of the northern Valley flooded much or all of it, and the distribution of the drift was effected. There were rushing currents that carried everything movable before them. The pebbles and heavier material naturally found the lowest place at the bottom of the drift. As the force of the currents diminished, the lighter and finer material was spread over the mass of loose stone, sometimes in very deep embankments of mud, and in the broad lakes and still waters of the period the silt containing the largest amount of material required for a rich, deep soil was slowly deposited.

This continued for some time after the rise had again commenced. When this rise had drained off most of the region the wearing down of the present river channels began. The vast amount of water to be drained off made very large streams, which may now be estimated in the distances from bluff to bluff on each side of the river bottoms, for originally the Valleys did not exist, the whole surface being very nearly, or quite, even and all the deep cuts of the valleys (probably where still more ancient river beds had been) were worn out by the streams. Sometimes the gradual rise of the general surface, which caused this powerful wearing down of the channels, was stopped for a while and the shore line formed a terrace or bench. This is called the Terrace epoch.

The Champlain Era, during which the drift was chiefly distributed, was so called because its effects are very marked in the region of that lake, and it was first carefully studied there. The Glacial, Champlain and Terrace Eras were parts of the one great and important period which gave the Valley its preeminence as an agricultural region. The first provided the material for a deep undersoil, the second spread it out systematically, so that the whole region should get the benefit of it, laid the coarse material beneath so as to form a natural drain, and held the lighter and richer materials in solution in the waters until they could be laid on the top.

The level prairies were the sites of shallow lakes which

ORIGIN OF PRAIRIE SUBSOILS.

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finally became marshes in most cases; the rolling prairies testify to the rush and recoil of the shallow fresh-water seas that followed the melting of the ice; and the ravines, the hills, and the smaller valleys indicate the washing away of portions of the surface in the process of draining. The plains, that gradually rise from the Missouri River, and from about the western boundary of the State of Missouri until, at the foot of the mountains, nearly 600 miles distant, they are 5,000 feet above the level of the sea, washed very heavily and sent much of the material at the surface to be distributed in the central Valley, or to fill up the basin of the lower Mississippi. This material along the rivers is a purer and heavier deposit than is generally found elsewhere. Old river beds existed here before the age of ice, and the finest and best material naturally flowed toward these lowest levels. When the level of the land was so near that of the water as to render the currents light, very thick deposits were made. Sometimes the current would be stopped by an obstruction in the channel and then a wide-spreading lake would be formed, and so heavily were the waters laden with earthy matter that in time the whole lake would, perhaps, be filled with it. Nearly a third part of Iowa-the western part-the eastern part of Nebraska, with some portions of Kansas and Missouri, were covered by such a vast lake filled with this "Bluff Formation " or "Loëss," as it is called, and vast quantities of it were used to fill up the lower Valley of the Mississippi River. It is still being deposited at its various mouths, and making land

into the Gulf.

These surface deposits contain much loam and chemical material required in vegetable growth, and to it are due the remarkable and durable qualities of the immediate undersoil. As soon as the water was drawn off or became sufficiently shallow, a rich vegetation sprung up and the marshes were filled, in the course of time, with a vegetable mold of great depth, and it accumulated over all the surface of the higher

ground, though it was frequently washed down from the knolls and hills to lower surfaces. Unnumbered years of this growth and decay of plants and grasses on the prairies and fall of leaves in the forests collected a vast reserve of decayed organic remains, or vegetable mold, which put it in the best possible condition for the husbandman. Nature took abundance of time to fertilize the Valley and the civilized farmer found it the richest garden. The Animal Kingdom lent its aid to the Vegetable in this furnishing process. The vast mastodon, herds of buffalo and deer, and countless other animals, large and small, fed on its herbage and were "herded" there from birth to death. Thus was the work of preparing this favored region for its human occupant completed.

CHAPTER IV.

VEGETABLE AND ANIMAL LIFE

ITS ORIGIN AND PROGRESS.

The mysterious force we call Life is a wonderful and most intelligent Architect. All the resources of chemistry are at its command, and the best trained skill of science fails. to reproduce its results, even with the same materials used in the same proportions. The usual laws and qualities of the matter it employs as building material bow to it as their master, being suspended in its presence, or adapting their action to its purposes; and, armed with such authority, this invisible intelligence raises matter to a higher level of powers and uses with an unerring certainty and cunning skill wonderful to behold. In its hands dead matter becomes alive. It shows inexhaustible ingenuity in varying the form and details of different structures. Now it works them out with exquisite finish of detail, but so minute that many thousands may dwell together in a single drop of water with roomy ease, and again builds the ponderous elephant or whale, the tiny plant, the coarse shrub, or the mighty tree. The powers conferred on these works of its hand are equally various and wonderful. This plant produces a virulent poison, that a delicate perfume, the other a nourishing fruit. There is an endless display of different forms, qualities, and uses, which it is the office of the science of Botany among plants, and of Zoology among animals, to investigate, and the fields are so large that, after hundreds of years of study by enthusiastic learners, they are explored only in part.

The animal world is higher in the scale, more varied in

form, in qualities, and in uses, to which its instincts and dispositions exactly correspond. Fierceness and courage go with powerful weapons of attack, while to weakness and timidity are joined strong defences, swiftness in flight or cunning arts of evasion. Each living thing exists for some sufficient reason or purpose, and every individual form of life is the intelligent development of a thought which it would require a volume to present in full detail.

This skillful and magic builder has been unwearied in labor. Ever since the seas were cooled and the surface rock pulverized, so as to furnish the necessary material for its operations, the products of its activity have been innumerable, with a constant variation of species of the same order or addition of different classes. Twenty thousand species from the Palæozoic rocks have been described, and these are probably but a small part of the number then existing; and so numerous were the individuals that the defensive armor or stony framework of some classes of them has, after their death, been formed into rocks of vast extent and hundreds of feet in thickness.

But various as are the forms which the life force produces its mode of operating is at first uniform. Its building process is commenced with a cell of soft or plastic matter which seems to understand perfectly what it is to produce, what materials are required, and how they are to be handled. A call is issued for material which passes through the wall of the cell and presents itself with obedient readiness. It is dissolved, re-combined, and laid in place. The cell expands, is divided, and the same process continued in each cell until the proper dimensions have been reached in every direction, and the necessary form and consistence has been given to every part of the organism; different materials or different combinations of the same material often being employed in different parts. Each part is endowed with the capacity to perform its appropriate work in the general result to be accomplished by the complete living thing in which it is placed. A multitude