I do not mean to say that there are not other proximate causes. The growing complexity and interdependence of the machinery of production, which makes each shock or stoppage propagate itself through a widening circle; the essential defect of currencies which contract when most needed, and the tremendous alternations in volume that occur in the simpler forms of commercial credit, which, to a much greater extent than currency in any form, constitute the medium or flux of exchanges; the protective tariffs which present artificial barriers to the interplay of productive forces, and other similar causes, undoubtedly bear important part in producing and continuing what are called hard times. But, both from the consideration of principles and the observation of phenomena, it is clear that the great initiatory cause is to be looked for in the speculative advance of land values. In the preceding chapter I have shown that the speculative advance in land values tends to press the margin of cultivation, or production, beyond its normal limit, thus compelling labor and capital to accept of a smaller return, or (and this is the only way they can resist the tendency) to cease production. Now, it is not only natural that labor and capital should resist the crowding down of wages and interest by the speculative advance of rent, but they are driven to this in self-defense, inasmuch as there is a minimum of return below which labor cannot exist nor capital be maintained. Hence, from the fact of speculation in land, we may infer all the phenomena which mark these recurring seasons of industrial depression. Given a progressive community, in which population is increasing and one improvement succeeds another, and land must constantly increase in value. This steady increase naturally leads to speculation in which future increase is anticipated, and land values are carried beyond the point at which, under the existing conditions of production, their accustomed returns would be left to labor and capital. Production, therefore, begins to stop. Not that there is necessarily, or even probably, an absolute diminution in production; but that there is what in a progressive community would be equivalent to an absolute diminution of production in a stationary community—a failure in production to increase proportionately, owing to the failure of new increments of labor and capital to find employment at the accustomed rates. This stoppage of production at some points must necessarily show itself at other points of the industrial network, in a cessation of demand, which would again check production there, and thus the paralysis would communicate itself through all the interlacings of industry and commerce, producing everywhere a partial disjointing of production and exchange, and resulting in the phenomena that seem to show overproduction or overconsumption, according to the standpoint from which they are viewed.