There are, of course, other conditions that modify these differences, but the soil is one of the greatest natural resources of any people and largely determines its manner of life. It is greater than the mines of all the metals and fuel, the quarries of stone, the forests of timber, and the streams. with their latent power and stock of food animals.

The soil, like almost every other natural resource, may be expended and wasted, and its usefulness, if not destroyed, may be brought to an exceedingly ineffective condition by careless and ignorant use.

FIG. 2.-Accumulations of snow and ice in mountainous regions or regions of high latitude slide down the slope as shown in the above picture of an Alaskan glacier. This has been a very important means of soil formation, having at one time covered all of New

York

On the other hand, so susceptible of re-creation is the soil that under careful and wise handling it is able to maintain its productiveness with scarcely a trace of diminution for decade after decade and century after century. Such has been the history of the soils of many sections of Europe and of the other parts of the world. This long-continued productivity has not always been attained as a result of thorough scientific knowledge, but has rather been the outgrowth of empirical practice by which permanently efficient customs in tillage have been developed.

Nevertheless, probably every one will agree that a more permanently effective system of husbandry may be developed as a result of accurate

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and thorough knowledge of all the processes and operations involved in producing crops from the soil than is possible by the older " rule of thumb " method. So broad are the relationships of good soil management that no person may properly claim the right to be exempt from a certain fundamental knowledge of the soil and its conservation, however far he may be removed professionally.

THE NATURE OF THE SOIL

The soil material the superficial area of the earth is so thin as to be infinitesimal in thickness when compared with the diameter of the earth. We commonly define the soil as the surface area of the earth's crust that

FIG. 3. The water from the melting of ice at the front of a glacier carries away and sorts the rock materials and deposits them along its course, later to serve as soil. Much of the land along the lakes and through the valleys in New York has been formed in this way

is capable of supporting plant growth. The growth that it will support may be ever so simple, as in the case of a few bacteria on some rock cliff, or it may be a tall field of corn on a rich river plain, or a dense forest of trees on a fertile plateau.

We include in the soil all the material to the depth to which plant roots are able to distribute themselves. It therefore includes a wide range of material in depth and character. It may be deep or shallow, coarse or fine, loose or compact, light or dark, wet or dry. It is all soil because it is a medium for the growth of some kind of plant. In general, the soil may be divided into two classes of material: (a) the particles of mineral and fragments of rock, and (b) bits of organic matter of both plant and animal origin that have become more or less decomposed.

results in different kinds of plant growth. Thus, wheat is grown on deep, fertile loam, and mosses and ferns on thin, rocky slopes; truck crops are grown on dry, warm sand, and sphagnum or sweet flag on mucky marshes. The great variety in plants is due to the great variety of soil conditions that nature affords. Man's province as a tiller of the soil and grower of plants is to change the conditions of the soil so that they shall be more favorable to the crops he desires to grow.

The soil is a complex body and is the result of a complex set of processes, yet we may learn many things about its nature and operation. The fragments of minerals and rocks of which it is chiefly composed have been derived through the operation of many agencies that work together to break down and transport the rocks from which the soils are formed.

Soil is sometimes called pulverized rock, but it is more. Together with the organic matter of which it is composed, it is the seat of activity of millions of bacteria and of minute

Switzerland, the tops are capped by snow and ice which slide down the gorges with a tremendous grinding force; the ice melts and this great

volume of water flows away with such violence as to furrow the rock slopes and carry away every bit of loose material. Trees and smaller plants pry their roots into the fissures, and winds send blasts of sand and dust against the ledges. Thus by degrees the mountain of rock becomes a plain of soil.

One may see these results wherever he is, and may observe the processes that have given rise to them. They may differ in magnitude but not in kind. Note how frost breaks up clods of clay and even of stone; how the rivulets after a rain gully the hillside and leave a mass of gravel or mud where the water comes to rest. Then note the plants that spring up, and observe their roots-how they thread their way about through the spaces in rock and soil, expanding each a little by their growth and search for water and food.

FIG. 6.- Micro-photograph of silt soil showing the much smaller size of particles. The particles are of the same general shape and variety in mineral composition as the sand Owing to its greater fineness, the food contained in silt is much more available

KINDS OF SOIL

As a result of the many processes at work, we find two general classes of soil. One results from the gradual disintegration and decay of rocks. Such soils have been formed in place; that is, they have not been moved, and we call them sedentary. The famous limestone soil of Kentucky is of this class. The other class has been moved more or less, and is called transported soil. Water, wind, and ice have been the chief means of transporting the soil material. Our best soils, as a rule, have been formed in the latter way. In New York the greater part of the soil on the uplands

FIG. 7.-The accumulation of sediment and the remains of swamp plants in wet places form extensive areas of very fertile soil, often of a muck character

has been formed by ice, which has ground up the rock from many sources and mixed it together in the helter-skelter stony mass generally found. Along the rivers and streams, on the plains of Lakes Erie and Ontario, and on the Long Island coast, the soils owe their character to water which has transported, sorted, and deposited the material in groups, or areas, of considerable uniformity. Thus we find clay in one place, silt in another, and various grades of sand, gravel, and stones in still other places. These different characters give the soils different relations to crop growth. Soils formed by water are, in general, the most extensive and important agriculturally. They are usually fine and uniform in texture and level in topography.