the way we have been trampling on something very important which we
will notice on our way back. In this field we find a coarse sandy
soil, in the next one a soil that is finer and stiffer. The plow is
turning up a reddish soil. In the garden we find the soil quite dark
in color.

But these are only a few of the things we have found. If you have used
your notebook you will discover that you have long lists of objects
which you have noticed, and these may be grouped under the following
headings: Animals, Plants, Soils, Buildings, Tools, etc.

The farmer, then, in his work on the farm deals with certain agents,
chief among which are Soils, Plants, Animals, Tools and Buildings.
Other agents which assist or retard his work according to
circumstances are the air, sunlight, heat, moisture, plant food,
microscopic organisms called bacteria, etc. These agents are
controlled in their relations to one another by certain forces which
work according to certain laws and principles of nature. To work
intelligently and to obtain the best results the farmer must become
familiar with these agents and must work in harmony with the laws and
principles which control them.

Let us take up the study of some of these groups of agents, beginning
with the most important or central one on the farm.

Which do you think is the most important group? Some will say "tools."
The majority will probably say, study the soil first, "because we must
work the soil before we can grow good crops." Some few will mention
"plants." This last is right. The farm animals are dependent on plants
for food. We till or work the soil to produce plants. Plants are