(d) Harm done by drying, chilling or malarious winds;
(e) The shifting of wind-driven sands which, when not held in place by forests, often cover and ruin fertile land, and even bury fences and buildings;
(f) The undue multiplication of insects harmful to vegetation.
III. As beautifying a region and affording healthful retreats for tired and sick people.
But forestry treats not only of this use and value in the woods, but also tells us:
B. How to make them of use: that is, how to manage forest property so as to make it yield the greatest benefit in the long run, to the individual owner, to the community, and to future generations. This involves the study of a great many questions which we may classify as follows:
I. On what kinds of soil and in what situations shall we keep or plant trees?
II. What kinds of trees shall we raise in any particular place?
III. At what age, and in what way shall we cut the trees of each kind in a given region?
IV. What are the methods of marketing forest products which will secure the greatest profit?