The same thing may be seen in every rapidly growing city. If the land of superior quality as to location were always fully used before land of inferior quality were resorted to, no vacant lots would be left as a city extended, nor would we find miserable shanties in the midst of costly buildings. These lots, some of them extremely valuable, are withheld from use, or from the full use to which they might be put, because their owners, not being able or not wishing to improve them, prefer, in expectation of the advance of land values, to hold them for a higher rate than could now be obtained from those willing to improve them. And, in consequence of this land being withheld from use, or from the full use of which it is capable, the margin of the city is pushed away so much farther from the center. But when we reach the limits of the growing city—the actual margin of building, which corresponds to the margin of cultivation in agriculture—we shall not find the land purchasable at its value for agricultural purposes, as it would be were rent determined simply by present requirements; but we shall find that for a long distance beyond the city land bears a speculative value, based upon the belief that it will be required in the future for urban purposes, and that to reach the point at which land can be purchased at a price not based upon urban rent, we must go very far beyond the actual margin of urban use. Or, to take another case of a different kind, instances similar to which may doubtless be found in every locality. There is in Marin County, within easy access of San Francisco, a fine belt of redwood timber. Naturally, this would be first used, before resorting for the supply of the San Francisco market to timber lands at a much greater distance. But it yet remains uncut, and lumber procured many miles beyond is daily hauled past it on the railroad, because its owner prefers to hold for the greater price it will bring in the future. Thus, by the withholding from use of this body of timber, the margin of production of redwood is forced so much farther up and down the Coast Range. That mineral land, when reduced to private ownership, is frequently withheld from use while poorer deposits are worked, is well known, and in new States it is common to find individuals who are called “land poor”—that is, who remain poor, sometimes almost to deprivation, because they insist on holding land, which they themselves cannot use, at prices at which no one else can profitably use it.