A supply in the form of productive capital exists in the shape
 of means of production, which already are in the process of production
 or at least in the hands of the producer, hence latently already in the
 process of production. It was seen previously that with the development
 of the productivity of labour and therefore also with the development of
 the capitalist mode of production — there is a steady increase in the
 mass of means of production (buildings, machinery, etc.) which are embodied
 once and for all in the process in the form of instruments of labour, and
 perform with steady repetition their function in it for a longer or shorter
 time. It was also observed that this increase is at the same time the premise
 and consequence of the development of the social productive power of labour.
 The growth, not only absolute but relative, of wealth in this form (cf.
 Buch I, Kap XXIII, 2) [English edition: Ch. XXV, 2. — Ed.] is characteristic above all of the capitalist mode of production. The material forms of existence of constant capital, the means of production, do not however consist only
 of such instruments of labour but also of materials of labour in various
 stages of processing, and of auxiliary materials. With the enlargement
 of the scale of production and the increase in the productive power of
 labour through co-operation, division of labour, machinery, etc., grows
 the quantity of raw materials, auxiliary materials, etc., entering into
 the daily process of reproduction. These elements must be ready at hand
 in the place of production. The volume of this supply existing in the form
 of productive capital increases therefore absolutely, in order that the
 process may keep going — apart from the fact whether this supply can be
 renewed daily or only at fixed intervals — there must always be a greater
 accumulation of ready raw material, etc., at the place of production than
 is used up, say, daily or weekly. The continuity of the process requires
 that the presence of its conditions should not be jeopardised by possible
 interruptions when making purchases daily, nor depend on whether the product
 is sold daily or weekly, and hence is reconvertible into its elements of
 production only irregularly. But it is evident that productive capital
 may be latent or form a supply in quite different proportions. There is
 for instance a great difference whether the spinning-mill owner must have
 on hand a supply of cotton or coal for three months or for one. Patently
 this supply, while increasing absolutely, may decrease relatively.