We have now to recognize, first, that production is indirect and time-consuming. It is indirect in that the original factors of production-labour and land-yield final consumable output only after transformation into a variety of intermediate products. And production is time-consuming in that the flow of output in any particular period is the consequence of a process of transformation that reaches back into the past. It is necessary, secondly, to take account of the fact that the level of a society's scientific and technical attainment, and therefore the production processes open to it, changes with time and can be raised by measures specifically directed to this end. In the early part of this chapter I shall examine some of the more important consequences of the fact that production takes time; having done this, I shall refer to some of the further complications introduced by changing technology.