Part 16

Having secured the first object--an arch of reduced pressure--the second, viz., the abutment of an increased resistance, was attained by the systematic development of the buttress--a feature very much neglected by the Romanesque builders; and, as the vaulting of a lofty nave could not be directly supported by the ordinary buttress, the arched or flying buttress was introduced, spanning the aisles and conveying the pressure to the buttresses beyond. That this was introduced for utility only, and not from taste, is proved by the attempts in early instances to conceal it; so that we may with certainty conclude that all these beautiful features of Gothic architecture originated not from taste or caprice, but from reasoning upon practical and urgently pressing constructional requirements, and that the beauties to which they gave rise proceeded from the application to them of the great principle of Gothic architecture, the decoration of constructive or useful features.

Let us, however, suppose for a moment that our building is not vaulted, but has timber roofs; there still remains an advantage in the use of the pointed arch. If it has, for instance, a central tower, the demand for an arch of reduced thrust is still greater than if the church had been vaulted, for the arms of the cross, from their reduced weight, are less effective as abutments.

The chancel arch, again, demands height, and the more so if it be wide, as in our own day is necessary. The nave arcades are better pointed than round, as are any others carrying any considerable weight. Buttresses remain necessary at the ends of the arcades, and are desirable as a steadiment to the outer walls, particularly where roofs without a direct tie are made use of, and are further useful as permitting the introduction of larger windows than might be safe without them. In all cases, indeed, where roofs or floors are so constructed as to concentrate pressure upon points, it is clear that buttresses are desirable; and when the efficient size cannot be given them without inconvenience or dissight, it is equally clear that the deficiency may be readily compensated by loading them with lofty pinnacles. It is wrong to use buttresses without any object but appearance, but there are numbers of cases where they are of great advantage, besides those in which we know them to be indispensable. If so many of our arched and vaulted buildings in these days were not mere pretences in lath and plaster, we should have more practical experience of the need of the buttress and of the pointed arch. I was once told by the English Commissioner in Scinde that the European engineers had difficulty in making the native builders there believe that any but a pointed arch will stand.

Let us now inquire as briefly as may be into the _rationale_ of _ribbed_ vaulting as distinguished from the _arris_ vaulting of the Roman and earlier Romanesque builders.

A groined vault does not of absolute necessity demand the use of ribs any more than the plain waggon-head vault. Even the latter was from an early period frequently divided into compartments or bays by transverse ribs, which were useful as a means of giving it rigidity; but in _groined_ vaulting these were of nearly constant use, both for the same reason, and because the vault, being reduced at its springing to so narrow a footing, required this additional strength. The arrises, however, or diagonal lines of intersection, were always left without ribs.

Why, then, was the custom changed? For two important reasons. The first was this: that the intersection forms naturally a feeble line, both from the difficulty, particularly with the rough materials usually employed, of making its construction sound; from its forming an arch of greatly increased width without corresponding increase of height: and from its reduction at the springing level to a pin’s point.

The second was of a more intricate nature, and requires to be explained more in detail. When the two intersecting vaults of a groin are similar and equal in their section, or when the section of one is the mathematical resultant of that of the other, the line of intersection falls in a _plane_. When vaulting, however, became general, all sorts of irregularly-formed spaces would have to be so covered, and would present problems of considerable difficulty, in which it would be impossible in all cases that the vaulting surfaces should be portions of cylinders or regular cylindroids, and in which the intersecting lines could not, without much twisting of the surfaces, be brought to fall into planes.

The introduction of the diagonal rib met both of these difficulties. It strengthened the weak angle and gave it a substantial footing; and it at the same time gave to the lines of intersection a certain degree of independence of the vaulting surfaces; so that, instead of the surfaces governing the intersection, they were thenceforth governed by the ribs, and the latter could be made to fall into planes, and to avoid unsightly forms even in vaulting spaces of the most irregular and abnormal forms.

The substitution of the rib for the arris worked as great a revolution in the principles of vaulted construction as did the pointed arch itself. Nothing in the way of vaulting was now impracticable or unsightly; the architect was absolutely master of his work, and could do what he liked with it. The facilities it offers are quite marvellous in the eyes of the modern practical man when once they are opened to them. I have myself found one of the most practical men I ever met with, who had for years taken the leading management of the business of the greatest builder of our day, though hitherto uninitiated in Gothic construction, almost in ecstasies at finding a difficult problem in vaulting he had been puzzled over for days and making models of in vain, solved in an instant by seeing the absolute liberty of action exercised in a similar case in Westminster Abbey. The old builders themselves perfectly luxuriated in their newly-discovered liberty: not only could they vault spaces of any conceivable plan, every dimension of it varying, and the difficulties increased by the necessity of pushing up windows in its sides in all kinds of difficult positions, but they could make the result so pleasing and apparently so straightforward and natural, that not one observer out of a thousand ever finds out that there was any difficulty to be got over at all. Sometimes, indeed, we find them rejoicing so much in their freedom as to set themselves needless puzzles for the very luxury of solving them. There is a most remarkable instance of this in the crypt under Glasgow Cathedral, where the pillars which support the floor have been placed in a variety of intricate positions for no reason, apparently, but to produce curious perplexities in the vaulting and create strange problems, for the mere pleasure to be derived from their solution and the beauty of the puzzle when solved.[59]

It has been argued that the Gothic vault is less refined than some of the previous forms, because less strictly mathematical; that a refined system of construction should in all cases possess an exact mathematical solution, though the builder may, when once master of the true theory, depart from it in execution; that the work, in short, though irregular in execution, should be perfect and mathematically accurate in its theoretical type.

I agree with this doctrine in the main; but I hold that the Gothic vault complies with its conditions.

The square groined vault, with semicircular arches, is perfect in its theory, and gives elliptical arches for its arris lines. The same, if vaulted with the pointed arch, is equally true in theory, for the diagonal ribs may be pointed arches, formed each of portions of two ellipses. The oblong vault, again, is perfect if the wide arch is a semicircle, the narrow one a vertical semi-ellipse, and the arrises horizontal semi-ellipses of the same height; but the ancients generally chose to stilt the narrow arch instead of using the vertical ellipse, and by doing so threw the diagonal arris out of the plane and out of shape; but the theoretical form remained, nevertheless, perfect. In like manner, if the same figure be vaulted across its widest span by a pointed vault, and if the narrow vault have a pointed arch composed of two portions of ellipses, and the intersections be of the same figure as resulting geometrically from the intersection of the two vaults, the theoretical form is perfect. Now, if in either case the architect thinks the elliptical pointed arches inferior in beauty to those composed of parts of circles, and by using ribs finds himself enabled to throw the error resulting from the substitution of the latter form into the vaulted surfaces where it will be invisible, surely he is only using that discretionary power of introducing irregularities upon a perfect theory which is claimed as his right; and this is exactly what the Gothic architects introduced.

The fact is that, besides its unpleasing form, especially when the major axis is vertical, the use of the ellipse entails such an annoying series of difficulties as greatly to increase the trouble and consequent cost of execution. The constant change of curvature, the troublesome methods of striking it, and of finding the true lines of the arch-joints, not to mention the mathematical fact that the same joint line is never true both for the extrados and intrados, and that, if the rib-mould remains unchanged in depth, the extrados and intrados cannot be both true ellipses at all; all these furnish quite sufficient practical reasons for its rejection in cases where not only is there no necessity but an abstract mathematical idea to be satisfied by its use, but the beauty of the work is greatly improved by dispensing with it.

Though the pointed arch was introduced from purely constructive reasons, there was another of a more æsthetical nature, which rendered its adoption more general when once introduced. It was a double one; not only did the general tendency towards lofty proportions render it necessary to make use of an arch more in harmony with the general feeling of the architecture, but the rejection of a fixed code of proportions for pillars and other parts demanded for the arch an equal power of varying its own proportions. The semicircular arch is absolute and invariable, and though the use of smaller segments would meet the case in one direction, there were no means of proportioning it to features of _increasing_ height. This was attempted both in Romanesque and Byzantine works by the expedient of _stilting_, but this is, after all, more a semblance than a reality. As in cases already cited, the mathematical solution of the problem is the ellipse; but only imagine anything so unpleasing as a series of elliptical arches placed the length-way upwards! Good taste would not suffer it. But the pointed arch at once met the difficulty. To illustrate my meaning, I will beg you to take an internal bay of a Norman cathedral (Fig. 146), and to suppose yourselves to have to increase its height throughout in the ratio of one-third (Fig. 147).

You first, after setting out your widths as in the original, increase the whole height and that of each storey by one-third; you then increase the pillars and the jambs of the triforium and clerestory windows in the same proportion: this brings you to a stand, for the arches, being semicircles, are invariable. Either you must leave them unaltered and throw all the extra height into the wall above them, or you must stilt them each to the extent of one-third of their height unless you can make use of an elastic arch which will change its proportion at pleasure. The ellipse occurs and meets the case, but it offends your eye. At length, however, the pointed arch suggests itself, and gets rid of the whole difficulty. So similar are a Romanesque and an Early Pointed bay in all other respects, that the change of proportion which I have described seems at once to effect the whole change in style.

Had the constructional motive alone existed, the pointed form would have been confined to arches of considerable span; but the demand for a variable arch adding æsthetic to the constructional claim, caused its speedy adoption in positions where strength alone would not have demanded it, though the semicircle, the plain segment, and the segmental pointed arch, were, at all subsequent periods of the style, used side by side with the true pointed form.

I have been the more particular in showing the true reasons for the change in the form of the arch, because the great majority of writers treat it purely as a matter of taste and of altered fashion; indeed, some excellent writers on the history of Mediæval architecture have strangely imagined that the pointed arch had a greater outward thrust than the round, and that the increased projection of the buttresses was necessitated by its use, instead of the two being simultaneously introduced as a double means of avoiding the evils experienced from the great thrust of the round arch and the small buttresses by which it had, during the Romanesque period, been accompanied.

I will now close my present lecture, but hope in the next to carry on the same inquiry into a number of other details, as well as into the general spirit and principles of the architecture of which I am treating, and to add some practical remarks on the application of the _rationale_ thus traced out to our present revival of the style, and such developments as it may give rise to.

LECTURE VII.

The Rationale of Gothic Architecture--_Continued_.

The bases of a thirteenth century church indicate the plan and construction of the vaulting--The system of mouldings--Windows, their development--Rationale of stained glass--A general principle of ornamentation common to all good architecture--The roof--Secular buildings--Cloth market Yprès--Warehouses, Nuremburg--Windows in secular and ecclesiastical buildings--Trabeated architecture in its truest forms--Fireplaces--Chimney-shafts--Oriel and Dormer windows--Ceilings--Subordination of external design to internal requirements--Designs adapted to the materials most readily obtained--Conditions demanded of our future architecture--Gothic architecture well fitted to unite these conditions.

In my last lecture I traced out the _rationale_ of a number of the leading features, both of Romanesque as distinguished from Roman architecture, and subsequently of Gothic as distinguished from Romanesque. I will endeavour to avoid wearying you by carrying the inquiry into too great a multiplicity of details, but I must, nevertheless, ask your indulgence while I pursue them somewhat further than I have yet done.

Nothing would, perhaps, do more to show the reasonableness of the various developments in question than to trace out the details of the vaulting system; to show the varieties it exhibited in different countries and provinces and at different periods, the various modes adopted for effecting a given purpose and the many mechanical and other difficulties to be contended with, and the methods adopted of meeting them. This is, however, so extensive and so intricate a subject, that, if I had devoted these two lectures exclusively to it, I could barely have done it justice. I will, therefore, at present content myself with referring those of you who are anxious to make yourselves acquainted with it, to an admirable and elaborate essay on the subject by Professor Willis, in the Transactions of the Institute of British Architects, and to the article “Construction,” in the fourth volume of Viollet le Duc’s Dictionary. No one who has not gone carefully and practically into the subject can have any idea of the amount of forethought which it demands; so much so that, as Viollet le Duc says, the design for a vaulted building has to be commenced at the top and worked downwards; and we may often form a pretty correct idea, from the bases of a thirteenth century church, of what was the plan and construction of its vaulting.

This principle of designing each part from the first with reference to its ultimate intention is very strongly marked in French works of the twelfth and thirteenth centuries, and in those of the transitional period in England. The form, not only of the capital, but even of the base of each shaft, usually indicates the direction of the arched rib or order which it is destined to carry.

This was, however, lost in English works on the introduction of the circular abacus, and I must say that much expression and emphasis was lost with it. Not only, indeed, did the abacus in French work face or point in the direction of the arched rib, but its plan was often made to fit to it in the most direct manner, and even the direction of the principal stalks of the foliage had reference to the supported rib (Fig. 148).

The system of moulding, again, follows out the same laws of reason. An arch-moulding, for instance, is founded on what is supposed to be the original section of the order or rib. Thus, if the normal section of the rib be square, the section of the mouldings is made to fit to that figure (Fig. 149); if chamfered or a part of an octagon, the mouldings, again, fit to it (Fig. 150); the abacus in each case taking the normal plan of the ribs.

As to æsthetical forms, the mouldings were studiously arranged so as to produce in some parts the greatest contrasts, in others the most elegant gradations of light and shade. The heaviness of large roll mouldings was often relieved by fillets or by raised edges or “keels,” by which diversity was gained without loss of mass (Fig. 151).

Hollows, again, were relieved by the insertion of sparkling ornaments, such as the toothed ornament, the rosette, the ball-flower, the four-leaved flower, and many others; and in other instances by the introduction of bands of foliage. The sections of moulding differed entirely from those of Roman architecture, being far more free and less mechanical, and at once more delicate in feeling and more carefully studied with reference to light and shade. They resembled Greek mouldings, in fact, far more than Roman.

Enriched mouldings differed from the usual practice in antique work in this respect, that the enrichment was added to instead of being cut out of the original moulding; its practical use being to strengthen the hollows rather then to enrich the rounds. In this respect the practice of the Romanesque builder had been different; and perhaps a union of the two systems would be better than a close adherence to either.

Mouldings which receive much rain, as copings, cills, tops of cornices etc., were very much more sloped than in Classic work, so as to throw off the wet more rapidly. The custom in modern Classic buildings, where the stone is not very hard, of putting lead on the upper surface, as well as the damage often sustained when this is neglected, show the reasonableness of this increased slope. They had to do with a more rainy climate, and generally with softer stone, than the ancients, and they designed their work accordingly. The under sides, again, of projecting mouldings, as string-courses, drip-stones, water-tables, cills, etc., were carefully designed so as to prevent the wet from running round them. Base mouldings round buildings were designed in such a manner as both really and apparently to give it a substantial footing, and at the same time to add greatly to its beauty; many of them are as noble combinations as could easily be conceived.[60]

In short, it may be asserted, without fear of contradiction, that in no style of architecture has a system of moulding been generated so full of variety and so capable of suiting itself to every position; and not only to provide for the practical demands of each position, but to give to each just that kind of effect which it most demanded.

Let us now proceed to consider the _window_. In the days of ancient Greece, and in the earlier days of Rome, windows were necessarily kept in a very undeveloped form, through the non-existence of window glass; so much so, that in Classic architecture the window seems a thing shunned as an unhappy necessity; and the imperfect manufacture and dearness of this material, no doubt, influenced, in a considerable degree, the architecture of the later Roman and the immediately succeeding periods. In churches and other vaulted buildings, another cause would lead to the use, during the last-named (_i.e._, the Romanesque) period, of as small windows as would just answer the purpose. The unaided thickness and the whole length of the wall being relied on for the abutment of the vaulting, it naturally followed that perforations were as much avoided as possible, as tending to reduce the abutting mass. Accordingly, as buttresses increased in projection, greater and greater openings in the curtain wall were ventured on, simply because there was strength sufficient to admit of them, till, when Pointed architecture received its full development, and the pressure of the vaults was entirely concentrated upon the buttresses, the whole intervening space might, if needful, be converted into windows.

Simultaneously with this change, the increasing use of stained glass _necessitated_ a corresponding increase in the area of window opening, so that we have one development _facilitating_, and the other _rendering necessary_, the constant enlargement and multiplication of the windows.

The _primâ facie_ mode of obtaining increased window light would be by widening the openings; but as this, if carried too far, would at once injure the beauty of the window and cause inconvenience in glazing it, the more usual course adopted was to increase the number. Hence the couplets, triplets, and more numerous groups of the Early English windows. These groups, when placed in a side wall and under a level roof-plate, would naturally assume the form of arcades of equal height; but when under a gable, an arched roof, or a vaulted bay, they increased in height towards the centre,--thus giving us the two most familiar forms of grouping. The sections of the jambs were arranged (as in the earlier period) in the manner best suited to the admission of light--care being taken externally to avoid deep shadows upon the glass, and internally, to disperse the light as readily as possible through the building.

In domestic buildings, where windows have to serve the double purpose of admitting the light and facilitating external view, they were not usually grouped as above described, but were made wider in their openings, the unpleasant effect which might otherwise arise from it being obviated, and the glazing and opening of the window rendered more easy by the use of thin mullions or pillars dividing the window into two or more lights. This system offered advantages so obvious that it was very soon adopted for churches also; so that, instead of obtaining increased light, as heretofore, by the indefinite multiplication of comparatively small windows, it became customary now, _for the first time in the history of architecture_, to make windows of _any_ size which their position or utility might dictate; the whole end of a church and the entire bays of its flanks being occupied, if need be, by single windows.