders from their parent out-crops in the dis tant Lake Superior regions, and drifted them on their journey to the South; which grooved and planed the surface of the solid rocks, and strewed for hundreds of miles in its track beds of clay and sand and gravel, and mingled, mixed, transported and reformed the soils to such an extent as to well-nigh destroy their separate char acteristics and origins over large portions of Northern Illinois, and greatly increase the diffi culty of their proper classification. This force, whether floes and bergs of ice, loaded with stones, gravel and detrital matter, and borne along by winds and currents, or strong, earth-born water torrents, moving along and wearing the abraded materials, or the slow procession of the all-power ful, crawling glacier—whatever it was, it moved like a vast army of shovelers,multiplied millions of tons of the loose materials denuded and worn down from the rocks of the north, and piled them like a thick earth mantle over the coal basins to the south and west. Of that great force I pro pose now to speak. In order to understand what that force is, it will be necessary to refer .to the well-known action of ice and snow in the glaciers of the polar world. It bas been shown that the struggle of the rain drop to get back to its mother the sea, produces the silent, peaceful agen cies and energies of nature. The struggle of the snow flake to get back to its mother, the same sea, produced those mighty drift forces whose results are so evident around us. Agassiz, Tyndall, Forbes, and other trustworthy scientific travelers, have made us familiar with the action of the ice forces as they now exist in the Alpine glaciers. Away up in the mountain basins of the Alps snows accumulate in vast fields and in great thickness. When the mass becomes heavy and thick, pressure changes the bottom of the mass into a plastic, porous sort of ice. This basin is the Mer de G-., A or sea of ice. Inasmuch as snow is constantly being added to it, the volume and thickness of this sea of ice would soon become so great as to produce serious consequences if some safety valve was not found to afford vent to the pent up mass. The lower part takes upon itself a slow, almost imperceptible motion, and soon fills the descending valleys with a stream or river of ice. As snow is added at the top, it sinks down to the bottom, and when it becomes ice, is drawn off, as rivers run out of lakes. This ice river flows slow, but is subject to all the laws of flowing water. It widens, it contracts, it deepens where the flow is slowest, and its motion increases where the mass passes over rapids. As it crawls down in its slow, irresistible motion, dirt hands are formed along its margins, stones and great masses of rock roll down upon it, the bottom and sides of the channel are grooved, planed and striated by the mighty power of the grinding, rubbing ice, and all the material accu mulated is carried eventually to the lower end of the glacier, and there dumped off in terminal moraines and huge piles of gravel, howlders, and other drift materials. In the case of the Alps, the glaciers melt when they reach the plain and before they find the sea, and glacier-born torrents begin where the ice ends, and the materials borne thither by the ice are further moved and assorted by the muddy, rushing waters which take their place. The struggle of the snow-flake has ended, and the struggle of the rain-drop now begins. Both are trying to get back to their mother, the sea. It is true the ice river flows infinitely slow, but in comparison with the river of water it moves infinitely strong. The Mississippi, if it were a glacier instead of a water river, could bear upon its back bowlders and whole ledges of stone as readily as it now floats a feather or a saw log. What it lacked in motion, it would make up in the slow, irresistible and mighty force of its all grinding, all consuming procession. Such is a glacier in the Alps, and these glaciers are knead ing certain parts of Italy over now as in past time they kneaded North America. Over the new Wrangell's Land and in Greenland the same forces of the ice are in active operation, only to a much greater extent. All upland Greenland is one vast Me?' de glace. But the Greenland glaciers, instead of melting in intermediate sunny valleys, push down into the sea itself, and after crawling along its bottom in the indenting bays and fiords, keep breaking off great masses, which float away in the deep blue waters until they are caught by wind currents and gulf streams, to be borne by them as icebergs and ice floes, whither the drift of the ocean carries them. And thus they float, until warmer seas cause them to melt in sunnier climes, and the floor of the ocean is strewn with their adhering dirt and stones. Certain iceberg paths in the sea already are accumulating at the bottom of the waters fields of bowlders and huge win drows and beds of gravel and dirt. Baffin's Bay, Hudson's Bay, and other northern seas and bays thus become nests of icebergs, and these icebergs before reaching the water, were glaciers, and these glaciers, at their origin, were the arctic snows of Greenland. Thus Greenland, like all other polar and circumpolar lands, is shipping her bowlders and her gravel to the bottom of distant oceans, and these, at some time in the future eternities of God, will become the face of continents. But we will come down to the prairies of Illinois. Start ing with the.bowlders in the neighborhood of Lake Superior, we trace them south and west to the Missouri river. These crystalline sandstones, fl ame colored granites and black-trap rocks, can be traced back to their parent ledges about the start ing, point. As we advance away from the parent ledges, the bowlders become smaller, and the drift materials towards the Missouri river are only gravels and drift clays. On seeing these curious water-worn stones strewn over the face of the country, the most ordinary mind at once concludes that they did not grow there, but were brought there from some other place. They are nigger heads, lost rocks, wanderers away from where they originally existed. They are entirely unlike any rocks outcropping round them, or in that region, and it is no great task to trace back the track over which they came. The world was lately excited over the Cardiff Giant, but men went to work and soon traced it back thousands of miles to its original bed in the gypsum quarries of Fort Dodge. In the same way they trace the bowlders back towards Lake Superior and Greenland, and could find the origin of each one if a few thousand dollars, or a large humbug, were involved. In some parts of Iowa these loose stones, from the size of a man's fist to that of a shock of wheat, lie so thickly strewn over the ground and accumulate round the margin of the lakes to such an extent, that in the one case parties might walk over them, stepping on the bowlders alone ; and in the other, they have give rise to the superstition or belief in walled lakeszl. In looking over a field of these bowlders once upon a time, my companion, who was somewhat irreverent, exclaimed, that it seemed to him as if the devil, when he sifted the soils down out of his great sifter, had emptied with a jerk the accumulated stones over this particular field. If; he had named the Creator, instead of his satanic majesty, I would have thought the comparison_ a good one. Now, I believe the ice cap which covers Greenland at the present time once• extended down into the middle regions of North America. Agassiz, some years ago, demonstrated to the satisfaction of the scientific world, that a great ice cap did cover the drift regions of the American continent. The carboniferous summer slowly ended, and the glacial winter as slowly came on. An entire change of the flora and fauna of these parts of the earth took place. Glaciers covered our land in every favorable locality. Seas of ice accumulated in the basins. Stones were torn away from the outcropping ledges: ledges were ground into sand and clay;. motion took place in various directions ; but the general movement was towards the south and west. As the climate again grew warmer, the ice cap slowly melted, commencing at the south and melting the ice towards the north. Basins became filled with water, and lakes and seas existed, into which glacial-born •currents of muddy water poured, and in which icebergs and floes floated, as wind or currents drove them. And we thus have the compound forces of the glacier, the iceberg, and the water torrent in vigorous operation. These causes, added to and coming after the peaceful agencies and influ ences, spoken of in the early part of these remarks, explain all that we see, while examining the drift formations, with which our Illinois rocks are covered. The peaceful causes which worked before the drift have also worked since the drift period, and produced some of the later phenomena observable. On pages 392 and 393 will be found a geological map of Iowa, Missouri, Illinois, Indiana, Ohio and Kentucky, and on pages 396 and 397 a geological map of Minnesota, Wisconsin and Michigan, which will present a fair view of the geological forma tion of an important region of the great Missis sippi valley, comprising as it does the great grain, grass and stock region of the United States. The explanation of the geological terms used are as follows: Alluvium. Deposits of earth, sand, gravel, and other tran-porced matter, made by rivers, floods, or other causes, upon land not perm nently submerged beneath the waters of lakes or seas.
Tertiary. The first period of the mammals, or of the Cenozoic era.
Cretaceous. Having the qualities of chalk; abounding in chalk.
Coal Measures. Strata of coal with the attendant rocks. Subcarboniferous. Carboniferous formation, the series of rocks (including sandstones, shales, limestones, and conglomerates, together with beds of coal), which make up the strata of the carboniferous ace or period. The prefix Sub signifying under or below, and includes in the map the millstone grits.
Devonian. Pertaining to certain strata which abound in Devonshire, Eng.; of, or pertaining to their age or for mation.
Silurian. A term applied to the earliest of the Palaeo zoic ages, and also to the strata of the age. Tee strati 1 Silurian, Upper ana Lower.
Metamorphic. Pertaining to, or exhibiting, certain changes which minerals or rocks may have undergone since-their original deposition.
Triassic. Pertaining, or corresponding to the saliferous hells or new red sandstone of Great Britain.
Eozoic —Azoic. The age preceding the existence of animal life, or anterior to the Silurian.
Igneous. Resulting from the action of fire; as lavas and basalt are igneous rocks. (See also article Soils.)