38. In any unsymmetrical relation of positions (directions, distances,
intervals), in which the balance-center is not clearly and sufficiently
indicated, there is a suggestion of movement. The eye, not being held
by any balance, readily follows this suggestion.
[Illustration: Fig. 36]
In this case we feel that the group of dots is unbalanced in character
and unstable in its position or attitude. It is easy, inevitable
indeed, to imagine the group falling away to the right. This is due,
no doubt, to the visual habit of imagining a base-line when it is not
drawn. Our judgments are constantly made with reference to the imagined
standards of verticality and horizontality. We seem to be provided with
a plumb-line and a level without being conscious of the fact.
[Illustration: Fig. 37]
In this case there is a suggestion of falling down to the left due
to the feeling of instability. A symmetrical framing holding the eye
at the center of equilibrium would prevent the feeling of movement,
provided the framing were sufficiently strong in its attractions. In
the examples I have given (Fig. 36 and Fig. 37) we have movement, but
no Rhythm.
39. There is another type of movement which we must consider,—the
type of movement which is caused by a gradual crowding together of
attractions.
[Illustration: Fig. 38]
There is nothing in this series of dots but the harmony of
corresponding attractions and intervals repeated in a harmony of
direction. If, instead of the repetition of equal intervals, we had a
regular progression of intervals, either arithmetical or geometrical,
we should feel a movement in the direction of diminishing intervals.
[Illustration: Fig. 39]
In the above example the changes of interval are those of an
arithmetical progression.
[Illustration: 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.
[Illustration: 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.
[Illustration: Fig. 42]
There is no movement in this series of repetitions. There is
consequently no Rhythm. Disregarding the habit of reading to the right,
which induces the eye to move in that direction, it is as easy to move
toward the left as toward the right. It requires more than repetitions
at equal intervals to produce the feeling of Rhythm. There must be
movement, and the movement must have a definite direction.
42. Second. The substitution at each point of a symmetrical group at
equal intervals, as before, but with a progressive change of scale,
will give us Rhythm. The movement will be due to the gradual crowding
together of attractions at one end of the series.
[Illustration: Fig. 43]
In this case we have the repetition of a symmetrical relation of
positions at equal intervals with a gradation of scale in the
repetitions. The result is a Rhythm, in which the movement is from left
to right, owing to the greater crowding together of attractions at the
right end of the series. The feeling of Rhythm is no doubt somewhat
enhanced by our habit of reading to the right, which facilitates the
movement of the eye in that direction.
43. Third. The substitution of an unstable group at each point of the
sequence, the repetitions being at equal intervals, gives us a Rhythm,
due simply to the movement of the group itself, which is unstable.
[Illustration: Fig. 44]
Taking the relation of positions given in Fig. 36 and repeating it at
equal intervals, it will be observed that the falling-to-the-right
movement, which is the result of instability, is conveyed to the whole
series of repetitions. To make it perfectly clear that the movement of
this Rhythm is due to the suggestion of movement in the relation of
positions which is repeated, I will ask the reader to compare it with
the repetition of a symmetrical group in Fig. 42. There is no movement
in that case, therefore no Rhythm.
44. Fourth. The movement in Fig. 44 may be increased by a diminution
of scale and consequent crowding together of the dots, provided
the movement of the groups and the crowding together have the same
direction.
[Illustration: Fig. 45]
In this case, as I have said, the movement of Fig. 44 is enforced by
the presence of another element of movement, that of a gradation of
scale and consequent crowding together in the groups. The two movements
have the same direction. The movement of the crowding is not so strong
as that which is caused by the instability of the group itself.
45. Fifth. A symmetrical relation of positions, being repeated in a
series with gradually diminishing intervals between the repeats, will
give us a feeling of rhythmic movement. It will be due to a gradual
increase in the number of attractions as the eye passes from one angle
of vision to another. See Fig. 41. The Rhythm will, no doubt, be
somewhat retarded by the sense of successive axes of symmetry.
[Illustration: Fig. 46]
In this case a symmetrical group is repeated in a progression of
measures. The movement is toward the greater number of attractions at
the right end of the series. This increase in the number of attractions
is due simply to diminishing intervals in that direction. The eye
moves through a series of angles toward the angle which contains the
greatest number of attractions. The reader can hardly fail to feel the
successive axes of symmetry as a retarding element in this Rhythm.
46. Sixth. Symmetrical relations of position may be repeated in
progressions of scale and of intervals. In that case we get two
movements, one caused by a gradual increase in the number of
attractions in successive angles of vision, the other being due to a
gradual crowding together and convergence of attractions in the same
series of angles.
[Illustration: Fig. 47]
Comparing this Rhythm with the Rhythm of Fig. 43, the reader will
appreciate the force of a diminution of scale in connection with a
diminution of intervals.
47. Seventh. Unstable groups may be repeated in progressions of
intervals, in which case the movement in the group is conveyed to the
whole series, in which there will be, also, the movement of a gradual
increase of attractions from one angle of vision to another. In all
such cases contrary motion should be avoided if the object is Rhythm.
The several movements should have a harmony of direction.
[Illustration: Fig. 48]
In this case the movement in the group is felt throughout the series,
and the force of the movement is enhanced by the force of a gradual
increase of attractions from one visual angle to another, in the same
direction, to the right. By reversing the direction of increasing
attractions and so getting the two movements into contrary motion, the
feeling of rhythm would be much diminished. Such contrary motions are
unsatisfactory unless Balance can be achieved. In that case all sense
of movement and of rhythm disappears.
48. Eighth. Unstable groups may be repeated, not only in a gradation
of intervals, but in a gradation of scale, in which case we have a
combination of three causes of movement: lack of stability in the
group repeated, a gradual increase in the number of attractions in
the sequence of visual angles, and a crowding or convergence of the
attractions. Rhythms of this type will not be satisfactory unless the
three movements have the same direction.
[Illustration: Fig. 49]
Here we have the repetition of an unstable group of attractions in a
progression of scale and also of intervals. The arrangement gives us
three elements of movement, all in the same direction.
49. Two or even more of such rhythms as I have described may be
combined in one compound rhythm, in which the eye will follow two
or more distinct movements at the same time. It is important in all
compound rhythms that there should be no opposition or conflict of
movements, unless of course the object is to achieve a balance of
contrary movements. Corresponding rhythms in contrary motion balance
one another. If one of the movements is to the right, the other to the
left, the balance will be symmetrical.