§ VII. Before passing to the dripstone, however, let us examine a little farther into the nature of the true cornice. We cannot, indeed, render either of the forms _b_ or _c_, Fig. V., perfectly protective from rain, but we can help them a little in their duty by a slight advance of their upper ledge. This, with the form _b_, we can best manage by cutting off the sharp upper point of its curve, which is evidently weak and useless; and we shall have the form _f_. By a slight advance of the upper stone _c_, we shall have the parallel form _g_. These two cornices, _f_ and _g_, are characteristic of early Byzantine work, and are found on all the most lovely examples of it in Venice. The type _a_ is rarer, but occurs pure in the most exquisite piece of composition in Venice--the northern portico of St. Mark's; and will be given in due time. § VIII. Now the reader has doubtless noticed that these forms of cornice result, from considerations of fitness and necessity, far more neatly and decisively than the forms of the base, which we left only very generally determined. The reason is, that there are many ways of building foundations, and many _good_ ways, dependent upon the peculiar accidents of the ground and nature of accessible materials. There is also room to spare in width, and a chance of a part of the arrangement being concealed by the ground, so as to modify height. But we have no room to spare in width on the top of a wall, and all that we do must be thoroughly visible; and we can but have to deal with bricks, or stones of a certain degree of fineness, and not with mere gravel, or sand, or clay,--so that as the conditions are limited, the forms become determined; and our steps will be more clear and certain the farther we advance. The sources of a river are usually half lost among moss and pebbles, and its first movements doubtful in direction; but, as the current gathers force, its banks are determined, and its branches are numbered. § IX. So far of the true cornice: we have still to determine the form of the dripstone. [Illustration: Fig. VI.]