It does not mean that we shall cease to cut our timber, but it does mean that we shall not waste two-thirds of all that is cut, as we are doing at present. It means, too, that we shall take better care of articles manufactured from it, and most of all, it means that, when a tree is cut down another shall, whenever possible, be planted in its stead to provide for the needs of the future. It means that we shall not allow the farms of our country to lose five hundred million dollars in value every year by letting the rich top-soil drain off into our rivers, because we have cut away the trees whose roots held the soil in place. It also means that we shall not steadily rob the land of the elements that would produce good crops, and put nothing back into the soil. It means that we shall not kill the birds that destroy harmful insects and thus invite the insects to destroy the crops that we have cultivated with such care. It does not mean that we shall let our mines of coal and iron lie unused, as the miser does his gold, but that we shall, while taking what we need, leave as little waste in the mine as possible, and shall use what we take in the most economical way. This means a saving of money to the user, as well as a conservation of resources. It means, too, that we shall not allow our water-power to remain unused, while we burn millions of tons of coal in doing the work that water-power would do better. It means that we shall not allow enough natural gas to escape into the air every day to light all the large cities in the United States. It means that we shall take better care of the life and health of the people. This is the true conservation. In the following chapters we shall take up each of the great resources in turn, shall see what we have used, what we have wasted, what remains to us, how long it will continue at the present rate, how it may be used more wisely, and how it may be replaced, if that be possible, or what may be used instead of those which can not be renewed. We shall study how we may make the most of all that nature has given us and develop our country to the highest possible point, how we may rise far above our present level in comfort, convenience, and abundance, and yet do all these things with much less waste than we now permit. CHAPTER II THE SOIL The soil is the greatest of our natural resources. We may almost say that it is greater than all the others combined, for from it comes all of our food; a large part of it directly as plants which grow in the soil and which we eat in the form of roots, leaves, grains, berries, fruits, and nuts; and a part of it indirectly as animals, which have received their food supply from the plants.