Converging lines are to be avoided, unless there is something of interest to which you wish to direct attention at the point of convergence. This is by no means an exaggerated specimen of the evil; but the effect of these four arms all converging toward one point is unpleasant. If the personages were disputing over a manuscript, or trying to clutch a bag of gold lying on the table, then the manuscript or the gold would be the centre of interest in the picture; and converging lines would not only be excusable, but absolutely necessary. Where there is nothing of particular interest at the point where the lines meet, the eye feels disappointed at being misled.
Although converging lines are generally to be avoided, it often happens that a repetition of the same kind of curve gives force and unity of purpose to a group. Observe the convex curves formed by the backs of these suppliants. Their repetition gives unity of purpose. A perpendicular kneeling figure might individually be just as expressive, but as one of a group he would take away somewhat from the general character of unity in supplication.
One of the most difficult problems the designer of large mural pictures has to solve, is to introduce with good effect raised arms and hands, especially when they belong to the background figures. When possible, it is better to keep them out of sight altogether; but in some subjects you would by so doing inevitably lose expression and animation, and it becomes necessary to introduce here and there an upraised arm with extended hand. This is easy enough to do if you are reckless about the lines of your composition, but if you are fastidious, it is a very difficult problem.
In the first place, they distract the eye, destroying the full bold outline of your groups, and, secondly, there is a comic element about them which it is rather difficult to avoid. When, as in many of Raffaelle’s Loggie, the whole of the figures which are raising their arms are seen, the effect is bad and trivial; but there is nothing particularly comical about it. When, however, an arm crops up here and there from the unseen figures of the background, it is difficult to avoid the ludicrous. Cases may occur when a whole forest of hands will have to be raised, as in an oath of allegiance; but here the action of raising the arms is inseparable from the subject.
My remarks apply only to upraised arms as indicative of wonder, joy, or grief.
All these hints about designing may appear to some of you rather far-fetched, but if ever you get experience in decorative painting, I think you will find they are not far from the truth.
The art of good grouping is not of spontaneous growth. You may have a general idea of how you are to fill your canvas or wall-space, and that idea may be a good one, but all the details of the groups have to be worked out bit by bit. A change in the attitude of one figure will be almost sure to entail a change in a good many others, and it often happens that, after giving yourself a good deal of trouble, you will have to go back to your first idea.
A conscientious and fastidious designer may be compared to an Arctic explorer picking his way in an ice-pack. He will have to saw through one ice-barrier, to blow up another with gunpowder, to circumvent a third, and when, after surmounting all these difficulties, he thinks his course clear and open water at hand, he may have to retrace his steps and seek some other channel.