The principle once adopted, there seems no limit to the variety of which it is capable. Shafts may be substituted for _all_ of the arch-orders, or for such only of them as may be desired. Where the arch consists of more than two orders, a half-column of larger size may be made to support two or more, and smaller ones may flank them carrying single orders (Fig. 295). Where, again, the lower order is wide in its soffit, it may be carried either by a large semi-column (Fig. 296) or by coupled colonnettes (Fig. 297); and where there are three orders, the same may be applied to the front, bringing the pillars to a uniform design on all of its sides (Figs. 298, 299). [Illustration: Fig. 295. Fig. 296. Fig. 297. Fig. 298. Fig. 299.] We have already seen that single columns may be used to carry arcades of two or more orders, either by breaking their abaci into receding angles, to fit them to the orders of the arches, or by making round or octagonal abaci large enough to receive them; and such single columns may be alternated with clustered piers. There is, however, another extensive variety of pillar compounded of the two. [Illustration: Fig. 300. Fig. 301.] Let us suppose a single column supporting arches of a single order (Fig. 300), and that we desire to extend the arches to _three_ orders, retaining the same main bearing-shaft. We may imagine the additional orders to be super-added on all sides of the original square springer and additional colonnettes (attached or detached) added round the original bearing-shaft to receive them (Fig. 301). The same may be applied to an octagon, placed either angularly or in its usual position (Figs. 302, 303). [Illustration: Fig. 303. Fig. 302. Fig. 304. Fig. 306.] The process may be carried a step farther, and eight colonnettes be set round the original bearing-shaft (Fig. 304). In St. Mary’s Abbey,[35] at York (towards the end of the twelfth century), we have an instance of sixteen colonnettes thus placed round a bearing-shaft (Fig. 305), but only eight of them carry separate orders; and a little later, in the cathedral at Genoa (the work, apparently, of a northern French architect), we have no less than twenty-four colonnettes similarly ranged round an octagon (Fig. 306); though here, again, only eight are represented in the plan of the abacus or of the base when it rests upon the floor, the others being introduced probably for the relief produced by the varied colours of the marbles of which they are composed. [Illustration: Fig. 305.--St. Mary’s Abbey, York.]