The fourth dimension

140 THE FOURTH DIMENSION

right from the null on the left we have a change involving the introduction of white, while the yellow change runs from front to back. There are three colour axes—the red,

Fig. 82.

the white, the yellow—and these run in the position the cubes occupy in the drawing—up, to the right, away—but they could be turned about to occupy any positions in space.

Third layer,

Second layer.

We can conveniently represent a block of cubes by three sets of squares, representing each the base of a cube. Thus the block, fig. 83, can be represented by the