In the above example the changes of interval are those of an arithmetical progression.
Fig. 40
In [Fig. 40] the changes of interval are those of a geometrical progression. The movement to the left through these sequences is, no doubt, somewhat checked or prevented by the habit of reading to the right.
Fig. 41
The angle FAB is the angle of vision within which the sequence is observed. At the end F of the sequence there is a greater number of attractions in a given angle of vision than at the end B, so the eye is drawn towards the left. The pull on the eye is greater at the end F because of the greater number and the crowding together of attractions. In the examples just given ([Figs. 39], [40]), we have not only movements in certain directions, but movements in regular and marked measures. The movements are, therefore, rhythmical, according to the definition I have given of Rhythm.
40. It is evident that any relation of positions, balanced or unbalanced, may be substituted for the single dots or points in the figures just given. Such substitutions have the following possibilities.
41. First. When the points lie in a series, at equal intervals, the substitution of a symmetrical group of positions at each point gives no Rhythm, only Harmony.
