70. In the repetition of a certain shape-motive in the line, the line may change its direction abruptly or gradually, continuously or alternately, producing a Linear Progression with changes of direction.
Fig. 79
In [Fig. 79] there is a certain change of direction as we pass from one repetition to the next. In the repetition of the same change of direction, of the same angle of divergence, we have Harmony. If the angles of divergence varied we should have no such Harmony, though we might have Harmony in the repetition of a certain relation of divergences. Any repetition of a certain change or changes of direction in a linear progression gives a Harmony of Directions in the progression.
Fig. 80
In this case there is a regular alternation of directions in the repeats. The repeats are drawn first to the right, then up, and the relation of these two directions is then repeated.
71. By inverting the motive of any progression, in single or in double inversion, and repeating the motive together with its inversion, we are able to vary the character of the progression indefinitely.
Fig. 81