In quite a different context Marx appears to endorse the opinion expressed above. In _Theories on the Surplus Value_, vol ii, part 2, analysing the conversion of revenue into capital, he speaks of the peculiar reproduction of the fixed capital, the replacement of which in itself already provides a fund for accumulation. He draws the following conclusion: 'The point we have in mind is as follows: even if the aggregate capital employed in machine manufacture were just large enough to make good the annual wear and tear of the machines, many more machines could be annually produced than are required, since the wear and tear is in parts merely _idealiter_ and must be made good _realiter_, _in natura_, only after a certain number of years. Capital so employed supplies each year a mass of machinery which becomes available for, and anticipates new, capital investments. Let us suppose, for instance, a machine manufacturer who starts production this year. During this year, he supplies machines for £12,000. If he were merely to reproduce the machines he has manufactured, he would have to produce, during the subsequent eleven years, machines for £1,000 only, and even then, a year's production would not be consumed within the year. Still less could it be consumed, if he were to employ the whole of his capital. To keep this capital working, to keep it reproducing itself every year, a new and continuous expansion of the branches of manufacture that require these machines, is indispensable. This applies even more, if the machine manufacturer himself accumulates. In consequence, even _if the capital invested in one particular branch of production is simply being reproduced_,[88] a continuous accumulation in the other branches of production must go with it.'[89] We might take the machine manufacturer of Marx's example as illustrating the production of fixed capital. Then the inference is that if society maintains simple reproduction in this sphere, employing each year a similar amount of labour for the production of fixed capital (a procedure which is, of course, impossible in practical life), then annual production in all other spheres must expand. But if here, too, simple reproduction is to be maintained, then, if the fixed capital once created is to be merely renewed, only a small part of the labour employed in its creation can be expended. Or, to put it the other way round: if society is to provide for investment in fixed capital on a large scale, it must, even assuming simple reproduction to prevail on the whole, resort periodically to enlarged reproduction.