However, it is in the nature of things that the circuit itself
 necessitates the fixation of capital for certain lengths of time in its
 various phases. In each of its phases industrial capital is tied up with
 a definite form: money-capital, productive capital, commodity-capital.
 It does not acquire the form in which it may enter a new transformation
 phase until it has performed the function corresponding to each particular
 form. To make this plain, we have assumed in our illustration that the
 capital-value of the quantity of commodities created at the stage of production
 is equal to the total sum of the value originally advanced in the form
 of money; or, in other words, that the entire capital-value advanced in
 the form of money passes on in bulk from one stage to the next. But we have
 seen (Buch I, Kap. VI) [English edition: Ch. VIII. — Ed.] that
 a part of constant capital, the labour instruments proper (e.g., machinery),
 continually serve anew, with more or less numerous repetitions of the same
 process of production, hence transfer their values piecemeal to the products.
 It will be seen later to what extent this circumstance modifies the circular
 movement of capital. For the present the following suffices: In our illustration
 the value of productive capital amounting to £422 contained only
 the average wear and tear of factory buildings, machinery, etc., that is
 to say only that part of value which they transferred to the yarn in the
 transformation of 10,600 lbs. of cotton into 10,000 lbs. of yarn, which
 represented the product of one week’s spinning of 60 hours. In the means
 of production, into which the advanced constant capital of £372 was
 transformed, the instruments of labour, buildings, machinery, etc., figured
 as if they had only been rented in the market at a weekly rate. But this
 does not change the gist of the matter in any way. We have but to multiply
 the quantity of yarn produced in one week, i.e., 10,000 lbs. of yarn, by
 the number of weeks contained in a certain number of years, in order to
 transfer to the yarn the entire value of the instruments of labour bought
 and consumed during this period. It is then plain that the advanced money-capital
 must first be transformed into these instruments, hence must have gone
 through the first phase M — C before it can function as productive capital
 P. And it is likewise plain in our illustration that the capital value
 of £422, embodied in the yarn during the process of production, cannot
 be part of the value of the 10,000 lbs. of yarn and enter the circulation
 phase C' — M' until it is ready. It cannot be sold until it has been spun.