The fourth dimension

NOMENCLATURE AND ANALOGIES 143

es the yellow cube by a pink square, and touches the white cube by an orange square.

There are three axes to which the colours red, yellow, and white are assigned, the faces of each cube are designated by taking these colours in pairs. Taking all the colours together we get a colour name for the solidity of a cube.

Let us now ask ourselves how the cube could be presented to the plane being. Without going into the question of how he could have a real experience of it, let us see how, if we could turn it about and show it to him, he, under his limitations, could get information about it. If the cube were placed with its red and yellow axes against a plane, that is resting against it by its orange

Null White

ull White Null wh. ace previously perceived

Fig. 87.

face, the plane being would observe a square surrounded by red and yellow lines, and having null points. See the dotted square, fig. 87. We could turn the cube about the red line so that a different face comes into juxtaposition with the plane. Suppose the cube turned about the red line. As it