CONSTRUCTION VIII. THE SHAFT 117

outside stone; and this, if curved outwards, would at once burst outwards if heavily loaded above.

If, therefore, the curved outline be ever retained in such shafts, it must be in obedience to ęsthetic laws only.

§ 6. But farther. Not only the curvature, but even the tapering by straight lines, would be somewhat difficult of execution in the pieced column. Where, indeed, the entire shaft is composed of four or five blocks set one upon another, the diameters may be easily determined at the successive joints, and the stones chiselled to the same slope. But this becomes sufficiently troublesome when the joints are numerous, so that the pillar is like a pile of cheeses; or when it is to be built of small and irregular stones. We should be naturally led, in the one case, to cut all the cheeses to the same diameter; in the other, to build by the plumb-line; and, in both, to give up the tapering altogether.

§ 7. Farther. Since the chance, in the one case, of horizontal dislocation, in the other, of irregular fissure, is much increased by the composition of the shaft out of joints or small stones, a larger bulk of shaft is required to carry the given weight; and cęteris paribus, jointed and cemented shafts must be thicker in proportion to the weight they carry than those which are of one block.

We have here evidently natural causes of a very marked division in schools of architecture: one group composed of buildings whose shafts are either of a single stone or of few joints; the shafts, therefore, being gracefully tapered, and reduced by successive experiments to the narrowest possible diameter proportioned to the weight they carry: and the other group embracing those buildings whose shafts are of many joints or of small stones; shafts which are therefore not tapered, and rather thick and ponderous in proportion to the weight they carry; the latter school being evidently somewhat imperfect and inelegant as compared with the former.

It may perhaps appear, also, that this arrangement of the materials in cylindrical shafts at all would hardly have

[Version 0.04: March 2008]