I. Thus far we have been concerned with the outline only of the aperture: we were next, it will be remembered, to consider the necessary modes of filling it with valves in the case of the door, or with glass or tracery in that of the window.
1. Fillings of doors. We concluded, in the previous Chapter, that doors in buildings of any importance or size should have headings in the form of an arch. This is, however, the most inconvenient form we could choose, as respects the fitting of the valves of the doorway; for the arch-shaped head of the valves not only requires considerable nicety in fitting to the arch, but adds largely to the weight of the door,—a double disadvantage, straining the hinges and making it cumbersome in opening. And this inconvenience is so much perceived by the eye, that a door valve with a pointed head is always a disagreeable object. It becomes, therefore, a matter of true necessity so to arrange the doorway as to admit of its being fitted with rectangular valves.
II. Now, in determining the form of the aperture, we supposed the jamb of the door to be of the utmost height required for entrance. The extra height of the arch is unnecessary as an opening, the arch being required for its strength only, not for its elevation. There is, therefore, no reason why it should not be barred across by a horizontal lintel, into which the valves may be fitted, and the triangular or semicircular arched space above the lintel may then be permanently closed, as we choose, either with bars, or glass, or stone.
This is the form of all good doors, without exception, 184 over the whole world and in all ages, and no other can ever be invented.
III. In the simplest doors the cross lintel is of wood only, and glass or bars occupy the space above, a very frequent form in Venice. In more elaborate doors the cross lintel is of stone, and the filling sometimes of brick, sometimes of stone, very often a grand single stone being used to close the entire space: the space thus filled is called the Tympanum. In large doors the cross lintel is too long to bear the great incumbent weight of this stone filling without support; it is, therefore, carried by a pier in the centre; and two valves are used, fitted to the rectangular spaces on each side of the pier. In the most elaborate examples of this condition, each of these secondary doorways has an arch heading, a cross lintel, and a triangular filling or tympanum of its own, all subordinated to the main arch above.
IV. 2. Fillings of windows.
When windows are large, and to be filled with glass, the sheet of glass, however constructed, whether of large panes or small fragments, requires the support of bars of some kind, either of wood, metal, or stone. Wood is inapplicable on a large scale, owing to its destructibility; very fit for door-valves, which can be easily refitted, and in which weight would be an inconvenience, but very unfit for window-bars, which, if they decayed, might let the whole window be blown in before their decay was observed, and in which weight would be an advantage, as offering more resistance to the wind.
Iron is, however, fit for window-bars, and there seems no constructive reason why we should not have iron traceries, as well as iron pillars, iron churches, and iron steeples. But I have, in the “Seven Lamps,” given reasons for not considering such structures as architecture at all.
The window-bars must, therefore, be of stone, and of stone only.
V. The purpose of the window being always to let in as much light, and command as much view, as possible, these 185 bars of stone are to be made as slender and as few as they can be, consistently with their due strength.
Let it be required to support the breadth of glass, a, b, Fig. XLV. The tendency of the glass sustaining any force, as of wind from without, is to bend into an arch inwards, in the dotted line, and break in the centre. It is to be supported, therefore, by the bar put in its centre, c.
But this central bar, c, may not be enough, and the spaces a c, c b, may still need support. The next step will be to put two bars instead of one, and divide the window into three spaces as at d.
But this may still not be enough, and the window may need three bars. Now the greatest stress is always on the centre of the window. If the three bars are equal in strength, as at e, the central bar is either too slight for its work, or the lateral bars too thick for theirs. Therefore, we must slightly increase the thickness of the central bar, and diminish that of the lateral ones, so as to obtain the arrangement at f h. If the window enlarge farther, each of the spaces f g, g h, is treated as the original space a b, and we have the groups of bars k and l.
So that, whatever the shape of the window, whatever the direction and number of the bars, there are to be central or main bars; second bars subordinated to them; third bars subordinated to the second, and so on to the number required. This is called the subordination of tracery, a system delightful to the eye and mind, owing to its anatomical framing and unity, and to its expression of the laws of good government in all fragile and unstable things. All tracery, therefore, which is not subordinated, is barbarous, in so far as this part of its structure is concerned.
VI. The next question will be the direction of the bars. The reader will understand at once, without any laborious proof, that a given area of glass, supported by its edges, is stronger in its resistance to violence when it is arranged in a long strip or band than in a square; and that, therefore, glass is generally to be arranged, especially in windows on a large scale, in oblong areas: and if the bars so dividing it be placed horizontally, they will have less power of supporting themselves, and will need to be thicker in consequence, than if placed vertically. As far, therefore, as the form of the window permits, they are to be vertical.
VII. But even when so placed, they cannot be trusted to support themselves beyond a certain height, but will need cross bars to steady them. Cross bars of stone are, therefore, to be introduced at necessary intervals, not to divide the glass, but to support the upright stone bars. The glass is always to be divided longitudinally as far as possible, and the upright bars which divide it supported at proper intervals. However high the window, it is almost impossible that it should require more than two cross bars.
VIII. It may sometimes happen that when tall windows are placed very close to each other for the sake of more light, the masonry between them may stand in need, or at least be the better of, some additional support. The cross bars of the windows may then be thickened, in order to bond the intermediate piers more strongly together, and if this thickness appear ungainly, it may be modified by decoration.
IX. We have thus arrived at the idea of a vertical frame work of subordinated bars, supported by cross bars at the necessary intervals, and the only remaining question is the method of insertion into the aperture. Whatever its form, if we merely let the ends of the bars into the voussoirs of its heading, the least settlement of the masonry would distort the arch, or push up some of its voussoirs, or break the window bars, or push them aside. Evidently our object should be to connect the window bars among themselves, so framing them together that they may give the utmost possible degree of support 187 to the whole window head in case of any settlement. But we know how to do this already: our window bars are nothing but small shafts. Capital them; throw small arches across between the smaller bars, large arches over them between the larger bars, one comprehensive arch over the whole, or else a horizontal lintel, if the window have a flat head; and we have a complete system of mutual support, independent of the aperture head, and yet assisting to sustain it, if need be. But we want the spandrils of this arch system to be themselves as light, and to let as much light through them, as possible: and we know already how to pierce them (Chap. XII. VII.). We pierce them with circles; and we have, if the circles are small and the stonework strong, the traceries of Giotto and the Pisan school; if the circles are as large as possible and the bars slender, those which I have already figured and described as the only perfect traceries of the Northern Gothic.58 The varieties of their design arise partly from the different size of window and consequent number of bars; partly from the different heights of their pointed arches, as well as the various positions of the window head in relation to the roof, rendering one or another arrangement better for dividing the light, and partly from �sthetic and expressional requirements, which, within certain limits, may be allowed a very important influence: for the strength of the bars is ordinarily so much greater than is absolutely necessary, that some portion of it may be gracefully sacrificed to the attainment of variety in the plans of tracery—a variety which, even within its severest limits, is perfectly endless; more especially in the pointed arch, the proportion of the tracery being in the round arch necessarily more fixed.
X. The circular window furnishes an exception to the common law, that the bars shall be vertical through the greater part of their length: for if they were so, they could neither have secure perpendicular footing, nor secure heading, their thrust being perpendicular to the curve of the voussoirs 188 only in the centre of the window; therefore, a small circle, like the axle of a wheel, is put into the centre of the window, large enough to give footing to the necessary number of radiating bars; and the bars are arranged as spokes, being all of course properly capitaled and arch-headed. This is the best form of tracery for circular windows, naturally enough called wheel windows when so filled.
XI. Now, I wish the reader especially to observe that we have arrived at these forms of perfect Gothic tracery without the smallest reference to any practice of any school, or to any law of authority whatever. They are forms having essentially nothing whatever to do either with Goths or Greeks. They are eternal forms, based on laws of gravity and cohesion; and no better, nor any others so good, will ever be invented, so long as the present laws of gravity and cohesion subsist.
XII. It does not at all follow that this group of forms owes its origin to any such course of reasoning as that which has now led us to it. On the contrary, there is not the smallest doubt that tracery began, partly, in the grouping of windows together (subsequently enclosed within a large arch59), and partly in the fantastic penetrations of a single slab of stones under the arch, as the circle in Plate V. above. The perfect form seems to have been accidentally struck in passing from experiment on the one side, to affectation on the other; and it was so far from ever becoming systematised, that I am aware of no type of tracery for which a less decided preference is shown in the buildings in which it exists. The early pierced traceries are multitudinous and perfect in their kind,—the late Flamboyant, luxuriant in detail, and lavish in quantity,—but the perfect forms exist in comparatively few churches, generally in portions of the church only, and are always connected, and that closely, either with the massy forms out of which 189 they have emerged, or with the enervated types into which they are instantly to degenerate.
XIII. Nor indeed are we to look upon them as in all points superior to the more ancient examples. We have above conducted our reasoning entirely on the supposition that a single aperture is given, which it is the object to fill with glass, diminishing the power of the light as little as possible. But there are many cases, as in triforium and cloister lights, in which glazing is not required; in which, therefore, the bars, if there be any, must have some more important function than that of merely holding glass, and in which their actual use is to give steadiness and tone, as it were, to the arches and walls above and beside them; or to give the idea of protection to those who pass along the triforium, and of seclusion to those who walk in the cloister. Much thicker shafts, and more massy arches, may be properly employed in work of this kind; and many groups of such tracery will be found resolvable into true colonnades, with the arches in pairs, or in triple or quadruple groups, and with small rosettes pierced above them for light. All this is just as right in its place, as the glass tracery is in its own function, and often much more grand. But the same indulgence is not to be shown to the affectations which succeeded the developed forms. Of these there are three principal conditions: the Flamboyant of France, the Stump tracery of Germany, and the Perpendicular of England.
XIV. Of these the first arose, by the most delicate and natural transitions, out of the perfect school. It was an endeavor to introduce more grace into its lines, and more change into its combinations; and the �sthetic results are so beautiful, that for some time after the right road had been left, the aberration was more to be admired than regretted. The final conditions became fantastic and effeminate, but, in the country where they had been invented, never lost their peculiar grace until they were replaced by the Renaissance. The copies of the school in England and Italy have all its faults and none of its beauties; in France, whatever it lost in method or in majesty, it gained in fantasy: literally Flamboyant, it 190 breathed away its strength into the air; but there is not more difference between the commonest doggrel that ever broke prose into unintelligibility, and the burning mystery of Coleridge, or spirituality of Elizabeth Barrett, than there is between the dissolute dulness of English Flamboyant, and the flaming undulations of the wreathed lines of delicate stone, that confuse themselves with the clouds of every morning sky that brightens above the valley of the Seine.
XV. The second group of traceries, the intersectional or German group, may be considered as including the entire range of the absurd forms which were invented in order to display dexterity in stone-cutting and ingenuity in construction. They express the peculiar character of the German mind, which cuts the frame of every truth joint from joint, in order to prove the edge of its instruments; and, in all cases, prefers a new or a strange thought to a good one, and a subtle thought to a useful one. The point and value of the German tracery consists principally in turning the features of good traceries upside down, and cutting them in two where they are properly continuous. To destroy at once foundation and membership, and suspend everything in the air, keeping out of sight, as far as possible, the evidences of a beginning and the probabilities of an end, are the main objects of German architecture, as of modern German divinity.
XVI. This school has, however, at least the merit of ingenuity. Not so the English Perpendicular, though a very curious school also in its way. In the course of the reasoning which led us to the determination of the perfect Gothic tracery, we were induced successively to reject certain methods of arrangement as weak, dangerous, or disagreeable. Collect all these together, and practise them at once, and you have the English Perpendicular.
As thus. You find, in the first place (V.), that your tracery bars are to be subordinated, less to greater; so you take a group of, suppose, eight, which you make all exactly equal, giving you nine equal spaces in the window, as at A, Fig. XLVI. You found, in the second place (VII.), that there was 191 no occasion for more than two cross bars; so you take at least four or five (also represented at A, Fig. XLVI.), also carefully equalised, and set at equal spaces. You found, in the third place (VIII.), that these bars were to be strengthened, in order to support the main piers; you will therefore cut the ends off the uppermost, and the fourth into three pieces (as also at A). In the fourth place, you found (IX.) that you were never to run a vertical bar into the arch head; so you run them all into it (as at B, Fig. XLVI.); and this last arrangement will be useful in two ways, for it will not only expose both the bars and the archivolt to an apparent probability of every species of dislocation at any moment, but it will provide you with two pleasing interstices at the flanks, in the shape of carving-knives, a, b, which, by throwing across the curves c, d, you may easily multiply into four; and these, as you can put nothing into their sharp tops, will afford you a more than usually rational excuse for a little bit of Germanism, in filling them with arches upside down, e, f. You will now have left at your disposal two and forty similar interstices, which, for the sake of variety, you will proceed to fill with two and forty similar 192 arches: and, as you were told that the moment a bar received an arch heading, it was to be treated as a shaft and capitalled, you will take care to give your bars no capitals nor bases, but to run bars, foliations and all, well into each other after the fashion of cast-iron, as at C. You have still two triangular spaces occurring in an important part of your window, g g, which, as they are very conspicuous, and you cannot make them uglier than they are, you will do wisely to let alone;—and you will now have the west window of the cathedral of Winchester, a very perfect example of English Perpendicular. Nor do I think that you can, on the whole, better the arrangement, unless, perhaps, by adding buttresses to some of the bars, as is done in the cathedral at Gloucester; these buttresses having the double advantage of darkening the window when seen from within, and suggesting, when it is seen from without, the idea of its being divided by two stout party walls, with a heavy thrust against the glass.
XVII. Thus far we have considered the plan of the tracery only: we have lastly to note the conditions under which the glass is to be attached to the bars; and the sections of the bars themselves.
These bars we have seen, in the perfect form, are to become shafts; but, supposing the object to be the admission of as much light as possible, it is clear that the thickness of the bar ought to be chiefly in the depth of the window, and that by increasing the depth of the bar we may diminish its breadth: clearly, therefore, we should employ the double group of shafts, b, of Fig. XIV., setting it edgeways in the window: but as the glass would then come between the two shafts, we must add a member into which it is to be fitted, as at a, Fig. XLVII., and uniting these three members together in the simplest way, with a curved instead of a sharp recess behind the shafts, we have the section b, the perfect, but simplest type of the main tracery bars in good Gothic. In triforium and cloister tracery, which has no glass to hold, the central member is omitted, and we have either the 193 pure double shaft, always the most graceful, or a single and more massy shaft, which is the simpler and more usual form.
XVIII. Finally: there is an intermediate arrangement between the glazed and the open tracery, that of the domestic traceries of Venice. Peculiar conditions, hereafter to be described, require the shafts of these traceries to become the main vertical supports of the floors and walls. Their thickness is therefore enormous; and yet free egress is required between them (into balconies) which is obtained by doors in their lattice glazing. To prevent the inconvenience and ugliness of driving the hinges and fastenings of them into the shafts, and having the play of the doors in the intervals, the entire glazing is thrown behind the pillars, and attached to their abaci and bases with iron. It is thus securely sustained by their massy bulk, and leaves their symmetry and shade undisturbed.
XIX. The depth at which the glass should be placed, in windows without traceries, will generally be fixed by the forms of their bevelling, the glass occupying the narrowest interval; but when its position is not thus fixed, as in many London houses, it is to be remembered that the deeper the glass is set (the wall being of given thickness), the more light will enter, and the clearer the prospect will be to a person sitting quietly in the centre of the room; on the contrary, the farther out the glass is set, the more convenient the window will be for a person rising and looking out of it. The one, therefore, is an arrangement for the idle and curious, who care only about what is going on upon the earth: the other for those who are willing to remain at rest, so that they have free admission of the light of Heaven. This might be noted as a curious expressional reason for the necessity (of which no man of ordinary feeling would doubt for a moment) of a deep recess in the window, on the outside, to all good or architectural effect: still, as there is no reason why people should be made idle by having it in their power to look out of window, and as the slight increase of light or clearness of view in the centre of a room is more than balanced by the loss of space, and the 194 greater chill of the nearer glass and outside air, we can, I fear, allege no other structural reason for the picturesque external recess, than the expediency of a certain degree of protection, for the glass, from the brightest glare of sunshine, and heaviest rush of rain.
58 “Seven Lamps,” p. 53.
59 On the north side of the nave of the cathedral of Lyons, there is an early French window, presenting one of the usual groups of foliated arches and circles, left, as it were, loose, without any enclosing curve. The effect is very painful. This remarkable window is associated with others of the common form.