In these diagrams of the anatomy of compositions the lines selected are not always very obvious in the originals and are justly much broken into by truths of natural appearance. But an emotional significance depending on some arrangement of abstract lines is to be found underlying the expression in every good picture, carefully hidden as it is by all great artists. And although some apology is perhaps necessary for the ugliness of these diagrams, it is an ugliness that attends all anatomy drawings. If the student will trace them and put his tracing over the reproductions of the originals, they will help him to see on what things in the arrangement the rhythmic force of the picture depends.
Other lines, as important as those selected, may have been overlooked, but the ones chosen will suffice to show the general character of them all.
There is one condition in a composition, that is laid down before you begin, and that is the shape of your panel or canvas. This is usually a rectangular form, and all the lines of your design will have to be considered in relation to this shape. Vertical and horizontal lines being parallel to the boundaries of rectangular pictures, are always right and immediately set up a relationship, as we have seen.
The arresting power of the right angle exists at each corner of a rectangular picture, where the vertical sides meet the horizontal base, and this presents a difficulty, because you do not wish the spectator's attention drawn to the corners, and this dramatic combination of lines always attracts the eye. A favourite way of getting rid of this is to fill them with some dark mass, or with lines swinging round and carrying the eye past them, so that the attention is continually swung to the centre of the picture. For lines have a power of directing the attention, the eye instinctively running with them, and this power is of the greatest service in directing the spectator to the principal interest.
It is this trouble with the corners that makes the problem of filling a square so exacting. In an ordinary rectangular panel you have a certain amount of free space in the middle, and the difficulty of filling the corners comfortably does not present itself until this space is arranged for. But in a square, the moment you leave the centre you are in one or other of the corners, and the filling of them governs the problem much more than in the case of other shapes. It is a good exercise for students to give themselves a square to fill, in order to understand this difficulty and learn to overcome it.
Other lines that possess a direct relation to a rectangular shape are the diagonals. Many compositions that do not hang on a vertical or horizontal basis are built on this line, and are thus related to the bounding shape.
Plate XXXVI.