The fourth dimension

156 THE FOURTH DIMENSION

taken, and imagine each section to come in successively, taking the place of the preceding one.

These sections appear to the plane being, counting from the first, to exactly coincide each with the preceding one. But the section of the string occupies a different place in each to that which it does in the preceding section. The section of the string appears in the position marked by the dots. Hence the slant of the string appears as a motion in the frame work marked out by the cube sides. If we suppose the motion of the cube not to be recognised, then the string appears to the plane being as a moving point. Hence extension on the unknown dimension appears as duration. Extension sloping in the unknown direction appears as continuous movement.