It is thought that in the early stages of the earth's career only the lower forms of vegetable life could find a footing on its surface.

The various Alga?, Lichens, Mosses, were able to pick up a living at first.

In due course they died, and their remains mingled with the surface soil, thus gradually bringing about a compost suitable for the growth of higher plants "Dissolve to dust and make a way For bolder foliage nursed by their decay".

And so on, from one stage to another, one class of plants succeeding another, and some even being crushed out of existence altogether, as we learn from the fossil remains found in coal seams, shale, etc.

Animals, when they came, helped also to make our soils, and, like the primitive plants, many of these died out under the stress of competition from newer races. Worms also play an important part in the ventilation of the soil, and wherever very large numbers are present it may be taken as a sign that the subsoil is in a wet and heavy condition, and should be trenched or at least double dug.

These natural soil-forming agencies, although of the greatest importance, are nevertheless too slow for horticultural and agricultural purposes. If a farmer or a gardener waited until the rain, frost, snow, heat, cold, and wind, etc, converted a heavy clay soil into a fertile condition, he and his race would soon become extinct. He therefore hastens the process of disintegrating various rocks and soils by such cultural operations as ploughing, digging, trenching, manuring, etc. He "tills" the ground, and by ever exposing fresh surfaces to the natural agencies of the weather, he, more or less quickly, brings the soil into a condition capable of bearing large crops of cereals, fruits, flowers, and vegetables. This condition is known as fertile, whereas a soil that will not respond to such operations is known as sterile.