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The Rivers and Topography of the State are based upon and correspond with its geological formations. The surface, inclination and the direction of the interior drainage faces the southwest. Rock river, flowing southwesterly through one of the most beautiful and fertile regions, enters the Mississippi just below the Upper Rapids. The Desplaines, rising in Wisconsin west of Lake Michigan, and flowing southward, and the Kankakee, rising in Indiana, south of the lake, and flowing westward, form the Illinois. The latter stream, the largest in the State, courses across it in a southwesterly direction and falls into the Mississippi not far from the city of Alton. The Kaskaskia rises near the eastern boundary of the State and the 40th parallel of latitude, flows in a southwest direction, and forms a junction with the Mississippi not far from the town which bears its name. These and other smaller streams flow through valleys originally excavated in solid limestone by ancient rivers anterior to the formation of the drift. The latter material was subsequently deposited in these primitive water courses from 10 to more than 200 feet in thickness, and now forms the channel of the existing streams. For the formation of these ancient river beds of such great width and frequently excavated several hundred feet in hard carboniferous rocks, the diminished waters now flowing within their lining of drift are wholly inadequate. Furthermore, the alluvial valleys which the rivers now occupy are far too broad to correspond with the present volume and swiftness of the waters. The alluvial bottoms of the Illinois are nearly equal to those of the Mississippi, though the latter has a current twice as rapid and a quantity of water 6 times as large as the former stream. The smaller streams of the State occupy valleys filled with drift, through which the waters have been unable to cut their way to the ancient troughs below. Owing to this, the stratified rocks in many localities have never become exposed, and it is difficult for the geologist to determine the character of the underlying formations.

Though the surface of the State is generally level or slightly undulating, there are some portions of it considerably elevated. The highest summits are found along the northern border between Freeport and Galena, known as the mounds. The culminant points of altitude are 200 feet above the surrounding country, 575 above the waters of Lake Michigan, 900 above the junction of the Ohio and Mississippi, and 1,150 above the ocean. The tops of the mounds coincide with the original elevation of the surface, and their present condition as isolated hills is due to denuding

forces which have carried away the surrounding strata. Mounds occur in other places, some of them having a hight of 50 feet, and frequently a crown of timber upon their summits, which gives them the appearance of islands in surrounding seas of prairie verdure. Besides the mounds there are in the State 5 principal axes of disturbance and elevation. The most northerly of these enters it in Stephenson county, crossing Rock river near Dixon, and the Illinois not far from LaSalle. On the former river it brings to the surface the St. Peters sandstone; on the latter, magnesian limestone, a Silurian formation. At LaSalle the coal strata are uplifted to the surface from a depth of 400 feet, which shows that the disturbance occurred after their formation. On the Mississippi, in Calhoun county, there occurred an upheaval of the strata, attended with a downthrow of more than 1,000 feet. On the south side of the axis the Burlington limestone of the subcarboniferous series had its strata tilted up almost perpendicular to the horizon. On the north side the St. Peters sandstone and magnesian limestone were elevated, and form the bluff known as Sandstone Cape. This bluff, at the time of its elevation, was doubtless a mountain mass of 1,500 feet in hight, and has since been reduced to its present altitude by the denuding effects of water. The same axis of disturbance, trending in a southeastern direction, crosses the Illinois 6 miles above its mouth, and farther southward again strikes the Mississippi and disappears in its channel. Farther down the river another uplift dislocates the strata near the southern line of St. Clair county. This disturbance extends by way of Columbia, in Monroe county, to the Mississippi, and brings to the surface the same limestone and the St. Peters sandstone. Again, farther southward, an uplifted mountain ridge extends from Grand Tower, on the Mississippi, to Shawneetown, on the Ohio; on the west of the Mississippi it brings the lower Silurian rocks to the surface; in Jackson county, Illinois, it tilts up the Devonian limestone at an angle of 25 degrees; and farther eastward the subcarboniferous limestone becomes the surface rock. The last important point of disturbance occurs in Alexander county, constituting the Grand Chain, a dangerous reef of rocks, extending across the Mississippi and forming a bluff on the Illinois shore 70 feet high. Passing thence in a southeastern direction, it crosses the Ohio a few miles above Caledonia, in Pulaski county.*

The Formation of the Soil is due to geological and other physical agencies. From long habit we are accustomed to look upon it without considering its wonderful properties and great importance in the economy of animal life. Not attractive itself, yet its productions far transcend the most elaborate works of art; and having but little diversity of appearance, the endless variety which pervades the vegetable and animal kingdoms springs from its prolific abundance. Its mysterious elements, incorporated in the structure of plants, clothes the earth with verdure and pleasant landscapes. They bloom in the flower, load the breeze with fragrant odors, blush in the clustering fruit, whiten the fields with harvests for the supply of food, furnish the tissues which, wrought into fabrics, decorate and protect the body, and yield the curative agents for healing the diseases to which it is subject. From the same source also proceed the elements which, entering the domain

*Geological Survey of Illinois, by A. H. Worthen.

of animal life, pulsate in the blood, suffuse the cheek with the glow of health, speak in the eye, in the nerve become the recipients of pleasure and pain, render the tongue vocal with music and eloquence, and fill the brain, the seat of reason and throne of the imagination, with its glowing imagery and brilliant fancies. But while the soil is the source of such munificent gifts, it is also the insatiable bourne to which they must all return. The lofty tree, spreading its vast canvass of leaves to the winds, and breasting the storms of a thousand years, finally dies, and undergoing decomposition, enriches the earth in which it grew. The king of beasts, whose loud roar can be heard for miles, and whose immense power enables him to prey upon the denizens of his native jungles, cannot resist the fate which at length consigns his sinewy frame to the mold. Even the lord of the lower world, notwithstanding his exalted position and grasp of intellect, must likewise suffer physical death and mingle with the sod that forms his grave.

The soil was originally formed by the decomposition of rocks. These, by long exposure to the air, water and frost, become disintegrated, and the comminuted material acted upon by vegetation, forms the fruitful mold of the surface. When of local origin, it varies in composition with the changing material from which it is derived. If sandstone prevails, it is too porous to retain fertilizing agents; if limestone is in excess, it is too hot and dry; and if slate predominates, the resulting clay is too wet and cold. Hence it is only a combination of these and other ingredients that can properly adapt the earth to the growth of vegetation. Happily for Illinois the origin of its surface formations precludes the possibility of sterile extremes arising from local causes. As we have stated before, almost the entire surface of the State is a stratum of drift, formed by the decomposition of every variety of rock, and commingled in a homogeneous mass by the agents employed in its distribution. This immense deposit, varying from 10 to 200 feet in thickness, required for its production physical conditions which do not now exist. We must go far back in the history of the planet, when the Polar world was a desolation of icy wastes. From these dreary realms of enduring frosts vast glaciers, reaching southward, dipped into the waters of an inland sea, extending over a large part of the upper Mississippi valley. These ponderous masses, moving southward with irresistible power, tore immense boulders from their parent ledges and incorporated them in their structure. By means of these, in their further progress, they grooved and planed down the subjacent rocks, gathering up and carrying with them part of the abraded material and strewing their track for hundreds of miles with the remainder. On reaching the shore of the interior sea huge icebergs were projected from their extremities into the waters, which, melting as they floated into warmer latitudes, distributed the detrital matter they contained over the bottom. Thus, long before the plains of Illinois clanked with the din of railroad trains, these ice-formed navies plowed the seas in which they were submerged, and distributed over them cargoes of soil-producing sediment. No mariner walked their crystal decks to direct their course, and no pennon attached to their glittering masts trailed in the winds that urged them forward; yet they might perhaps have sailed under the flags of a

hundred succeeding empires, each as old as the present nationalities of the earth, during the performance of their labors. This splendid soil-forming deposit is destined to make Illinois the great centre of American wealth and population. Perhaps no other country of the same extent on the face of the globe can boast a soil so ubiquitous in its distribution and so universally productive. Enriched by all the minerals in the crust of the earth, it necessarily contains a great variety of constituents. Since plants differ so widely in the elements of which they are composed, this multiplicity of composition is the means of growing a great diversity of crops, and the amount produced is correspondingly large. So great is the fertility, that years of continued cultivation do not materially diminish the yield, and should sterility be induced by excessive working, the subsoil can be made available. This extends from 2 to 10 and even 20 and 30 feet in depth, and when mixed with the mold of the surface, gives it a greater producing capacity than it had at first. Other States have limited areas as productive, but nearly the entire surface of Illinois is arable land, and when brought under cultivation will become one continued scene of verdure and agricultural profusion. With not half of its area improved, the State has become the granary of the continent; far excels any other member of the Union in packing pork; fattens more than half of all the cattle shipped to the Eastern markets, and if prices were as remunerative, could furnish other products to a corresponding extent. Graded to a proper level, and free from obstructions, the State has become the principal theatre for the use and invention of agricultural implements. Owing to the cheapness attending the use of machinery, with a given amount of capital, a greater extent of lands can be cultivated. The severity of the labor expended is also proportionately diminished, and those engaged in husbandry have time to become acquainted with the theoretical as well as the practical part of their duties. The profound philosophy involved in the growth of plants furnishes a field for investigation and experiment requiring the highest order of talent and the most varied and extensive attainments. Agriculture, aided by chemistry, vegetable physiology and kindred branches of knowledge, will greatly enhance the productiveness of the land. Thus with the advantages of science, a superior soil, and the use of machinery, agriculture will always remain the most attractive, manly and profitable branch of industry in which the people of Illinois can engage, contributing more than any other pursuit to individual comfort, and proportionally adding to the prosperity of the State. The cultivation of the soil in all ages has furnished employment for the largest and best portion of mankind; yet the honor to which they are entitled has never been fully acknowledged. Though their occupation is the basis of national prosperity, and upon its progress more than any other branch of industry depends the march of civilization, yet its history remains to a great extent unwritten. Historians duly chronicle the feats of the warrior who ravages the earth and beggars its inhabitants, but leaves unnoticed the labors of him who causes the desolated country to bloom again, and heals with the balm of plenty the miseries of war. When true worth is duly recognized, instead of the mad ambition which subjugates nations to acquire power, the heroism which subdues the soil and feeds

the world, will be the theme of the poet's song and the orator's eloquence.

The Origin of the Prairies has been a source of speculation. One theory is that the soil resulted from the decomposition of vegetable matter under water, and that the attending conditions were incompatible with the growth of timber. According to this view, prairies are at present in process of formation along the shores of lakes and rivers. During river freshets the heaviest particles settle nearest the channel, and here by repeated deposits the banks first became elevated above the floods. These natural levies becoming sufficiently high, are overgrown with timber and inclose large areas of bottom lands back from the river, by which they are frequently inundated. The waters on these flats, when the flood subsides, are cut off from the river and form sloughs, frequently of great extent. Their shallow and stagnant waters are first invaded by mosses and other aquatic plants which grow under the surface and contain in their tissues lime, allumina, and silica, the constituents of clay. They also subsist immense numbers of small mollusks and other diminutive creatures, and the constant decomposition of both vegetables and animals forms a stratum of clay corresponding with that which underlies the finished prairies. As the marshy bottoms are by this means built up to the surface of the water, the mosses are then intermixed with coarse grasses, which become more and more abundant as the depth diminishes. These reedy plants, now rising above the surface, absorb and decompose the carbonic acid gas of the atmosphere, and convert it into woody matter, which at first forms a clayey mold and afterwards the black mold of the prairie. The same agencies, now operating in the ponds skirting the banks of rivers, originally formed all the prairies of the Mississippi Valley. We have already seen that the surface of the land was submerged during the dispersion of the drift, and in its slow emergence afterward, it was covered by vast sheets of shallow water, which first formed swamps and subsequently prairies. The present want of horizontality in some of them is due to the erosive action of water. The drainage, moving in the direction of the creeks and rivers, at length furrowed the surface with tortuous meanders, resulting finally in the present undulating prairies. The absence of trees, the most remarkable feature, is attributable first to the formation of ulmic acid, which favors the growth of herbacious plants and retards that of forests; secondly, trees absorb by their roots large quantities of air, which they cannot obtain when the surface is under water or covered by a compact sod; and thirdly, they require solid points of attachment which marshy flats are unable to furnish. When, however, the lands become dry and the sod is broken by the plow or otherwise destroyed, they produce all the varieties of arborescent vegetation common to their latitude. Indeed, since the settlement of Illinois, the woodland area of many localities extends far beyond its original limits.

The foregoing theory requires a large, unvarying quantity of water, while another, perhaps equally plausible, is based on aqueous conditions almost the reverse. It is well known that the different continental masses of the globe are in general surrounded by zones of timber, and have within them belts of grasses, and centrally large areas of inhospitable deserts. On the Atlantic side

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