The famous Bull of Paul Potter (149), in the Royal Museum at the Hague, furnishes a third type, the diagonal.  High on one side are grouped the herdsman, leaning on a tree which fills up the sky on that side, and his three sheep and cow.  The head of the bull is turned toward this side, and his back and hind leg slope down to the other side, as the ground slopes away to a low distant meadow.  The picture is thus divided by an irregular diagonal.  Somewhat more regular is the diagonal of the Evening Landscape, by Cuyp (348), in the Buckingham Palace, London.  High trees and cliffs, horsemen and others, occupy one side, and the mountains in the background, the ground and the clouds, all slope gradually down to the other side.

It is a natural transition from this type to the V-shape of the landscapes by Aart van der Neer, Dutch Villages, 245 and 420, in the London National Gallery and in the Rudolphinum at Prague, respectively.  Here are trees and houses on each side, gradually sloping to the center to show an open sky and deep vista.  Other examples, of course, show the opening not exactly in the center.

In the Concert by Giorgione (758), in the Pitti Gallery, Florence, is seen the less frequent type of the square.  The three figures turned toward each other with heads on the same level make almost a square space-shape, although it might be said that the central player gives a pyramidal foundation.  This last may also be said of Verrocchio’s Tobias and the Archangels in the Florence Academy, for the square, or rather rectangle, is again lengthened by the pyramidal shape of the two central figures.  The unrelieved square, it may here be interpolated, is not often found except in somewhat primitive examples.  Still less often observed is the oval type of Samson’s Wedding feast, Rembrandt (295), in the Royal Gallery, Dresden.  Here one might, by pressing the interpretation, see an obtuse-angled double-pyramid with the figure of Delilah for an apex, but a few very irregular pictures seem to fall best under the given classification.

Last of all it must be remarked that the great majority of pictures show a combination of two or even three types; but these are usually subordinated to one dominant type.  Such, for instance, is the case with many portraits, which are markedly pyramidal, with the double-pyramid suggested by the position of the arms, and the inverted pyramid, or V, in the landscape background.  The diagonal sometimes just passes over into the V, or into the pyramid; or the square is combined with both.

It is, of course, not necessary at this point to show how it is that such an apparently unsymmetrical shape as the diagonal, alone or in combination with other forms, nevertheless produces an effect of balance.  In all these cases of the diagonal type the mass or interest of the one side, or the direction of subordinate lines backward to it, balances the impulse of the line descending to the other side.  The presence of balance or substitutional symmetry is taken for granted in this treatment, having been previously established, and only the modifications of this symmetry are under consideration.