People once gave no thought to the purity of the water that they drank. When there were few people, water did not easily become impure. One could drink water wherever one found it and there was small risk of harm. Now in many places there are so many thousands of people gathered together that they have to take the greatest care about drinking water, in order to keep in good health. To get pure water it is often necessary to bring it many miles from mountainous regions where no one lives.
Clothing is another thing that concerns us very much. Our ancestors were not troubled about their clothing. In the warm countries they went almost naked. Where it was cold the skins of animals served very well. Changes of fashion did not disturb them and cause them to throw away warm covering. To supply ourselves now with clothing we call upon Nature for many things. As she cannot, without our help, furnish what we need, we have to keep a great number of flocks, for their wool and skins, and cultivate vast fields of cotton and flax.
When Nature raised in her own way the berries, grains, and roots that the first men ate, no thought was given to the soil in which these things grew. In truth, it was not necessary to pay any attention to the soil. Nature is very careful in her way and never makes the soil poor by growing more plants than it can support. In her own gardens she always renews the foods in the soil which the plants require as fast as they take them away.
The needs of men have increased so fast that the soil has often been forced to grow more than it ought. Men have been a long time in learning that they cannot keep on growing the same crops on the same soil year after year without supplying to the soil extra foods, or fertilizers, as we call them. The care of the soil is another thing to which we have to give attention, but which did not worry our ancestors.
Nature clothes the earth with a carpet of grasses, bushes, or trees. When the rain falls on the ground, their roots hold the soil so firmly that it usually washes away only very slowly. When men first began to cultivate the soil, they paid no attention to the fact that water washes away the loose earth very easily. In this loose earth at the top of the ground is stored most of the food which the plants require. Care of the surface of the ground is, then, another thing which we have to keep in mind.
Men at first made shelters for themselves from anything that was at hand, such as bark, skins, rock, or earth. When they learned to make sharp-edged tools, they began to use trees. Where it is cold, much wood is required to build warm houses. As the numbers of men increased, they used greater and greater quantities of wood. Wood also proved to be most useful for many other purposes than house building. In order to plant larger fields the trees were cut down or burned off, without thought of doing any harm. In time trees became scarce in many parts of the world and men began to realize that care must be used or the supply of wood might fail them.
Coal was finally discovered and men said, "Now we have something that will last always, for there must be an inexhaustible amount in the earth beneath our feet. All that we shall have to do is to dig it out." When men grew wiser they learned that coal must not be used carelessly any more than the other gifts of Nature; otherwise the supply may give out and leave them with nothing to take its place.
George J. Young