IN considering the value of any great land for the uses of civilized man it is of first importance to take into account the character of its soil coating and the relation of that layer of earth material to agriculture. Whatever be the other advantages of a country-however rich its mineral resources, good its climate, and advantageous its situation with reference to the trade of the world -- its fitness for the occupation of cultivated people is in the main determined by the harvests which it may yield. Therefore, at the outset of our inquiry into the several great divisions of the earth resources which are provided by North America, we shall note the tillage value of its fields. In order to acquire a clear conception of the problems presented by the soil, it is well to begin the inquiry with some general considerations as to the way in which this coating is formed, how its fertility is maintained, increased, or impaired, and how it stands related to the life which may grow upon it.
The phenomena exhibited by the soil coating of the earth are so familiar that they are often contemptuously overlooked. The mass of decaying mineral and organic matter of which the layer is composed appears to most persons mere dirt. They fail to conceive the marvelous chemical and vital processes which are there in action, or how intimately the work which they do is related to the life of land and sea. It is extremely desirable to have these crude notions cleared away, and to have them replaced with correct ideas which will serve to ennoble our understanding of this, the most marvelous of all the parts of our earth. This end can only be obtained through knowledge. Every person should gain at least a general notion as to the history and function of the soil coating, in order that he may become a guardian of the fields on which the life of his kind intimately depends.
Taking a bit of ordinary soil from the layer in which the plant roots feed, the observer may even with the naked eye, but better with a hand lens, perceive that the mass is made up of