The fourth dimension

CHAPTER XI

NOMENCLATURE AND ANALOGIES PRELIMINARY TO THE STUDY OF FOURDIMENSIONAL FIGURES

In the following pages a method of designating different regions of space by a systematic colour scheme has been adopted. The explanations have been given in such a manner as to involve no reference to models, the diagrams will be found sufficient. But to facilitate the study a description of a set of models is given in an appendix which the reader can either make for himself or obtain. If models are used the diagrams in Chapters XI. and XII, will form a guide sufficient to indicate their use. Cubes of the colours designated by the diagrams should be picked out and used to reinforce the diagrams. The reader, in the following description, should suppose that a board or wall stretches away from him, against which the figures are placed. Take a square, one of those shown in Fig. 77 and give it a neutral colour, let this colour be called “null,” and be such that it

makes no appreciable difference 136