§ IX. Further, and finally. In proportion to the height and size of the building, and therefore to the size of its doors, will be the thickness of its walls, especially at the foundation, that is to say, beside the doors; and also in proportion to the numbers of a crowd will be the unruliness and pressure of it. Hence, partly in necessity and partly in prudence, the splaying or chamfering of the jamb of the larger door will be deepened, and, if possible, made at a larger angle for the large door than for the small one; so that the large door will always be encompassed by a visible breadth of jamb proportioned to its own magnitude. The decorative value of this feature we shall see hereafter. § X. The second kind of apertures we have to examine are those of windows. Window apertures are mainly of two kinds; those for outlook, and those for inlet of light, many being for both purposes, and either purpose, or both, combined in military architecture with those of offence and defence. But all window apertures, as compared with door apertures, have almost infinite licence of form and size: they may be of any shape, from the slit or cross slit to the circle;[56] of any size, from the loophole of the castle to the pillars of light of the cathedral apse. Yet, according to their place and purpose, one or two laws of fitness hold respecting them, which let us examine in the two classes of windows successively, but without reference to military architecture, which here, as before, we may dismiss as a subject of separate science, only noticing that windows, like all other features, are always delightful, if not beautiful, when their position and shape have indeed been thus necessarily determined, and that many of their most picturesque forms have resulted from the requirements of war. We should also find in military architecture the typical forms of the two classes of outlet and inlet windows in their utmost development; the greatest sweep of sight and range of shot on the one hand, and the fullest entry of light and air on the other, being constantly required at the smallest possible apertures. Our business, however, is to reason out the laws for ourselves, not to take the examples as we find them.