Externally, however, the madness of this engineering feat does not trouble one. The addition of the tower and spire gives to the whole composition that pyramidal outline which always presents such a satisfactory appearance of stability to the eye—and in architectural design it is the eye that has to be reckoned with. In Wren’s masterpiece, St. Paul’s, one has the same central pyramidal outline of all the masses, but in a still higher degree. [Illustration: NAVE AND WEST FRONT.] In both cases, in St. Paul’s and in Salisbury, unity is secured. Salisbury spire is tall enough, St. Paul’s dome is tall and broad enough, to impose unity on all the diverging masses of the building. The low towers of Worcester and Hereford have no such supreme dominance. Next to the abiding presence of the spire, unity is secured by scoring strong, horizontal lines round the building, welding its masses into one composition. Most cathedrals are contented, like Wells, with one strong horizontal line—a broad parapet. But at Salisbury there is not only a horizontal parapet, but a horizontal corbel-table as well; and there are no less than three horizontal strings—one running round the base of the walls, a second running along beneath the windows, and a third running round the buttresses; moreover, each of these horizontal lines is scored far more heavily than anywhere else. Especially remarkable is it to find the upper flow of the buttresses stopped by a heavy string. Usually, in Gothic, if a horizontal meets a vertical line, the former gives way; here, as in Greek architecture, the vertical gives way to the horizontal line. This architect saw, what few others of his day saw, that you may make too much of the “aspiring principle” of Gothic; that if you suppress the horizontal lines, you weaken the unity of the building, by failing to tie all its parts together. As we have seen, the appearance of stability was enhanced by the pyramidal outline which the whole building ultimately assumed. But the eye instinctively looks downwards also to see that the pyramidal outline is continued there, it instinctively demands an emphatic spreading base. It likes to see a rock-like foundation. At Salisbury all below is but greensward. All the more carefully, therefore, has the builder spread out and broadened and emphasised his base-courses, till art gives the appearance of stability which nature has denied. [Illustration: WEST FRONT]