§ XV. I have said nothing yet of the proportion of the height of Yb to its width, nor of that of Yb and Xb to each other. Both depend much on the height of shaft, and are besides variable within certain limits, at the architect’s discretion. But the limits of the height of Yb may be thus generally stated. If it looks so thin as that the weight of the column above might break it, it is too low; and if it is higher than its own width, it is too high. The utmost admissible height is that of a cubic block; for if it ever become higher than it is wide, it becomes itself a part of a pier, and not the base of one.
§ XVI. I have also supposed Yb, when expanded from beneath Xb, as always expanded into a square, and four spurs only to be added at the angles. But Yb may be expanded into a pentagon, hexagon, or polygon; and Xb then may have five, six, or many spurs. In proportion, however, as the sides increase in number, the spurs become shorter and less energetic in their effect, and the square is in most cases the best form.
§ XVII. We have hitherto conducted the argument entirely on the supposition of the pillars being numerous, and in a range. Suppose, however, that we require only a single pillar: as we have free space round it, there is no need to fill up the first ranges of its foundations; nor need we do so in order to equalise pressure, since the pressure to be met is its own alone. Under such circumstances, it is well to exhibit the lower tiers of the foundation as well as Yb and Xb. The noble bases of the two granite pillars of the Piazzetta at Venice are formed by the entire series of members given in Fig. X., the lower courses expanding into steps, with a superb breadth of proportion to the shaft. The member Xb is of course circular, having its proper decorative mouldings, not here considered; Yb is octagonal, but filled up into a square by certain curious groups of figures representing the trades of Venice. The three courses below are octagonal, with their sides set across the angles of the innermost octagon, Yb. The shafts are 15 feet in circumference, and the lowest octagons of the base 56 (7 feet each side).
§ XVIII. Detached buildings, like our own Monument, are not pillars, but towers built in imitation of Pillars. As towers they are barbarous, being dark, inconvenient, and unsafe, besides lying, and pretending to be what they are not. As shafts they are barbarous, because they were designed at a time when the Renaissance architects had introduced and forced into acceptance, as de rigueur, a kind of columnar high-heeled shoe,—a thing which they called a pedestal, and which is to a true base exactly what a Greek actor’s cothurnus was to a Greek gentleman’s sandal. But the Greek actor knew better, I believe, than to exhibit or to decorate his cork sole; and, with shafts as with heroes, it is rather better to put the sandal off than the cothurnus on. There are, indeed, occasions on which a pedestal may be necessary; it may be better to raise a shaft from a sudden depression of plinth to a level with others, its companions, by means of a pedestal, than to introduce a higher shaft; or it may be better to place a shaft of alabaster, if otherwise too short for our purpose, on a pedestal, than to use a larger shaft of coarser material; but the pedestal is in each case a make-shift, not an additional perfection. It may, in the like manner, be sometimes convenient for men to walk on stilts, but not to keep their stilts on as ornamental parts of dress. The bases of the Nelson Column, the Monument, and the column of the Place Vendôme, are to the shafts, exactly what highly ornamented wooden legs would be to human beings.
§ XIX. So far of bases of detached shafts. As we do not yet know in what manner shafts are likely to be grouped, we can say nothing of those of grouped shafts until we know more of what they are to support.
Lastly; we have throughout our reasoning upon the base supposed the pier to be circular. But circumstances may occur to prevent its being reduced to this form, and it may remain square or rectangular; its base will then be simply the wall base following its contour, and we have no spurs at the angles. Thus much may serve respecting pier bases; we have next to examine the concentration of the Wall Veil, or the Shaft.
CHAPTER VIII.
THE SHAFT
§ I. We have seen in the last Chapter how, in converting the wall into the square or cylindrical shaft, we parted at every change of form with some quantity of material. In proportion to the quantity thus surrendered, is the necessity that what we retain should be good of its kind, and well set together, since everything now depends on it.
It is clear also that the best material, and the closest concentration, is that of the natural crystalline rocks; and that, by having reduced our wall into the shape of shafts, we may be enabled to avail ourselves of this better material, and to exchange cemented bricks for crystallised blocks of stone. Therefore, the general idea of a perfect shaft is that of a single stone hewn into a form more or less elongated and cylindrical. Under this form, or at least under the ruder one of a long stone set upright, the conception of true shafts appears first to have occurred to the human mind; for the reader must note this carefully, once for all, it does not in the least follow that the order of architectural features which is most reasonable in their arrangement, is most probable in their invention. I have theoretically deduced shafts from walls, but shafts were never so reasoned out in architectural practice. The man who first propped a thatched roof with poles was the discoverer of their principle; and he who first hewed a long stone into a cylinder, the perfecter of their practice.
§ II. It is clearly necessary that shafts of this kind (we will call them, for convenience, block shafts) should be composed of stone not liable to flaws or fissures; and therefore that we must no longer continue our argument as if it were always possible to do what is to be done in the best way; for the style of a national architecture may evidently depend, in great measure, upon the nature of the rocks of the country.
Our own English rocks, which supply excellent building stone from their thin and easily divisible beds, are for the most part entirely incapable of being worked into shafts of any size, except only the granites and whinstones, whose hardness renders them intractable for ordinary purposes;—and English architecture therefore supplies no instances of the block shaft applied on an extensive scale; while the facility of obtaining large masses of marble has in Greece and Italy been partly the cause of the adoption of certain noble types of architectural form peculiar to those countries, or, when occurring elsewhere, derived from them.
We have not, however, in reducing our walls to shafts, calculated on the probabilities of our obtaining better materials than those of which the walls were built; and we shall therefore first consider the form of shaft which will be best when we have the best materials; and then consider how far we can imitate, or how far it will be wise to imitate, this form with any materials we can obtain.
§ III. Now as I gave the reader the ground, and the stones, that he might for himself find out how to build his wall, I shall give him the block of marble, and the chisel, that he may himself find out how to shape his column. Let him suppose the elongated mass, so given him, rudely hewn to the thickness which he has calculated will be proportioned to the weight it has to carry. The conditions of stability will require that some allowance be made in finishing it for any chance of slight disturbance or subsidence of the ground below, and that, as everything must depend on the uprightness of the shaft, as little chance should be left as possible of its being thrown off its balance. It will therefore be prudent to leave it slightly thicker at the base than at the top. This excess of diameter at the base being determined, the reader is to ask himself how most easily and simply to smooth the column from one extremity to the other. To cut it into a true straight-sided cone would be a matter of much trouble and nicety, and would incur the continual risk of chipping into it too deep. Why not leave some room for a chance stroke, work it slightly, very slightly convex, and smooth the curve by the eye between the two extremities? you will save much trouble and time, and the shaft will be all the stronger.
Fig. XIII.
This is accordingly the natural form of a detached block shaft. It is the best. No other will ever be so agreeable to the mind or eye. I do not mean that it is not capable of more refined execution, or of the application of some of the laws of æsthetic beauty, but that it is the best recipient of execution and subject of law; better in either case than if you had taken more pains, and cut it straight.
§ 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.
§ XI. Supposing the materials are in each case to be of the same kind, the choice is in great part at the architect’s discretion, only there is a limit on the one hand to the multiplication of the slender shaft, in the inconvenience of the narrowed interval, and on the other, to the enlargement of the massy shaft, in the loss of breadth to the building.38 That will be commonly the best proportion which is a natural mean between the two limits; leaning to the side of grace or of grandeur according to the expressional intention of the work. I say, commonly the best, because, in some cases, this expressional invention may prevail over all other considerations, and a column of unnecessary bulk or fantastic slightness be adopted in order to strike the spectator with awe or with surprise.39 The architect is, however, rarely in practice compelled to use one kind of material only; and his choice lies frequently between the employment of a larger number of solid and perfect small shafts, or a less number of pieced and cemented large ones. It is often possible to obtain from quarries near at hand, blocks which might be cut into shafts eight or twelve feet long and four or five feet round, when larger shafts can only be obtained in distant localities; and the question then is between the perfection of smaller features and the imperfection of larger. We shall find numberless instances in Italy in which the first choice has been boldly, and I think most wisely made; and magnificent buildings have been composed of systems of small but perfect shafts, multiplied and superimposed. So long as the idea of the symmetry of a perfect shaft remained in the builder’s mind, his choice could hardly be directed otherwise, and the adoption of the built and tower-like shaft appears to have been the result of a loss of this sense of symmetry consequent on the employment of intractable materials.
§ XII. But farther: we have up to this point spoken of shafts as always set in ranges, and at equal intervals from each other. But there is no necessity for this; and material differences may be made in their diameters if two or more be grouped so as to do together the work of one large one, and that within, or nearly within, the space which the larger one would have occupied.
§ XIII. Let A, B, C, Fig. XIV., be three surfaces, of which B and C contain equal areas, and each of them double that of A: then supposing them all loaded to the same height, B or C would receive twice as much weight as A; therefore, to carry B or C loaded, we should need a shaft of twice the strength needed to carry A. Let S be the shaft required to carry A, and S2 the shaft required to carry B or C; then S3 may be divided into two shafts, or S2 into four shafts, as at S3, all equal in area or solid contents;40 and the mass A might be carried safely by two of them, and the masses B and C, each by four of them.
Fig. XIV.
Now if we put the single shafts each under the centre of the mass they have to bear, as represented by the shaded circles at a, a2, a3, the masses A and C are both of them very ill supported, and even B insufficiently; but apply the four and the two shafts as at b, b2, b3, and they are supported satisfactorily. Let the weight on each of the masses be doubled, and the shafts doubled in area, then we shall have such arrangements as those at c, c2, c3; and if again the shafts and weight be doubled, we shall have d, d2, d3.
§ XIV. Now it will at once be observed that the arrangement of the shafts in the series of B and C is always exactly the same in their relations to each other; only the group of B is set evenly, and the group of C is set obliquely,—the one carrying a square, the other a cross.
Fig. XV.
You have in these two series the primal representations of shaft arrangement in the Southern and Northern schools; while the group b, of which b2 is the double, set evenly, and c2 the double, set obliquely, is common to both. The reader will be surprised to find how all the complex and varied forms of shaft arrangement will range themselves into one or other of these groups; and still more surprised to find the oblique or cross set system on the one hand, and the square set system on the other, severally distinctive of Southern and Northern work. The dome of St. Mark’s, and the crossing of the nave and transepts of Beauvais, are both carried by square piers; but the piers of St. Mark’s are set square to the walls of the church, and those of Beauvais obliquely to them: and this difference is even a more essential one than that between the smooth surface of the one and the reedy complication of the other. The two squares here in the margin (Fig. XV.) are exactly of the same size, but their expression is altogether different, and in that difference lies one of the most subtle distinctions between the Gothic and Greek spirit,—from the shaft, which bears the building, to the smallest decoration. The Greek square is by preference set evenly, the Gothic square obliquely; and that so constantly, that wherever we find the level or even square occurring as a prevailing form, either in plan or decoration, in early northern work, there we may at least suspect the presence of a southern or Greek influence; and, on the other hand, wherever the oblique square is prominent in the south, we may confidently look for farther evidence of the influence of the Gothic architects. The rule must not of course be pressed far when, in either school, there has been determined search for every possible variety of decorative figures; and accidental circumstances may reverse the usual system in special cases; but the evidence drawn from this character is collaterally of the highest value, and the tracing it out is a pursuit of singular interest. Thus, the Pisan Romanesque might in an instant be pronounced to have been formed under some measure of Lombardic influence, from the oblique squares set under its arches; and in it we have the spirit of northern Gothic affecting details of the southern;—obliquity of square, in magnificently shafted Romanesque. At Monza, on the other hand, the levelled square is the characteristic figure of the entire decoration of the façade of the Duomo, eminently giving it southern character; but the details are derived almost entirely from the northern Gothic. Here then we have southern spirit and northern detail. Of the cruciform outline of the load of the shaft, a still more positive test of northern work, we shall have more to say in the 28th Chapter; we must at present note certain farther changes in the form of the grouped shaft, which open the way to every branch of its endless combinations, southern or northern.
Fig. XVI.
§ XV. 1. If the group at d3, Fig. XIV., be taken from under its loading, and have its centre filled up, it will become a quatrefoil; and it will represent, in their form of most frequent occurrence, a family of shafts, whose plans are foiled figures, trefoils, quatrefoils, cinquefoils, &c.; of which a trefoiled example, from the Frari at Venice, is the third in Plate II., and a quatrefoil from Salisbury the eighth. It is rare, however, to find in Gothic architecture shafts of this family composed of a large number of foils, because multifoiled shafts are seldom true grouped shafts, but are rather canaliculated conditions of massy piers. The representatives of this family may be considered as the quatrefoil on the Gothic side of the Alps; and the Egyptian multifoiled shaft on the south, approximating to the general type, b, Fig. XVI.
§ XVI. Exactly opposed to this great family is that of shafts which have concave curves instead of convex on each of their sides; but these are not, properly speaking, grouped shafts at all, and their proper place is among decorated piers; only they must be named here in order to mark their exact opposition to the foiled system. In their simplest form, represented by c, Fig. XVI., they have no representatives in good architecture, being evidently weak and meagre; but approximations to them exist in late Gothic, as in the vile cathedral of Orleans, and in modern cast-iron shafts. In their fully developed form they are the Greek Doric, a, Fig. XVI., and occur in caprices of the Romanesque and Italian Gothic: d, Fig. XVI., is from the Duomo of Monza.
§ XVII. 2. Between c3 and d3 of Fig. XIV. there may be evidently another condition, represented at 6, Plate II., and formed by the insertion of a central shaft within the four external ones. This central shaft we may suppose to expand in proportion to the weight it has to carry. If the external shafts expand in the same proportion, the entire form remains unchanged; but if they do not expand, they may (1) be pushed out by the expanding shaft, or (2) be gradually swallowed up in its expansion, as at 4, Plate II. If they are pushed out, they are removed farther from each other by every increase of the central shaft; and others may then be introduced in the vacant spaces; giving, on the plan, a central orb with an ever increasing host of satellites, 10, Plate II.; the satellites themselves often varying in size, and perhaps quitting contact with the central shaft. Suppose them in any of their conditions fixed, while the inner shaft expands, and they will be gradually buried in it, forming more complicated conditions of 4, Plate II. The combinations are thus altogether infinite, even supposing the central shaft to be circular only; but their infinity is multiplied by many other infinities when the central shaft itself becomes square or crosslet on the section, or itself multifoiled (8, Plate II.) with satellite shafts eddying about its recesses and angles, in every possible relation of attraction. Among these endless conditions of change, the choice of the architect is free, this only being generally noted: that, as the whole value of such piers depends, first, upon their being wisely fitted to the weight above them, and, secondly, upon their all working together: and one not failing the rest, perhaps to the ruin of all, he must never multiply shafts without visible cause in the disposition of members superimposed:41 and in his multiplied group he should, if possible, avoid a marked separation between the large central shaft and its satellites; for if this exist, the satellites will either appear useless altogether, or else, which is worse, they will look as if they were meant to keep the central shaft together by wiring or caging it in; like iron rods set round a supple cylinder,—a fatal fault in the piers of Westminster Abbey, and, in a less degree, in the noble nave of the cathedral of Bourges.
§ XVIII. While, however, we have been thus subdividing or assembling our shafts, how far has it been possible to retain their curved or tapered outline? So long as they remain distinct and equal, however close to each other, the independent curvature may evidently be retained. But when once they come in contact, it is equally evident that a column, formed of shafts touching at the base and separate at the top, would appear as if in the very act of splitting asunder. Hence, in all the closely arranged groups, and especially those with a central shaft, the tapering is sacrificed; and with less cause for regret, because it was a provision against subsidence or distortion, which cannot now take place with the separate members of the group. Evidently, the work, if safe at all, must be executed with far greater accuracy and stability when its supports are so delicately arranged, than would be implied by such precaution. In grouping shafts, therefore, a true perpendicular line is, in nearly all cases, given to the pier; and the reader will anticipate that the two schools, which we have already found to be distinguished, the one by its perpendicular and pieced shafts, and the other by its curved and block shafts, will be found divided also in their employment of grouped shafts;—it is likely that the idea of grouping, however suggested, will be fully entertained and acted upon by the one, but hesitatingly by the other; and that we shall find, on the one hand, buildings displaying sometimes massy piers of small stones, sometimes clustered piers of rich complexity, and on the other, more or less regular succession of block shafts, each treated as entirely independent of those around it.
§ XIX. Farther, the grouping of shafts once admitted, it is probable that the complexity and richness of such arrangements would recommend them to the eye, and induce their frequent, even their unnecessary introduction; so that weight which might have been borne by a single pillar, would be in preference supported by four or five. And if the stone of the country, whose fragmentary character first occasioned the building and piecing of the large pier, were yet in beds consistent enough to supply shafts of very small diameter, the strength and simplicity of such a construction might justify it, as well as its grace. The fact, however, is that the charm which the multiplication of line possesses for the eye has always been one of the chief ends of the work in the grouped schools; and that, so far from employing the grouped piers in order to the introduction of very slender block shafts, the most common form in which such piers occur is that of a solid jointed shaft, each joint being separately cut into the contour of the group required.