Summary

The purpose of this chapter is to consolidate. No new ideas are introduced; instead we try to sort the main thread from the side issues, and the parts that are reasonably clear and firm from the parts that are still fuzzy. The core of the chapter is a set of seventeen statements, seventeen vertebrae that form the backbone of the book, but there are also a preface and a postscript. The preface provides the setting for the seventeen-part core and the postscript takes up the question of where to go next. The purpose of the book was given at the start of Chapter 1. Even at that early point, a stressed cylinder was used as an example. The purpose is to make headway with the question: if a state of chemical equilibrium exists under hydrostatic stress and is disturbed by making the stress nonhydrostatic, what processes begin to run, and what quantitative relations should we expect to be followed? Before the seventeen-part "answer" it is to be noted that there are two alternative ways of dividing the subject matter into two parts. The division scheme is displayed in Figure 17.1a and separates eight types of change. (A somewhat similar diagram on page 111, distinguished eight circumstances in which change might be observed—a different system of divisions that is of no use here.) Of the eight boxes set up, four have been discussed, as shown in Figure 17.1b. The two ways of dividing this four-box group are by a horizontal cut or by a vertical cut that separates stars from superscript a’s. (A vertical cut separating the N-box from the rest is of no help; it would be contrary to our theme.) The horizontal cut separates stress-driven effects below from composition-driven effects above. It is in fact the traditional division between mechanics and chemistry; enormous amounts of science fall clearly above the cut or clearly below it and cause no confusion at all. This cut was used as a guide in the early chapters, especially in the flow diagram or organization chart, Figure 8.1. By contrast, the second cut appeared as late as Chapter 15, but deserves emphasis; it is at least as instructive and helpful as the first, and perhaps more helpful.