John Ruskin - The Stones of Venice, Volume 1 (of 3)

§ IV. You will observe, however, that the convexity is to be very slight, and that the shaft is not to bulge in the centre, but to taper from the root in a curved line; the peculiar character of the curve you will discern better by exaggerating, in a diagram, the conditions of its sculpture.

Let a , a , b , b, at A, Fig. XIII., be the rough block of the shaft, laid on the ground; and as thick as you can by any chance require it to be; you will leave it of this full thickness at its base at A, but at the other end you will mark off upon it the diameter c , d, which you intend it to have at the summit; you will then take your mallet and chisel, and working from c and d you will roughly knock off the corners, shaded in the figure, so as to reduce the shaft to the figure described by the inside lines in A and the outside lines in B; you then proceed to smooth it, you chisel away the shaded parts in B, and leave your finished shaft of the form of the inside lines e , g , f , h .

The result of this operation will be of course that the shaft tapers faster towards the top than it does near the ground. Observe this carefully; it is a point of great future importance.

§ V. So far of the shape of detached or block shafts. We can carry the type no farther on merely structural considerations: let us pass to the shaft of inferior materials.

Unfortunately, in practice, this step must be soon made. It is alike difficult to obtain, transport, and raise, block shafts more than ten or twelve feet long, except in remarkable positions, and as pieces of singular magnificence. Large pillars are therefore always composed of more than one block of stone. Such pillars are either jointed like basalt columns, and composed of solid pieces of stone set one above another; or they are filled up towers , built of small stones cemented into a mass, with more or less of regularity: Keep this distinction carefully in mind, it is of great importance; for the jointed column, every stone composing which, however thin, is (so to speak) a complete slice of the shaft, is just as strong as the block pillar of one stone, so long as no forces are brought into action upon it which would have a tendency to cause horizontal dislocation. But the pillar which is built as a filled-up tower is of course liable to fissure in any direction, if its cement give way.

But, in either case, it is evident that all constructive reason of the curved contour is at once destroyed. Far from being an easy or natural procedure, the fitting of each portion of the curve to its fellow, in the separate stones, would require painful care and considerable masonic skill; while, in the case of the filled-up tower, the curve outwards would be even unsafe; for its greatest strength (and that the more in proportion to its careless building) lies in its bark, or shell of 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 æsthetic laws only.

§ VI. 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.

§ VII. 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, cæteris 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 suggested itself to a people who possessed no large blocks out of which to hew them; and that the shaft built of many pieces is probably derived from, and imitative of the shaft hewn from few or from one.

§ VIII. If, therefore, you take a good geological map of Europe, and lay your finger upon the spots where volcanic influences supply either travertin or marble in accessible and available masses, you will probably mark the points where the types of the first school have been originated and developed. If, in the next place, you will mark the districts where broken and rugged basalt or whinstone, or slaty sandstone, supply materials on easier terms indeed, but fragmentary and unmanageable, you will probably distinguish some of the birthplaces of the derivative and less graceful school. You will, in the first case, lay your finger on Pæstum, Agrigentum, and Athens; in the second, on Durham and Lindisfarne.

The shafts of the great primal school are, indeed, in their first form, as massy as those of the other, and the tendency of both is to continual diminution of their diameters: but in the first school it is a true diminution in the thickness of the independent pier; in the last, it is an apparent diminution, obtained by giving it the appearance of a group of minor piers. The distinction, however, with which we are concerned is not that of slenderness, but of vertical or curved contour; and we may note generally that while throughout the whole range of Northern work, the perpendicular shaft appears in continually clearer development, throughout every group which has inherited the spirit of the Greek, the shaft retains its curved or tapered form; and the occurrence of the vertical detached shaft may at all times, in European architecture, be regarded as one of the most important collateral evidences of Northern influence.

§ IX. It is necessary to limit this observation to European architecture, because the Egyptian shaft is often untapered, like the Northern. It appears that the Central Southern, or Greek shaft, was tapered or curved on æsthetic rather than constructive principles; and the Egyptian which precedes, and the Northern which follows it, are both vertical, the one because the best form had not been discovered, the other because it could not be attained. Both are in a certain degree barbaric; and both possess in combination and in their ornaments a power altogether different from that of the Greek shaft, and at least as impressive if not as admirable.

§ X. We have hitherto spoken of shafts as if their number were fixed, and only their diameter variable according to the weight to be borne. But this supposition is evidently gratuitous; for the same weight may be carried either by many and slender, or by few and massy shafts. If the reader will look back to Fig. IX., he will find the number of shafts into which the wall was reduced to be dependent altogether upon the length of the spaces a , b , a , b , &c., a length which was arbitrarily fixed. We are at liberty to make these spaces of what length we choose, and, in so doing, to increase the number and diminish the diameter of the shafts, or vice versâ .