The peculiar circulation of fixed capital results in a peculiar turnover. That part of the value which it loses in its bodily form by wear and tear circulates as a part of the value of the product. The product converts itself by means of its circulation from commodities into money; hence the same applies to the value-part of the instrument of labour circulated by the product, and this value drips down in the form of money from the process of circulation in proportion as this instrument of labour ceases to be a depository of value in the process of production. Its value thus acquires a double existence. One part of it remains attached to its use-form or bodily form belonging in the process of production. The other part detaches itself from that form in the shape of money. In the performance of its function that part of the value of an instrument of labour which exists in its bodily form constantly decreases, while that which is transformed into money constantly increases until the instrument is at last exhausted and its entire value, detached from its corpse, is converted into money. Here the peculiarity of the turnover of this element of productive capital becomes apparent. The transformation of its value into money keeps pace with the pupation into money of the commodity which is the carrier of its value. But its reconversion from the money-form into a use-form proceeds separately from the reconversion of the commodities into other elements of their production and is determined rather by its own period of reproduction, that is, by the time during which the instrument of labour wears out and must be replaced by another of the same kind. If a machine worth £10,000 lasts for, say, a period of ten years, then the period of turnover of the value originally advanced for it amounts to ten years. It need not be renewed and continues to function in its bodily form until this period has expired. In the meantime its value circulates piecemeal as a part of the value of the commodities whose continuous production it serves and it is thus gradually transformed into money until finally at the end of ten years it entirely assumes the form of money and is reconverted from money into a machine, in other words, has completed its turn-over. Until this time of reproduction arrives, its value is gradually accumulated, in the form of a money reserve fund to start with.