The fourth dimension

192 THE FOURTH DIMENSION From this section a cube goes off in the fourth dimen-

sion, which is formed by moving each point of the section in the blue direction.

Pink 4 43 Yellow 4 Null_White Light blue White Fig. 115. Fig. 116.

Drawing this cube we have fig. 116.

Now this cube occurs as a series of sections in our original representation of the tesseract. Taking four steps as before this cube appears as the sections drawn in Bo, &, bs, bs, by, fig. 117, and if the line 4 is subjected to a movement equal in the blue and yellow directions, it will occupy the positions designated by 4, 4,, 42, 43, 44

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Fig. “an

Hence, reasoning in a similar manner about every line, it is evident that, moved equally in the blue and yellow directions, the pink plane will trace out a space which is shown by the series of section planes represented in the diagram.

Thus the space traced out by the pink face, if it is moved equally in the yellow and blue directions, is represented by the set of planes delineated in Fig. 118, pink

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