helpful to get such of
these bulletins as bear on the different sections of the book. These
will be valuable additions to your school library. The authors would
like to give a list of these bulletins bearing on each chapter, but it
would soon be out of date, for the bulletins get out of print and are
supplanted by newer ones. However, the United States Department of
Agriculture prints a monthly list of its publications, and each state
experiment station keeps a list of its bulletins. A note to the
Secretary of Agriculture, Washington, D.C., or to your own state
experiment station will promptly bring you these lists, and from them
you can select what you need for your school.

AGRICULTURE FOR BEGINNERS

CHAPTER I

THE SOIL

SECTION I. ORIGIN OF THE SOIL

The word _soil_ occurs many times in this little book. In agriculture
this word is used to describe the thin layer of surface earth that, like
some great blanket, is tucked around the wrinkled and age-beaten form of
our globe. The harder and colder earth under this surface layer is
called the _subsoil_. It should be noted, however, that in waterless and
sun-dried regions there seems little difference between the soil and the
subsoil.

Plants, insects, birds, beasts, men,--all alike are fed on what grows in
this thin layer of soil. If some wild flood in sudden wrath could sweep
into the ocean this earth-wrapping soil, food would soon become as
scarce as it was in Samaria when mothers ate their sons. The face of the
earth as we now see it, daintily robed in grass, or uplifting waving
acres of corn, or even naked, water-scarred, and disfigured by man's
neglect, is very different from what it was in its earliest days. How
was it then? How was the soil formed?

Learned men think that at first the surface of the earth was solid rock.
How was this rock changed into workable soil? Occasionally a curious boy
picks up a rotten stone, squeezes it, and finds his hands filled with
dirt, or soil. Now, just as the boy crumbled with his fingers this
single stone, the great forces of nature with boundless patience
crumbled, or, as it is called, disintegrated, the early rock mass. The
simple but giant-strong agents that beat the rocks into powder with a
clublike force a millionfold more powerful than the club force of
Hercules were chiefly (1) heat and cold; (2) water, frost, and ice; (3)
a very low form of vegetable life; and (4) tiny animals--if such minute
bodies can