_Why the Perishability of Capital Goods does not put Capital out of Existence._--Perishability is the most striking trait of capital goods. Each particular one comes and goes, but there is always a stock of them on hand; for when one is on the point of going, another is ready to take its place and keep up the succession. New tools replace old tools; new materials replace those that are finished and withdrawn, and so it comes about that a stock of such things abides forever. Not one of the individual instruments is permanent, for each one only does its part in keeping up an endless procession. It is the procession that is always there--a moving series of individual goods, not one of which has more than a transient economic career. Each one helps to keep up the supply of permanent capital just as each man, taking his turn in an endless succession of laborers, serves during his brief life to keep up the permanent force of laboring humanity. Men come and go, but "labor"--a mass of working humanity--abides; and so capital goods come and go, but a stock of them abides, kept up by perpetual replacement. We may trace the career of any single instrument from a beginning to an end; but we may, on the other hand, cease to look at any instruments that we single out and identify and look rather at the procession of them; and if we do this, we look at a body which never wastes away, though the things that compose it are, separately considered, forever wasting. There are many kinds of transient things which, by the same process of renewal, constitute permanent entities. Composing a human body at this moment are certain tissues that can be separately identified; and if we watch any one of them, we shall see it going in a short time to destruction. Yet the body lasts while life continues. Indeed, the evidence of the life itself is the discarding and replacing of the tissues. A living body is a durable thing, though the particular tissues that at any one time compose it are not so. In a like way drops of water make a river, and this is a permanent thing, however rapidly its composition changes. The waterfall that drives the machinery of a mill is permanent, though no particular particle of water remains in it for more than a moment. Society is permanent, though the men who compose it are short-lived. In an exactly similar way a body of capital goods is maintained as a perpetual instrumentality of production. _This is capital properly so called._ It is, as it were, a quasi-living body, perpetuated by the constant replacement of the component parts, which are destroyed as its normal activities go on.