It first existed in the form of yarn, while now it exists in the form of money. Thus a substantial distinction is evident between the first stage M---C and the last stage C---M. There the advanced money functions as money-capital, because it is transformed by means of the circulation into commodities of a specific use-value. Here the commodities can serve as capital only to the extent that they bring this character with them in ready shape from the process of production before their circulation begins. During the spinning process, the spinners create yarn value to the amount of £128. Of this sum, say £50 represent to the capitalist merely an equivalent for his outlay for labour-power, while £78 -- when the degree of exploitation of labour-power is 156 per cent -- form surplus-value. The value of the 10,000 lbs. of yarn therefore embodies first the value of the consumed productive capital P, the constant part of which amounts to £372 and the variable to £50, their sum being £422, equal to 8,440 lbs. of yarn. Now the value of the productive capital P is equal to C, the value of its constituent elements, which in the stage M---C confronted the capitalist as commodities in the hands of their sellers.
In the second place, however, the value of the yarn contains a surplus-value of £78, equal to 1,560 lbs. of yarn. C as an expression of the value of the 10,000 lbs. of yarn is therefore equal to C plus DC, or C plus an increment of C (equal to £78), which we shall call c, since it exists in the same commodity-form as now the original value C.
The value of the 10,000 lbs. of yarn, equal to £500, is therefore represented by C + c = C'. What turns C, the expression of the value of 10,000 lbs. of yarn, into C' is not the absolute magnitude of its value (£500), for that is determined, as in the case of any other C standing for the expression of the value of some other sum of commodities, by the quantity of labour embodied in it. It is its relative value-magnitude, its value-magnitude as compared with that of capital P consumed in its production. This value is contained in it plus the surplus-value supplied by the productive capital. Its value is greater, exceeds that of the capital-value by this surplus-value c. The 10,000 lbs. of yarn are the bearers of the capital-value expanded, enriched by this surplus-value, and they are so by virtue of being the product of the capitalist process of production.
C' expresses a value-relation, the relation of the value of the commodities produced to that of the capital spent on their production, in other words, expresses the fact that its value is composed of capital-value and surplus-value.
The 10,000 lbs. of yarn represent commodity capital, C', only because they are a converted form of the productive capital P, hence in a connection which exists originally only in the circuit of this individual capital, or only for the capitalist who produced the yarn with the help of his capital.
It is, so to say, only an internal, not an external relation that turns that turns the 10,000 lbs. of yarn in their capacity of vehicles of value into a commodity-capital. They exhibit their capitalist birthmark not in the absolute magnitude of their value but in its relative magnitude, in the magnitude of their value as compared with that possessed by the productive capital embodied in them before it was transformed into commodities. If, then, these 10,000 lbs. of yarn are sold at their value of £500, this act of circulation, considered by itself, is identical with C---M, a mere transformation of an unchanging value from the form of a commodity into that of money. But as a special stage in the circuit of an individual capital, the same act is a realisation of the capital-value embodied in the commodity to the amount of £422 plus the surplus-value, likewise embodied in it, of £78. That is to say it represents C'---M', the transformation of the commodity-capital from its commodity-form into the money form. [4]
The function of C' is now that of all commodities, viz.: to transform itself into money, to be sold, to go through the circulation stage C---M.
So long as the capital, now expanded, remains in the form of commodity-capital, lies immovable in the market, the process of production is at rest. The commodity-capital acts neither as a creator of products nor as a creator of value. A given capital-value will serve, in widely different degrees, as a creator of products and value, and the scale of reproduction will be extended or reduced commensurate with the particular speed with which that capital throws off its commodity-form and assumes that of money, or with the rapidity of the sale. It was shown in Book I that the degree of efficiency of any given capital is conditional on the potentialities of the productive process, which to a certain extent are independent of the magnitude of its own value. [English edition: Karl Marx, Capital , Vol. I, pp. 602-08. -- Ed. ] Here it appears that the process of circulation sets in motion new forces independent of the capital's magnitude of value and determining its degree of efficiency, its expansion and contraction.