the significance of time has been variously estimated by economists; and discussions of its place in economic causation have been clouded by a good deal of mystification. The notion of time has even acquired what Marx termed a fetishistic character; attempts having been made to treat it as virtually a third ultimate factor of production (along with labour and nature) and to explain the phenomenon of surplus-value in terms of its productivity. As such, the notion is a more refined cousin to the older view which regarded capital as a unique entity which had a specific productivity and value, instead of as a particular form assumed by labour in the social division of labour. That this is so does not, however, prevent it from being true that time, properly regarded, must necessarily play an important part in the framework of a number of economic problems, particularly those of accumulation and investment. Into the wider question it is not the purpose of this NOTE to enter. The intention here is simply to analyse the considerations on which the order of investment in different types of construction-projects in a socialist economy would depend. In setting this as its intention, this NOTE does not claim to enunciate any final principle (which would require a much less abstract method) but merely to define the meaning of the problem in more explicit terms.