I have completed, in the preceding chapter, all I have to say on the Standard Case. It claimed no more than to be an instrument of exploration; as such, I think it has proved its worth. Though its assumptions are so narrow, it has enabled us to get a glimpse of things which certainly look as if they should have a wider application. One is nevertheless conscious, while one is using it, of the thinness of the plank on which one is walking. We have been piling simplification upon simplification, specialization upon specialization; cannot some of them, at least, be removed?
In the present chapter and in that which follows it, I shall report on what I have been able to do in the way of extension; it is not, I fear, very much. There is no second Standard Case which seems to be analysable in comparable detail. All I can do is to test out some of the Standard Case assumptions, in order to get a general idea of the kinds of complication which arise in their absence. There are several directions in which this can be done; so what follows will divide up into rather separate enquiries.
There is one of these enquiries for which we do not need to leave the Simple Profile. In the Standard Case we did not just assume Simple Profiles; we also assumed that the Simple Profiles, of the old technique and of the new, had the same durations, the same length of construction period and the same length of utilization period. We can see what happens when this particular Standard assumption is dropped.
Most of what I can say relates to the construction period. This, it may well be felt, is the less interesting question. It would be nice to make an analysis of changes in the utilization period—that is to say, of changes in the life of the machine. Unfortunately (as we have already found in our study of the Standard Case) we can say much more about the Early Phase of a Traverse than about the Late Phase; and it is clear that changes in the life of the machine are entirely a Late Phase problem. That is why it is hard to do much about them.
Changes in the construction period are less interesting, but