§ I. There are no features to which the attention of architects has been more laboriously directed, in all ages, than these crowning members of the wall and shaft; and it would be vain to endeavor, within any moderate limits, to give the reader any idea of the various kinds of admirable decoration which have been invented for them. But, in proportion to the effort and straining of the fancy, have been the extravagances into which it has occasionally fallen; and while it is utterly impossible severally to enumerate the instances either of its success or its error, it is very possible to note the limits of the one and the causes of the other. This is all that we shall attempt in the present chapter, tracing first for ourselves, as in previous instances, the natural channels by which invention is here to be directed or confined, and afterwards remarking the places where, in real practice, it has broken bounds. § II. The reader remembers, I hope, the main points respecting the cornice and capital, established above in the Chapters on Construction. Of these I must, however, recapitulate thus much:-- 1. That both the cornice and capital are, with reference to the _slope_ of their profile or bell, to be divided into two great orders; in one of which the ornament is convex, and in the other concave. (Ch. VI., § V.) 2. That the capital, with reference to the method of twisting the cornice round to construct it, and to unite the circular shaft with the square abacus, falls into five general forms, represented in Fig. XXII., p. 119. 3. That the most elaborate capitals were formed by true or simple capitals with a common cornice added above their abacus. (Ch. IX., § XXIV.) We have then, in considering decoration, first to observe the treatment of the two great orders of the cornice; then their gathering into the five of the capital; then the addition of the secondary cornice to the capital when formed. § III. The two great orders or families of cornice were above distinguished in Fig. V., p. 69.; and it was mentioned in the same place that a third family arose from their combination. We must deal with the two great opposed groups first.