During the Romanesque period, or roughly speaking, from the beginning of the eleventh to the middle of the twelfth century, three chief forms of vaulting were employed over the naves and aisles of church edifices. The first of these was the dome, the second the tunnel vault, and the third, groined vaulting. With the development of the ribbed vault, all three gave way to this new method of construction, and the Gothic era was inaugurated. Domes on Spherical Pendentives The dome was employed in two rather distinct ways according to the form of pendentives used for its support. Thus a number of churches continue the tradition of the spherical pendentive, while in others some form of squinch or trumpet arch is found. Both methods are of early origin, dating back, in fact, to the Roman era preceding the reign of Justinian (483-565) and consequently earlier than the Byzantine architecture of which they are so conspicuous a feature. Rivoira[1] has shown the existence of numerous spherical pendentives of the second century A.D. or even earlier, and Lasteyrie[2] has added to these a small cupola at Beurey-Beauguay (CÔte-d’Or) in France dating from the second or third century. But even if this method were known at an early date it was not until the Byzantine era that it obtained a wide-spread and extensive usage. During the sixth century it became the principal method of vaulting throughout the Roman Empire, and, as such, had a considerable influence upon Carolingian architecture of the ninth and tenth centuries. This is true even in France, for traces of pendentives were found in 1870 during a restoration of the church of Germigny-des-PrÉs,[3] a fact of particular interest because it is in France that the principal Romanesque examples of this method are to be seen. Domes on Squinches As for the squinch, it may possibly be of Persian origin, but the earliest examples thus far known in Persia are to be found in the palaces of Firouz Abad and Sarvistan, which probably date from the Sassanian period between A.D. 226 and 641, and are therefore of later date than the Roman examples of the first and second centuries to be found in the Palace of the Caesars at Rome and the Villa Adriana at Tivoli (cir. A.D. 138). Whatever its origin, the squinch in its various forms, simple cross lintel,[4] cross arch, trumpet arch, niche head, etc., was employed prior to and during the Byzantine period along with the spherical pendentive. In fact a trumpet arch of domed up character is found in the Baptistery of the cathedral of Naples[5] which dates from the fifth century, while the niche head or half dome type, very commonly employed in Romanesque architecture, has a sixth century prototype in the church of San Vitale at Ravenna,[6] as well as many earlier examples such as those in the Domus Augustana (cir. A.D. 83),[7] or the Thermae of Caracalla (212-216)[8] at Rome. Other types of squinches occasionally appear but they are generally referable to one of the above mentioned forms. The School of Perigord By far the most important group of Romanesque churches employing the dome on spherical pendentives, is situated in that portion of France extending around the city of PÉrigueux, and constitutes what is known as the architectural school of Perigord. Since PÉrigueux was a trading post on the route from Venice to the west, it must have felt a good deal of Byzantine influence, and it is the general theory that to this influence is due the almost universal employment of the dome on pendentives in the churches of this school. While this may well be the case, it is nevertheless to be remarked that the dome as a method of vaulting seems to have been the only importation, its construction in Perigord differing in almost every particular from that of the Byzantine period. This might even seem to indicate that the Perigord type of dome was not imported, but actually indigenous to this part of France, a theory which has lately been advanced by no less an authority than Lasteyrie.[9] But in any case, the points of difference in construction between the domes of Byzantine architecture and those of the school of Perigord are of more importance in this discussion of vaulting, than is the question of their origin. Comparison of Perigord and Byzantine Domes
These differences have been so admirably summed up by Lasteyrie[10] that a translation of his summary with a few additions will perhaps give the best possible account of them. They are grouped under six chief heads which may all be studied by using the cathedral of Saint Front at PÉrigueux (Figs. 1 and 2) as a model. First, the French pendentives are borne on pointed instead of semicircular arches; second, the surface of the pendentive at Saint Front rises from the intrados rather than from the extrados of the voussoirs; third, the diagonal profile of the French pendentive is a complex curve[11] instead of a quarter circle; fourth, the oldest French pendentives have their masonry in horizontal courses while the Byzantine frequently have their courses more or less normal to the curve; fifth the springing of the domes of Saint Front is some distance back from the circle formed by the pendentives, the diameter of the dome being thus greater than its impost,[12] while in Byzantine models, the two correspond; and sixth and last, the domes of Saint Front are slightly pointed and, for that matter, all the French domes are at least semicircular, while the Byzantine domes are generally of segmental section. The explanation of all these differences lies in the material employed, for the domes of Perigord are of stone, those of Byzantine architecture are of brick or some other light material. The pointed arch having less thrust than that of semicircular section was better suited for stone construction, a fact which explains the pointed section of many French domes whose outward thrusts were thereby greatly reduced. Moreover, while the light Byzantine material made possible a dome without centering constructed after the manner of the Egyptian “voute-par-tranches,”[13] the heavy stone of the French vault made a centering absolutely necessary, a fact which explains the setting back of the dome from the curve of the pendentives so that the ledge thus formed might serve to support the wooden centering employed.[14] It explains also the horizontal courses since these allowed a greater amount of the weight of each course to be borne by the one beneath it, thus reducing the pressure and making possible a centering of comparative lightness. But these were not the only results of the employment of stone. Since the domes of Perigord are much heavier than the Byzantine domes and exert much more outward thrust it was essential for them to have very firm supports. Perhaps it is with this in view that the churches of this school are for the greater part without side aisles, their outer walls with heavy applied and transverse arches providing suitable support for the domes. Even when aisles exist, they are merely deep wall arches forming transverse tunnel vaults rising from the level of the imposts of the transverse arches of the nave and, with them, furnishing the support for the triangular pendentives. This is the arrangement in the cathedral of Saint Front at PÉrigueux (Fig. 1), the only church in France of this particular type.[15] The Exterior Roofing of Perigord Domes One advantage in the employment of the dome of stone lay in the fact that it might be faced on both the exterior and the interior, or covered directly by tiles without the use of a bonnet of wood and copper, or a roof of wood and tile, so frequently seen in Byzantine work. It is doubtful whether the earliest French domes were treated in this way, however, for indications would seem to point to the original employment of a wooden roof over the domes of the cathedral of Saint Front.[16] Nevertheless, these domes have since been restored with an exterior stone facing (Fig. 2), and a similar treatment is to be seen at Cahors cathedral, and over the crossing of AngoulÊme. In these domes the drum is first built up in a slightly ramping wall, to offset the outward thrust of the vault, and the dome itself is crowned by a lantern toward which it has an upward curve, rendering the exterior steep enough to shed water readily. At AngoulÊme the domes of the nave are entirely concealed by a gable roof, perhaps in the early manner of the school. Still another type of dome covering appears at Saint Étienne in PÉrigueux,[17] where the curve of the dome does not show on the exterior, but where the drum is first carried up around the haunch, and then surmounted by a flattened conical roof of tile, which rests directly upon the vault beneath. Characteristics of Perigord Churches It has already been noted that the employment of the dome on pendentives over square bays led to the construction of churches with a broad nave without side aisles. Among the earliest of these are the church of Saint Astier (Dordogne), (founded about 1010 but so mutilated as to show little of its original construction),[18] and Saint Avit-SÉnieur (Dordogne) (cir. 1117), originally with three domes which were replaced by domed up Anjou vaults in the thirteenth century.[19] The best of the earlier examples remaining for critical study are, first, the cathedral of Saint Pierre at AngoulÊme, whose western bay was constructed between 1100-1125,—the remaining three being but slightly later—and second, the church of Saint Étienne at PÉrigueux, originally with four domes, two of which were destroyed in the religious wars of the sixteenth century. Of the two which remain the more recent must be earlier than 1163, and the other would seem from its appearance to be about contemporary with that of the west bay of AngoulÊme.[20] These two with the cathedral of Saint Front (after 1120) furnish three excellent examples of the school, to which a large number of other churches might be added as illustrating some minor differences in plan or elevation.[21] The cathedral of AngoulÊme (Figs. 3 and 4) is characteristic of the school. Deep wall, and heavy transverse arches supply substantial impost for the domes. The piers of the western bay are of simple rectangular plan like those of Saint Avit-SÉnieur and Saint Étienne at PÉrigueux, while those to the east are of a later compound type with transverse arches and wall-arches in two orders instead of the single order of the earlier bay. Except over the crossing, where there is a high circular drum forming a lantern, the domes are not pierced with windows around their base. This is due to the fact that they are covered on the exterior by a wooden roof.[22] It is more usual to find four small windows at the base of each dome as in PÉrigueux, Saint Front (Fig. 1).[23] The use of stone in the construction of the domes explains the small number of these windows compared to that in Byzantine architecture,[24] since the stability of the vault would be threatened by too many openings. Besides this, the fact that the churches of Perigord have no aisles, properly speaking, permitted sufficient light to enter through windows in the side walls. In fact it seems quite possible that the windows in the domes of the Perigord churches were used to afford resting places for the frame work of the centering even more than for light, a fact which would also seem to be true of the four recesses left in the masonry just above the cornice of the domes of AngoulÊme cathedral (Fig. 4). The Centering of Perigord Domes In support of this theory it is possible to point out that if long cross beams were used in building these domes, it would be difficult if not impossible to remove them after the dome was finished. If, however, as at AngoulÊme, small spaces were left in the masonry it would be possible to tilt a beam bevelled at each end and resting on the ledge of the dome and thus remove it without cutting. Still another argument in favor of this theory is the fact that the open spaces to north and south are above the level of the ledge, which would seem to indicate that they were planned to receive the end of a cross beam at right angles to, and above the one running lengthwise. Of course, when windows took the place of these small recesses the removal of the beam could be made through them. There remain, however, a number of churches in which there are neither windows nor recesses, but in most of these the ledge of the dome is itself wide enough to support a beam which could be removed without striking the vault surface. Fig. 4.—AngoulÊme, Cathedral. As for the choirs of the churches of this school, they were occasionally domed as at Saint Front[25] (Fig. 1), but were more often covered by a tunnel vault terminating in the half dome of the apse. The eastern portion of the choir of Saint Front (Fig. 1) and the choir of AngoulÊme (Fig. 4) illustrate this latter arrangement. Naves Vaulted with Domes on Squinches Although very frequently used over the crossing of Romanesque churches, the dome on squinches is seldom found over the bays of the nave. There is in fact no distinct school in which this method is employed and the examples of its use are widely scattered. The principal one is, perhaps, the cathedral of Notre Dame at Le Puy (Haute-Loire), which dates from the eleventh and twelfth centuries. Unlike the domed churches of Perigord it is of basilical plan with side aisles. The nave is in six bays with broad arches opening into the aisles and a triforium arcade above them. Across the nave are transverse arches separating the bays. The four toward the east are semicircular, the remaining two are pointed in elevation. These arches rise from imposts nearly or quite as low as those of the nave arcade, and walls are built upon them to the level of the string-course above the triforium. Six rectangular bays,—or seven including the crossing,—of practically square plan are thus formed and each is covered with a dome. In the western bays,—which are at least a century later than those at the east end and therefore more advanced in structure,—a clerestory wall is erected with a single window in its north and south walls, and openings corresponding to windows from one bay to the next above the transverse arches, to secure a good distribution of light (Fig. 5). Across the upper corners of these four walls and rising from the same level as the window heads, are arches with half domed triangular niches beneath them, converting the square into an octagon and furnishing the impost for the domes.[26] These are octagonal in elevation as well as plan and are laid up in flat panels, or gores, which meet at the crown (Fig. 6). It is a type of dome admirably suited to its impost since it presents none of the awkward appearances of a circular dome on an octagonal base.[27] It is also very practical from a structural standpoint. Since the gores are flat, the stone cutting is far less elaborate than in a hemispherical dome, and the gored dome has the further advantage of great flexibility since it may be flattened or raised at the crown, placed over a square bay or one with any number of sides, and made equilateral or with gores of different widths, all with great facility. Furthermore, when the naves are of reasonable width, as in most churches with side aisles, the thrust of the dome is very slight and its downward pressure is not excessive.
But with all its structural advantages, a system like that at Le Puy was not a satisfactory solution of nave vaulting. The transverse arches were necessarily so far below the surface of the dome that the continuity of the nave as a whole was destroyed, and the appearance was rather that of a series of lantern towers or crossings juxtaposed than of a single homogeneous vault. The side aisles of Le Puy are of less importance than the nave, though the fact that some of their bays were vaulted, or revaulted, at nearly every period of mediaeval architecture makes them interesting for a study of consecutive methods. In the bays to the east the vaults are groined on stilted, round headed transverse arches in the early Romanesque manner, while the succeeding bays have pointed transverse arches with groined vaults closely resembling those of the school of Bourgogne, and the bays nearest the west end have ribbed vaults, in one case with the early heavy-torus rib, in another with the light rib of pointed section of a late Gothic rebuilding. Although not the basis of a school of Romanesque architecture, the cathedral of Le Puy was not without its influence. This is especially apparent in the large church of Saint Hilaire at Poitiers (Figs. 7, and 8), which was constructed with very broad nave and aisles,—both covered with wooden roofs,—after a disastrous fire of 1018, and dedicated in 1059. In 1130 the vaulting of this church was undertaken, the result being a most unusual edifice. As the nave was too broad to be easily covered by a vault of single span, it was subdivided by lofty and slender piers and arches into a central portion consisting of square bays,[28] and narrow rectangular bays forming veritable inner aisles on either side. These narrow bays were covered with groined vaults directly above the original clerestory windows which thus continued to light the newly formed nave. Domes were then placed over the square central bays as had been done at Le Puy, but instead of the niche-head-squinch and the practically equilateral octagonal dome, small conical trumpet arches were employed at Saint Hilaire, and the gores of the dome rising from these were much narrower than the four remaining panels. This gives the dome rather the character of a cloistered vault with its corners cut off than of a dome properly speaking. Since the clerestory is below the level of the transverse arches upon which the domes of Saint Hilaire are built, the interior has a loftier and less broken appearance than that of Notre Dame-du-Puy. But even so the effect is not remarkably pleasing. The side aisles of Saint Hilaire (Fig. 8) are quite as interesting in their vaulting as the nave. A single broad aisle on either side, which apparently opened into the nave through lofty arches rising almost to the clerestory, and which probably had transverse arches with ramping walls carrying half gable roofs, was altered when it was determined to vault the church. In doing this, two arches with a solid wall above were placed under each of the original arches of the nave arcade, a slender column built up in the center of each of the original bays, and upon the pseudo-double side aisles thus formed, compound groined vaults were constructed in a manner best understood from the photograph (Fig. 8). Except for those just mentioned there are but few Romanesque churches,—outside of Italy and Sicily,—in which the nave is covered by a series of domes.[29] But because of the powerful Byzantine influence, these latter countries contain a large number of churches of semi-Byzantine, semi-Romanesque character, some of which are as late as the thirteenth century.[30] Most of these are so distinctly Byzantine that they do not properly fall within the province of this book, in spite of their late date; but others, like the cathedral of Molfetta,[31] have a vaulting system quite closely allied to the Romanesque.[32] In this particular cathedral, a nave of three square bays is covered by three domes, one on flattened spherical pendentives, the others on niche-head-squinches. Two of them rise from drums and unlike their Byzantine prototypes, they are all of stone.[33] Moreover, the side aisles are covered with half tunnel vaults on full transverse arches, the crown of the vaults together with the nave walls above them acting as admirable buttresses for the domes. A system not quite so logical exists in the aisles of the church of San Sabino at Canosa (1100), where there are full tunnel vaults which do not serve so adequately as buttresses. Pyramidal Vaults
Although not vaulted with domes, the church of Saint Ours at Loches in France (Indre-et-Loire) (Figs. 9 and 10) has a close connection with such churches as those of Perigord and Notre Dame-du-Puy. This collegiate church was probably constructed a little before 1168, and originally consisted of a nave divided into square bays by transverse arches of pointed elevation and side aisles which have now disappeared. Each nave bay is converted from a square into an octagon by flat triangular pendentives on very small trumpet arches. But instead of domes, the builders of Saint Ours substituted a hollow octagonal pyramid of stone over each bay. Such a system, while presenting the same aesthetic objection as that of Le Puy, had greater structural advantages. The pyramids could be built entirely without centering, and exerted almost no outward thrust, while the stones of which they were constructed could be faced on the exterior (Fig. 9) as well as the interior, and the steep roof thus formed provided adequate drainage for the rain and snow of the region.[34] Tunnel Vaults If the dome played but a small part in Romanesque architecture, such was not the case with the tunnel vault. Almost as old as civilization itself, this method of vaulting had been employed to a greater or less extent in every age from the Egyptian period to that of the Carolingian Empire. It is natural, therefore, to find it the principal method in use during the entire Romanesque era. Nor is it necessary to trace its history back to Persian or Armenian sources. The builders of the eleventh and subsequent centuries had plenty of examples nearer at hand. Roman vaults, some of them of stone, were still in a good state of preservation in many parts of the western world, and almost every country or province possessed examples dating from Carolingian days.[35] It is not the use of this roofing system, therefore, but the skill with which it was adapted to the naves and aisles of churches of basilical plan, that furnishes the most interesting features in the study of Romanesque tunnel vaulting. In fact, so distinct are the combinations and methods employed in different regions, that they constitute veritable architectural schools which may be classified and separately discussed.[36] Romanesque Schools of Tunnel Vaulted Churches The four major schools lie in France and center around the ancient provinces of Provence, Poitou, Auvergne, and Bourgogne, whence they derive their names. All four are comprised in practically the same period,—namely, the eleventh and part, at least, of the twelfth centuries,—and it would be impossible to arrange them in any chronological order. But from its resemblance to the Roman monuments in the midst of which it grew and the fact that it had comparatively little structural influence upon the other schools, Provence will be the first to be considered. The School of Provence The cities of Arles and NÎmes had been important Roman provincial centers. Moreover, they still retained, and to this day possess, a large number of Roman monuments whose influence upon the Romanesque churches of the eleventh and twelfth centuries is plainly apparent. Thus vaults which carry directly the tiles of the roof, single aisled churches resembling the little Nymphaeum, or so-called temple of Diana at NÎmes, the employment of flat pilasters in place of the more usual applied shafts of curved section, and a host of minor details all reflecting classic usage are marked characteristics of this school. Provence Churches of the First Type When considered from the point of view of vaulting, the churches of Provence fall into five distinct groups. The first, illustrated by the chapel of Saint Gabriel near Tarascon (Bouches-du-RhÔne),[37] is composed of churches with no side aisles. These are covered with tunnel vaults of semicircular or pointed section, with or without transverse arches and carrying directly the tiles of the roof. The supporting walls are frequently strengthened by a series of interior applied arches in one or more orders thickening the wall at the impost of the vault. Outside of this interior buttressing, which has already been seen in Perigord, the churches of this type are of little structural interest. Provence Churches of the Second Type In the remaining groups, side aisles are always present and these have four distinct vaulting systems. In the first, tunnel vaults are employed throughout the edifice. Saint Nazaire[38] (after 1090), the former cathedral of Carcassonne (Aude), though somewhat removed from the center of the school, illustrates this system. Both nave and aisle vaults rise from the same impost level. The vault of the nave is slightly pointed, those of the aisles are semicircular, and both have transverse arches. It is a simple and practical method of construction, since the aisle vaults furnish admirable abutment for that of the nave, and all three are covered by a gable roof of masonry resting directly upon the vault crowns. Its one great fault is the absence of direct light in the nave, a condition which introduces the problem of lighting a tunnel-vaulted church. The Lighting of Tunnel-Vaulted Churches This problem was second only to that of constructing the vaults themselves and, furthermore, it had much to do with the forms which these assumed and even with the plan of the church. When there were no side aisles, windows were cut directly through the outer walls, but to introduce a clerestory above an aisle arcade involved a number of structural difficulties. The side aisle vaults no longer aided in supporting that of the nave, and in fact exerted an inward pressure at a point below its impost where such pressure was most difficult to offset. At the same time, the outward thrust of the central tunnel vault was increased in proportion to its elevation from the ground. The simplest method of meeting these difficulties was to increase the thickness of the clerestory walls, or add simple salient buttresses and trust to good construction to offset the increased thrusts. This was the method adopted by most of the Romanesque builders.[39] It was only in the school of Bourgogne, and under its influence, that the problem received a better solution—which will later be discussed at length—and not until the Transitional and Gothic periods that it was completely solved by dispensing entirely with the tunnel vaults. While its chief effect was upon vaulting, the lighting problems frequently affected the plan of the church as well. When the nave was without direct light, the aisles were almost always narrowed to permit light to enter from windows in their outer wall. Double aisles were practically impossible,[40] unless the inner aisles had triforium galleries supplied with windows.[41] Nor did the problem of lighting enter merely into the construction of simple tunnel vaulted churches. It was involved with that of all kinds of vaulting throughout the entire Romanesque and Gothic periods. Transverse tunnel vaults like those of Tournus, groined vaults like those of VÉzelay, the development of the Gothic chevet from the half domed apse, and the systems of ribbed vaulting which are frequently found in the crossings, aisles, and ambulatories of Gothic churches, all are closely related to the lighting problem. Provence Churches of the Second Type continued Returning to Provence, it will be recalled that Saint Nazaire at Carcassonne was described as a typical example of the second class of churches of this school, entirely tunnel vaulted, with narrow side aisles whose lateral windows afford the only light with which the nave is supplied. There are, however, a few churches, vaulted like Saint Nazaire, in which the builders introduced a clerestory. Among these is the abbey church of Saint Guilhem-du-DÉsert (HÉrault) (rebuilt at the end of the eleventh century).[42] Here the clerestory is of considerable height, the heads of the windows lying beneath the imposts of the tunnel vaults, a fact which renders this church one of the most developed of the school. Yet this development lies merely in the presence of the windows, and not in any structural advances which made their presence possible. It was because of the excellent masonry of the heavy walls and piers, that the Provence builders dared to attempt this innovation. The vaults themselves are no lighter than before and still carry the entire weight of the roof. In fact, the whole system is one of inert stability, analogous to Roman construction, and exhibits little if any advance toward the elasticity and balanced thrusts which were to characterize Gothic architecture. Provence Churches of the Third Type The churches in the third Provence group differ from those in the second only in having half tunnel vaults in the side aisles, but this difference is sufficient to change to some extent the character and methods of construction. In the simple churches of this type where there is no clerestory as, for example, in the western portion of the little church of Saint Honorat, belonging to the monastery of the Isle-de-LÉrins (Alpes-Maritimes),[43] the half tunnel vault of the aisles furnishes better abutment for that of the nave than the full tunnel vaults of the second type, and at the same time permits loftier arches to be constructed in the nave arcades, giving a better distribution of light without raising the imposts of any of the vaults. When, however, a clerestory is added, as in Saint Trophime at Arles (first half of the twelfth century), the inward pressure of the aisle vaults is even more severe than in Saint Guilhem-du-DÉsert and at the same awkward place, so that the only structural advantage at Arles lies in the added height of the nave arches. It is a noticeable feature of Saint Trophime that the aisles have full, instead of half arches[44] used transversely beneath the vaults, very probably because the former exerted less inward thrust, and could also be weighed down by a solid wall which increased the rigidity of the structure by tying the pier of the nave arcade to the outer wall, and strengthened the clerestory for the support of the high vault. The system has already been noted in the cathedral of Molfetta,[45] and will be found repeated either in the triforia or aisles of a number of Romanesque churches of different schools.[46] Provence Churches of the Fourth Type The employment of a three-quarters tunnel vault over the aisles renders the fourth group of Provence churches a cross between the second and third. Like them it contains examples with and without a clerestory. Of these the cathedral at Vaison (Vaucluse)[47] (twelfth century) illustrates the former, and the abbey church of Silvacane (Bouches-du-RhÔne) (second half of the twelfth century)[48] the latter form. The advantage of the three-quarter type lies in the fact that it exerts less thrust against the inner wall than does the half tunnel and still makes possible loftier arches in the nave arcade compared to the height of the aisle vault than does the full tunnel vault. But these slight advantages are offset by its ugly appearance, and it was never in any sense popular. Provence Churches of the Fifth Type The system of the fifth type of the school of Provence is that of a tunnel vaulted nave with side aisles covered by transverse tunnel vaults. This method is, however, so different from the other four and was so widely extended,—largely through Cistercian influence—that it can hardly be said to be inherent in any one school, but rather to constitute an individual group of churches which will be separately considered. From the foregoing discussion of the entire school, it will be seen that the builders of Provence produced very little that was original in vault construction. It was not a school of progress, but rather one of conservative adherence to the Roman tradition of the province around which it centered. Its most progressive feature was, perhaps, the preference it displayed for the pointed tunnel vault,[49] and this may be explained by the fact that the vault in Provence generally carries directly the tiles of the roof and less masonry was necessary to carry a pointed vault up into a gable than would have been the case with one of semicircular section. One further preference, which shows the structural sense of the Provence builders, is that for transverse arches under the vaults, which not only make possible lighter masonry in the vaults themselves, but also lessen the centering necessary for their construction. Vaults Similar to those of Provence in other Romanesque Churches Such methods of vaulting as those just described are not confined to Provence. In Poitou, for example, there is a group of churches with half-tunnel vaults in their side aisles. Some of these, like Saint Eutrope at Saintes (Charente-InfÉrieure)[50] (eleventh century) and Aigues-Vives (Loir-et-Cher),[51] have corresponding half arches, others, like Parthenay-le-Vieux (Deux-SÈvres),[52] (cir. 1129) have full transverse arches beneath these vaults. Moreover, in Auvergne the triforium is regularly covered with a half tunnel vault buttressing the tunnel vault of the nave, and in a few instances, as at Culhat (Puy-de-DÔme),[53] the side aisles are in one story with similar vaulting. There are also many instances outside of Provence in which the aisles have full tunnel vaults. Between Auvergne and Bourgogne there is an example in the abbey church at Souvigny (Allier) (eleventh century) (Fig. 11), and such a system may quite possibly have been employed in the aisles of Cluny[54] and in those of the choir of Saint BenoÎt-sur-Loire (Loiret)[55] (second half of the eleventh century). Even in England it occurs in the Tower Chapel at London[56] (begun 1078), and is also found in Poitou at Melle (Deux-SÈvres), Saint Pierre[57] (early twelfth century), where the vaults are pointed, and at Lesterps (Charente),[58] where they are of semicircular section. The three-quarter tunnel vault also is not confined to Provence for it appears as far north as Saint Genou (Indre) in the eleventh century. The foregoing examples serve only to indicate that such systems as these which are inherently simple in construction came, very naturally, to be widely employed during the Romanesque era. Where they originated it is impossible to say, but the fact that they are so elementary in principle and often vary in some of their structural characteristics[59] may indicate that they were developed independently and contemporaneously in various localities. Naves with Tunnel Vaults and Aisles Groined The next three schools of Romanesque architecture have one feature in common, namely, the employment of groined vaults over the side aisles. But the form which these assume and their relations to the tunnel vaults of the nave differ sufficiently to distinguish the churches of Poitou, Auvergne and Bourgogne from one another. The School of Poitou The chronology of the churches of Poitou is somewhat obscure, but the vaulting principles of the school were well developed early in the eleventh century, to which period a number of the existing churches belong. Their naves are tunnel vaulted and without a clerestory, the light entering through windows in the outer walls of the aisles, which are narrow and high and covered with groined vaults rising from the imposts of the arches opening into the nave. The entire church has a single-gabled exterior roof of wood and tile, its rafters supported near their centers by a wall above the nave arcade, and thus not resting directly upon the extrades of the vaults.[60] Certain minor structural differences make it possible to divide the churches of Poitou into two groups. The first is composed of the earlier churches, of which Saint Savin-sur-Gartempe (Vienne) (begun cir. 1023) is the best and perhaps the only existing example. In it, both nave and aisle vaults are without transverse arches. All the vaults are semicircular in section, and those of the aisles[61] have their transverse surfaces continuous with the soffits of the nave arches.[62] This gives them the flattened groins so characteristic of Roman architecture. Such a system as this required an extensive wooden centering, and it is not surprising that the builders of Poitou soon introduced transverse arches beneath the vaults,—perhaps through the influence of Lombardy, where they were in use as early as the tenth century[63]—thus producing a group of churches which form the second type of the school. Notre Dame-la-Grande at Poitiers (Vienne) (early twelfth century), is an early example of this class. Transverse arches are employed throughout the church, not only strengthening the vaults but making it possible to save centering by using the same form for each successive bay and at the same time reducing to some extent the thickness of the web by thus breaking it up into smaller units.[64] Toward the second half of the twelfth century the system was still further improved by the introduction of pointed arches and vaults in both nave and aisles, as for example in the abbey church of Cunault (Maine-et-Loire). The flattened type of groin has here been abandoned, though the vaults are not of domed-up type. Such doming is to be found in Poitou, however, in Saint Pierre at Chauvigny (Vienne),[65] probably with the intention of saving centering, as in Byzantine architecture. But even though the builders of Poitou made some progress in vaulting, they never attempted to solve the associated problem of getting direct light in the nave. Hence such progress was but slight from the earliest to the latest churches of the school.[66] The School of Auvergne
The Origin and Use of the Triforium Gallery in Auvergne One of the distinguishing features of the typical churches of Auvergne is the presence of a second story or triforium gallery above the side aisles. To account for its presence a number of theories have been advanced. That such galleries were not intended for congregational purposes, at least in the early churches of the school, is evident from the fact that they are but dimly lighted and accessible only by narrow staircases in dark corners. They may have been used for storerooms or treasuries for relics brought by pilgrims,—a possibility which is strengthened by the fact that they ceased to be built in the thirteenth century when the era of the Crusades was past,[67]—or they may have been useful places from which to defend the church, corresponding in this respect to the room frequently found in the second story of Romanesque towers.[68] But whatever their use, they would seem, in Auvergne, at least, to have originated on purely structural grounds. The expedient of dividing the openings from the nave of the church to the aisles into two stages, with the evident intention of thus reducing the height of the piers and even of making lighter piers possible, was employed in a number of churches both earlier and later than those in Auvergne. It may even be in part the explanation of the double colonnade in the Lateran Baptistery, and the upper stories in the chapel at Aachen, and the abbey churches at Essen, Nymwegen, and elsewhere. In any case, it explains the system of two stories of arches in the Carolingian church of Saint Michael at Fulda (818-822),[69] and in the early Romanesque churches of Vignory (Haute-Marne)[70] (eleventh century), MontiÉrender, (Haute-Marne)[71] (early eleventh century), and Chatel-Montagne (Allier)[72] (early twelfth century), and probably also in Saint Pierre at JumiÈges (Seine-InfÉrieure)[73] (cir. 940).[74] A significant fact in connecting these churches which are wooden roofed, with the vaulted churches of Auvergne, lies in their geographical distribution. While the earliest examples such as Fulda lie in the Carolingian region, the latter examples, JumiÈges, Vignory and MontiÉrender lie but slightly north of Auvergne, while Chatel-Montagne is actually in this province.[75] What is more natural to suppose, then, than that the vaulted churches of Auvergne were based upon these earlier churches, and that the nave arcade in two stages was retained even when both aisles and nave were covered with vaults? Furthermore, it would then be perfectly natural that the builders should have built these vaults in two stories corresponding to the two stages of arches, since they would have promptly recognized the great advantage gained by this system, which stiffened the interior and exterior walls for the added weight which the high vaults brought to bear upon them, without injuring to any extent the appearance of the church.[76] This seems all the more plausible when the fact is considered that the churches of Auvergne generally have broader aisles than those of Poitou or Provence. This may also have been a heritage from the early churches with two-storied arcades and wooden roofs just mentioned,[77] and in any case it further explains the system of aisle vaults in two stories. For, while the vaults of narrow aisles might be raised a considerable distance from the ground without danger from excessive thrusts, in wide aisles they would have exerted such thrusts and pressures on piers and walls as to have rendered their support most difficult, particularly when they carried directly the tiles of the roof as in Auvergne. The School of Auvergne continued As to the actual vaulting system of the Auvergnate churches, it is as follows. In the nave, heavy tunnel vaults resembling those of Provence in that they usually carried the roof.[78] Otherwise the churches are more like those of Poitou in the form of the piers, the almost universal absence of a clerestory, and the employment of vaults of semicircular section with transverse arches, as in the early churches of the second class in that school. In the triforium, the builders realized the advantage gained by the use of a half tunnel vault as an offset to the nave thrusts and as a means of best filling the space beneath a single gable roof,[79] and this is therefore the universal method. At times this vault is borne on full semicircular transverse arches,[80] and at others on those which follow its curve.[81] In the side aisles, groined vaults were employed because they were the only kind which could be built without cutting into either the triforium or the side wall windows. In form they closely resemble those of Poitou and were provided with transverse arches. Churches of the Auvergne School The church of Notre Dame-du-Port at Clermont-Ferrand (Puy-de-DÔme)[82] (Fig. 12) (cir. 1100) has the Auvergnate characteristics just described. Its great fault lies in the darkness of the interior, a darkness more pronounced than that of the churches of Provence or Poitou because of the width and lowness of the aisles with the consequent distance of the lateral windows from the nave and the fact that they cannot be cut very high above the floor. The windows of the triforium are also small,[83] and their light is almost entirely confined to the gallery by its floor and by the smallness of the arches opening into the nave. This fault was remedied in the choir, where the light was most needed, by doing away with the triforium, and placing a clerestory beneath the half dome of the apse.[84] As a further improvement a lantern was placed over the crossing.[85] In certain churches of the school like Saint Sernin at Toulouse (nave twelfth century), the triforium was increased in size, perhaps in order that it might be used for congregational purposes, but more probably because larger windows were absolutely necessary in this portion of the church for the sake of the lighting. This theory is strengthened by the fact that Saint Sernin has double side aisles and the lateral windows are therefore too far away to light the nave. These added aisles are covered with vaults of regular Auvergnate character, even to the extent of half tunnel vaults beneath their roofs, and the remainder of the church corresponds to the structural standards of the school.[86] Churches of Auvergne with a Clerestory Although it might seem from the foregoing pages that the builders of Auvergne were very backward in structural technique, there are a number of churches in the school which have a clerestory in the nave. Among them is Saint Étienne at Nevers (NiÈvre)[87] (end of the eleventh century),[88] in which the clerestory is obtained by raising the wall above the triforium arches just high enough to permit the introduction of comparatively small windows with their heads rising above the impost of the vaults.[89] The principle is the same as that in Provence, and no structural innovation is involved. The builders merely relied upon heavy piers and walls and salient buttresses to bear the added thrust which the tunnel vaults, thus raised, produced. That their reliance was not especially well founded is proved by the numerous cracks in the masonry. The School of the Loire The introduction of a clerestory in tunnel-vaulted churches was not yet scientifically accomplished, and it remained for the school of Bourgogne to find the best possible solution of the problem. But this solution would seem to have been reached only after some intermediate steps had been taken which may, perhaps, be traced in a number of eleventh century churches. Two of these lie slightly to the north of Poitou and Auvergne and strongly reflect the influence of these neighboring schools. These churches, together with others in the same general region, may perhaps be said to constitute a school of Romanesque architecture, which might properly be termed the School of the Loire. The first of these is the small church of Saint Genou (Indre).[90] It is a combination of the types of Auvergne and Poitou except that the tunnel vault of its choir is raised on a clerestory wall pierced with good sized windows. Its aisles are in only one story, and, instead of being groined, are covered by three-quarter tunnel vaults perhaps showing the influence of such Provence churches as those of Silvacane and Vaison. The whole system shows an advance in structural skill in several particulars. In the first place the aisles are built low, and with columnar piers close together, thus insuring the support of a heavy triforium wall. This wall is lightened in appearance but not structurally weakened, by a wall arcade opposite the vaults and roofs of the aisles, and is sufficiently thick at the clerestory level to be pierced with window openings and still afford an excellent impost for the tunnel vault. This, in turn, is built of light material like the vaults of Poitou. With exterior salient buttresses, the system is complete. Its only important drawbacks are the closeness of the supporting piers and the necessity of keeping the whole choir rather low to avoid excessive thrusts. The second church lies between Saint Genou and the school of Bourgogne. It is the abbey church of Saint BenoÎt-sur-Loire (Loiret), begun in 1062 and possessing a choir, transepts, and porch, dating from the second half of the eleventh century. Its choir (Fig. 13) closely resembles that of Saint Genou in every particular, except that the aisles have full tunnel vaults and the church as a whole is larger with a much more lofty nave of greater span.[91] Such a system as that of Saint Genou and Saint BenoÎt is produced by the extension of the elevation so frequently seen in the apses of the churches of Poitou and Auvergne to embrace the sides of the choir as well. The columnar piers and small arches used are like those in the apse rather than like those in the remainder of the church. The builders seem, however, to have failed to realize that walls which would support the half dome of the apse would not necessarily prove sufficiently strong to resist the thrusts of a tunnel vault. In fact, in spite of its apparent advance, the vault of the choir of Saint BenoÎt was only prevented from falling by the addition of transverse arches and flying-buttresses at a date subsequent to the completion of the church, and the vault of the nave of Cluny, which was quite possibly similar, actually fell in 1125.[92] It remained for the twelfth century builders of Bourgogne to take the final steps which were to carry the system of tunnel vaulted naves with direct light to its highest development. Fig. 13.—Saint BenoÎt-sur-Loire, Abbey Church. The School of Bourgogne It is most unfortunate for a study of the school of Bourgogne that the mother church at Cluny (SaÔne-et-Loire) should have been almost totally destroyed in the French Revolution. This great church was begun in 1089 and must have been finished in 1125, for the nave vaults fell in that year and were rebuilt before the final consecration in IIVO. What its original vaulting system was is difficult to say. Reber[93] says that it was probably vaulted like the churches of Auvergne with inner aisles in two stories, but Rivoira[94] states that both the nave and aisles had tunnel vaults on transverse pointed arches. The exterior view,[95] and the model which fortunately remains, would correspond with either arrangement.[96] The important facts to note are that the nave had a clerestory, and that the nave vault was strengthened on the exterior by carrying up the clerestory walls to exert a downward pressure at its haunch, a most important structural advance over the exterior wall of Saint BenoÎt-sur-Loire.[97] The developed system of Bourgogne may be seen to advantage in the abbey church of Paray-le-Monial (SaÔne-et-Loire) (Figs. 14, 15), which dates from the early twelfth century and is thus only slightly later than Cluny itself. Its nave is wider and loftier than any yet seen in which a tunnel vault was used, though not equal in size to that at Cluny, which was thirty-two feet wide and ninety-eight feet high. All the structural arches are pointed, but those used for windows, doors and decoration are still round headed.[98] The clerestory, while it has only moderately large windows, is so high above the ground as to render the support of the vaults above it exceptionally difficult. This difficulty was overcome, first by giving the vault a pointed section and thus reducing the thrust; second, by building as light a web as possible and covering it with a wooden roof; third, by using tie-rods of wood or metal, running along near the impost of the vault in the thickness of the walls, thus to a certain extent concentrating the pressure upon the piers; and, finally, as has already been stated, by carrying the exterior walls of the church to a point considerably above the window heads (Fig. 15), thus obtaining a downward pressure which offsets the outward thrusts.
The side aisles of the school of Bourgogne are also worthy of mention. They are usually covered with groined vaults, in many cases of slightly domical form. Whether this method came directly from Lombardy where there exist early examples of its use, or whether it came in through the influence of Poitou and Auvergne which had come into close contact with Carolingian architecture, is an open question. It seems quite likely, however, that, since the Byzantine builders developed this type and transmitted it to the Carolingian builders of the Rhine valley, it should have passed from there into France and spread over the three northern-central schools as it did over Lombardy. Regardless of its origin, it became the standard type in all the important churches of the Cluniac region. Occasionally, as at Souvigny (Allier) (possibly eleventh century), the enclosing arches are of stilted round headed form, a type which is also found as far north as VÉzelay (Yonne) La Madeleine (after 1140) (Fig. 16). Neither of these churches, however, is near the center of the school,[99] and the pointed structural arch as used in the abbey church of Paray-le-Monial (Fig. 14) is the common form. The system employed in Bourgogne marks the highest development attained in the use of a tunnel vault running the length of the nave. In the Ile-de-France a few instances might be cited[100] in which a system like one of those already described was used, and the same is true of certain Romanesque churches outside of France, but in none of them is any new structural method introduced. The tunnel vault was even used occasionally as late as the thirteenth century,[101] but the examples are generally small and insignificant. Churches with Transverse Tunnel Vaults Over the Nave Besides the methods which have just been described and which were so localized as to form veritable Romanesque schools, there remain a number of churches falling into two groups in which transverse tunnel vaults replace those running longitudinally either in the nave or aisles. The first and smaller group contains those in which such vaults were used over the nave. Of these, the most important example is Saint Philibert at Tournus (SaÔne-et-Loire),[102] a church of considerable size and of early date (dedicated 1019). Cylindrical piers and transverse arches divide the nave into rectangular bays each of which is covered by a transverse tunnel vault with a window in the clerestory wall at either end. Excellent light is thus obtained and the thrusts of the vaults admirably counteract one another. In fact, the system is so logical that it is surprising that it gave rise to so few imitators.[103] The explanation may perhaps lie in the lack of apparent continuity in the vault, a fault which this method shares with that of Le Puy. As to its origin, it may go back to such Persian monuments as Tag-Eivan, or to Syrian copies of Sassanian work with the substitution of stone for brick as Choisy suggests,[104] though it is not unreasonable to think that the builders of Tournus originated the system since it involved no unknown structural principles. The aisles of Saint Philibert furnish one of the rather rare examples of the employment of interpenetrating vaults.[105] Churches with Transverse Tunnel Vaults Over the Aisles The second group is much larger and more widespread, and comprises all the churches employing transverse tunnel vaults over the side aisles. The examples belonging to the school of Perigord have already been discussed,[106] and mention has been made of the fact that there are possibly enough of such churches in Provence alone to constitute a fifth type in that school.[107] But the system is too widespread to be attributed to any one province. It is undoubtedly a product of Roman and very early mediaeval architecture, for it is to be seen in such buildings as the Basilica of Maxentius at Rome, and in a modified, ramping form at Aachen.[108] Its structural advantage lies in the large space which the tunnel vault affords for windows in the outer wall thus lighting both the nave and aisles. Among the many examples are the parish church of Chatillon-sur-Seine (CÔte-d’Or)[109] of the twelfth century, the abbey churches of Hauterive (Savoie), Ronceray[110] (vaulted in 1115), BÉnÉvent-l’Abbaye (Creuse),[111] and the cathedral of Lescar (Basses-PyrÉnÉes),—in which, however, the vaults are an addition to a primitive construction.[112] In the church at Fontenay (CÔte-d’Or)[113] (before the middle of the twelfth century) concealed flying buttresses appear over the transverse arches between the aisle bays, thus aiding in securing a more even abutment for the continuous thrust of the tunnel vault of the nave. A few churches like Cavaillon,[114] and the cathedral of Orange (Vaucluse),[115] have tunnel vaults over rectangular bays flanking the nave but not connected by arches to form side aisles. The vaulting of the ambulatory gallery of Mantes cathedral, of the aisles of Fountains Abbey in England, and possibly the original vaults of the aisles of Saint Remi at Reims[116] were also transverse tunnel vaults. These latter churches differ from the ones previously mentioned, however, in that they are not tunnel vaulted in the nave and, moreover, are constructed with a clerestory so that the side aisle vaults do not serve the purpose outlined in the account of tunnel vaulted churches in the preceding paragraph. Tunnel Vaults with Cross Ribs This brings the discussion of the standard methods of tunnel vaulting to a close, but there remain two curious churches in which cross-ribs were added beneath the surface of simple tunnel vaults. One of these is at Lusignan (Vienne),[117] and the other at Javarzay (Deux-SÈvres). Both date from about 1120 to 1140 though the ribs may be a later addition to give the appearance of ribbed vaulting which was introduced at about this time. Naves with Groined Vaults Although usually confined to the side aisle bays, there are a few Romanesque churches in which the builders of the eleventh and twelfth centuries placed groined vaulting over the nave. The scarcity of such examples is due primarily to the difficulty of meeting the severe outward thrusts of a groined vault raised over bays of considerable span and at a point high above the ground. In the side aisles where the vaults were comparatively low, the exterior wall could be thickened by salient buttresses, and the piers strengthened by the weight of the wall above in a manner to offset the thrust, but in the nave the problem was more complicated. The builders had not yet invented the flying buttress. Hence, when they attempted groined vaults at all, they blundered along trusting that the inert mass of their walls and such timid buttresses as could be erected above the nave piers would provide sufficient offset for the thrusts even though these were now concentrated at four main points in each bay. Naturally the vaults frequently gave way and had to be reconstructed. In spite of these difficulties, the advantage of the groined vault in providing a clerestory whose windows might rise as high as the crown of the vault itself led to its occasional use. Groined Vaults Over Rectangular Nave Bays The vaults thus employed were of two rather distinct classes, those over rectangular nave bays which were usually but little domed up, and those over square bays which were generally distinctly domed in the Byzantine manner. Of the first type perhaps the best known example is the Burgundian church of La Madeleine at VÉzelay (Yonne), (Fig. 17) dedicated in 1104. Its nave is divided into a series of rectangular bays by transverse arches of semicircular section, and over each bay is placed a groined vault very slightly domed at the crown. To insure the stability of these vaults, the builders relied on the weight of the walls, which were carried up somewhat above the window heads, and on simple salient buttresses. To these exterior supports were added interior arches half imbedded in the walls above the clerestory windows (Fig. 17), furnishing one of the earliest examples of the use of wall ribs or formerets. The web of the vault does not, however, follow their extrados, but gradually breaks away from it toward the crown, with the apparent object of thus concentrating even more pressure upon the piers by stilting the wall line of the vault surface.[118] Even these precautions were not deemed sufficient, so iron tie-rods were employed, but these rusted and broke,[119] the vaults settled badly,[120] and if it had not been for the addition of exterior flying buttresses, which had meanwhile come into general use, the vaults would most certainly have fallen. Although not a structural success, VÉzelay did prove of advantage in turning the builders away from the tunnel vault,—and this, too, in Bourgogne where it had been most highly developed,—to a new type which presented problems whose solution was to lead to Gothic architecture. VÉzelay was, however, but little imitated in the Romanesque era, perhaps because of the almost contemporary development of the ribbed vault in Lombardy, Normandy, and the Ile-de-France. A few churches, such as Anzy-le-Duc (SaÔne-et-Loire)[121] did employ groined vaults over the nave but on a smaller scale and frequently with more pronounced doming. A more important and independent group of groined vaulted churches is to be found in Normandy. In this school, the churches were usually covered with wooden roofs though the aisles were occasionally groined. But there are three churches in which the choir also has groined vaults. These are, La TrinitÉ or the Abbaye-aux-Dames at Caen (Calvados) (cir. 1066), Saint Nicolas at Caen (cir. 1080), and Saint Georges-de-Boscherville at Saint Martin-de-Boscherville (Seine-InfÉrieure) (late eleventh and early twelfth century). The choir of the third of these churches, though later in date than the others, is more primitive in type, for it is covered by interpenetrating vaults, in which, however, the deep lunettes above the windows rise so nearly to the crown that the result resembles groined rather than tunnel vaulting. In both the other examples true groined vaulting is used, but at La TrinitÉ it is in practically square bays, and carried by walls running down to the ground,[122] making it easier of construction than that at Saint Nicolas[123] where the bays are rectangular and the choir has true side aisles. This church is similar in structural principles to La Madeleine at VÉzelay—except that the wall ribs are omitted,—and these two churches may be said to represent the highest point reached by groined vaulting with practically flat crowns during the Romanesque period. Other examples might be cited, ranging from such an unusual church as Saint Loup-de-Naud (Seine-et-Marne) in the Ile-de-France,—which is of uncertain date,[124]—to churches as late as the thirteenth and fourteenth centuries, among which are Severac-le-ChÂteau (Aveyron) and Saint Pons-de-Mauchiens (HÉrault).[125] Occasionally, also, groined vaults were used in the crypt as at Saintes (Charente-InfÉrieure),[126] even when tunnel vaults were used in the upper part of the church, a peculiarity explained by the fact that underground it was easy to dispose of the thrusts which could not so readily be offset in the nave. The question of the origin of the method has frequently arisen and a number of writers, including Choisy,[127] suggest the East as a possible cradle of the style because of the numerous churches in Palestine thus vaulted, but Rivoira[128] shows rather conclusively that it was the Cluny influence which carried the method to the East rather than the reverse, a theory strengthened by the fact that the earliest example there, which is the church of Saint Anne at Jerusalem,[129] would seem to be after rather than before the beginning of the twelfth century.[130] Moreover it is quite reasonable to attribute the development of this advanced type of vault to the builders of Bourgogne themselves, for they were surely progressive enough to have taken such a step. Groined Vaults over Square Nave Bays Churches with groined vaults over square nave bays are much more numerous than those with rectangular bays, just described. The most important of these belong to the school of the Rhenish Provinces, which had, perhaps, clung to Byzantine and Carolingian traditions in this respect. As a rule the large churches of this school were originally planned for vaulting only in the side aisles.[131] These were usually divided into square bays by round headed transverse arches, and then each bay covered by a more or less domed up groined vault, which, from its size and form, might be erected with comparatively little centering.[132] There was no triforium gallery, but a wall with blank arches took its place beneath the clerestory windows. In many of the churches[133] shafts were carried up on the inner face of alternate nave piers, probably to support the cross beams of the roof, or possibly to carry transverse arches, but not to carry vaulting. By the early twelfth century, after numerous fires had played havoc with the churches, the Rhenish builders seem to have at last made an effort to replace the wooden roofs with vaults. In doing this, they sought a form of vault which would exert as little as possible of outward thrust and thus be stable at the considerable height at which it must be placed. The Lombard builders had by this time developed the domed up cross-ribbed vault, but, as has been admirably shown by Porter,[134] the ribs which they employed had for their sole purpose the saving of wooden centering, since the masonry of the vault proper was heavy enough to stand without their aid. It was natural then for the Rhenish builders, who copied their neighbors in Lombardy in many particulars,[135] to look to them for a method of vault construction, which they found in domed up vaults like those of Rivolta-d’Adda (1088-1099) or Sant’Ambrogio at Milan (cir. 1098). These the Rhenish builders chose as models, but being plentifully supplied with wood for centering, it would seem as if they purposely did not adopt the diagonal ribs, but built groined vaults of simple domed up type, placing them over square nave bays each corresponding to two aisle bays in the true Lombard manner. This system may be seen to advantage in the cathedral of Speyer[136] (probably vaulted cir. 1137-1140). With extremely heavy walls like those of the Rhenish churches, and with good masonry for their construction, such vaults proved comparatively safe even over naves of such a span as that of Speyer which is almost fifty feet in width. This account of the Rhenish school completes the discussion of groined vaulting as applied to the naves and choirs of Romanesque churches. The heavy walls and the general excellence of masonry construction which they required, together with the necessity for large interior piers, did not render them popular or widely used. Aisles with Groined Vaults in Lombardy and Normandy That the use of groined vaults was far more extensive in the aisles than in the naves of Romanesque churches has already been shown by the examples cited from the schools of Poitou, Auvergne, Bourgogne, and elsewhere. To these should be added a number of churches, chiefly of the schools of Lombardy and Normandy, which have groined aisles in combination with rib vaulted or wooden roofed naves. In Lombardy, where the naves are ribbed, this combination has been admirably explained by Porter[137] in connection with the use of wood for centering. Thus he shows that groined vaults, provided that they were sufficiently domed up, could be built over the small bays of the aisles and triforia with almost no wooden framework, but that when such vaults were attempted in the nave the bays were so large as to require a considerable amount of centering beneath the vault, and therefore the builders substituted permanent diagonal arches of very heavy character. The Norman groined aisles are, however, of a different sort, for they either have level crowns or are but slightly domed up in type. [138] The abbey church of JumiÈges (Seine-InfÉrieure) (1040-1067) is among the earliest examples of this construction and is the only Norman church with groined vaults in both the aisles and triforium.[139] La TrinitÉ at Caen[140] and the abbey church of Lessay (Manche)[141] are also Norman churches with groined aisles, in both cases with level crowns. In La TrinitÉ, as in the early churches of Poitou, the bays are not even separated by transverse arches.[142] In Saint Étienne at Caen, and in the choir of the cathedral of Gloucester, the aisles are vaulted in both stories like those of Auvergne, the lower groined, the triforia with half tunnel vaults, but it seems very probable that these latter were added only when vaulting took the place of the wooden roof in the central portions of the church.[143] Curious instances of the persistence of groined vaulting are to be seen in the triforia of such transitional churches as Saint Germer-de-Fly (Oise)[144] and VÉzelay, where the remaining portions of the church have ribbed vaults. For this persistence an explanation is later attempted.[145] Aisles with Semi-Groined Vaults An unusual form of aisle vault appears at Creully (Calvados)[146] (twelfth century), where the aisles are covered with a half tunnel vault intersected toward the outer wall by lunettes, which thus convert it into a semi-groined vault. Its obvious advantage lies in the combination of inward pressure, which it exerts in support of the nave vaults, with the added window space which it affords without increasing the height of the exterior walls. Ribbed Vaults The introduction of ribs beneath the diagonal intersections of groined vaulting gradually brought about a revolution in Mediaeval building, and transformed the massiveness of Romanesque construction into the light and graceful architecture of the Gothic era. Much has been written in an effort to discover the origin of the new system. It is not, however, the intention here to add to the number of theories advanced, except in an incidental manner, but rather to classify the various forms of ribbed vaulting as applied to naves, choirs, and aisles of the churches following immediately after those of the Romanesque period which have just been described. As a geographical basis is no longer practical for such a classification, because of the widespread distribution of the new method of construction, a structural basis will be substituted, and the vaults will be divided into two major groups according as they were used over square or rectangular nave bays, and then subdivided according to their minor characteristics. Ribbed Vaults Over Naves with Square Bays Lombardy affords the first examples of ribbed vaults over nave bays of square plan. According to Rivoira[147] the earliest are in the church of Santa Maria e San Sigismondo at Rivolta d’Adda[148] (before 1099), though this was closely followed by the more important church of Sant Ambrogio at Milan (between 1088-1128) (Fig. 18), which furnishes an admirable example of the Lombard type. Its nave is divided into four great square bays, each corresponding to two bays in the side aisles. (Plate I-a.) Of these the eastern bay is treated as a crossing and covered by a dome above a lantern on squinches, but the remaining three have four-part domed up vaults with heavy ribs of square section, used not only transversely and along the walls but also diagonally, thus forming a complete system or skeleton of arches beneath the vault surface in the manner of true Gothic architecture. But there are many reasons to believe with Porter[149] that the builders of Lombardy employed these ribs purely as a permanent centering of masonry,—which was less expensive than a temporary centering of wood in a country where the latter material was very scarce,—and that they failed to appreciate the fact that such ribs made possible a great reduction in the weight of the panels, or web. of the vault, and in other ways could be made to aid in reducing and concentrating its pressures. The masonry of the vault is still excessively
thick,—between sixteen and twenty inches,—and would stand equally well were the ribs removed. Moreover its thrust is so great that the builders dared not raise its imposts sufficiently high to admit of a clerestory beneath the formerets, and instead of rendering possible a lighter construction as Gothic vaults were destined to do, these vaults of Saint’ Ambrogio required for their support a wall forty inches thick and ramping walls above the transverse arches of the triforium together with interior tie-rods and wooden chains in the masonry[150] to offset their severe outward thrust. All these facts show that the Lombard vaults are still fundamentally Romanesque in type. Even in San Michele at Pavia (early twelfth century), where the system was a little more developed, in that a small clerestory was introduced, the principles were still the same as in Milan. As a matter of fact, the Lombard builders never made any further advance in the handling of ribbed vaults, and even went backward rather than forward. For the builders found that groined vaults of domed up type could be built so lightly as to require but little centering, and a return to this simple form was made in such churches as San Lanfranco at Pavia.[151] Later on, in the thirteenth and fourteenth centuries, French methods of ribbed vaulting were introduced, but throughout the whole period of Lombard supremacy the tendency was to avoid vaulting entirely, and when adopted, it was of the heavy character just described. The System of Alternate Supports The Lombard churches are important in the present connection, however, because of the method in which they are divided into vaulting bays. They furnish the earliest examples of the system of alternate light and heavy supports,—employed according to Cattaneo[152] as early as 985 in the three original bays of SS. Felice e Fortunato at Vicenza. This system of piers with alternate transverse arches produces one square[153] bay in the nave to two square bays in the side aisles, and it occurs not only in vaulted churches but also in others in which a wooden roof rests upon these transverse supports.[154] Its advantage in the vaulted churches is particularly important, however, and of a two-fold character. In the first place, it renders the four enclosing arches uniform, and it makes them as nearly as possible of equal span with the diagonals.[155] And in the second, it saves a considerable amount of centering by rendering possible the construction of a vault covering a space corresponding to two rectangular bays on four instead of seven ribs.[156] Outside of Lombardy, the four-part cross-ribbed vault over square nave bays was but seldom employed in churches with side aisles also divided into square compartments. It appears, however, in the cathedral of Le Mans, (Sarthe) (middle of the twelfth century), where it would seem to be due to the influence of the neighboring single aisled churches of Anjou,—which are later discussed,—and it was frequently used in reconstructing the vaults of the Rhenish school. In the Gothic period also, the system occasionally appears in a modified form, and naturally enough these revivals occur where Norman and Rhenish Romanesque had caused the principles of Lombard architecture to be strongly entrenched. Thus the church of Saint Legerius at Gebweiler[157] (cir. 1182-1200) furnishes a Rhenish, and the choir of Boxgrove Priory church (cir. 1235), an English application of this method. In the latter, the vaults are no longer highly domed up, and are therefore far removed from their Lombard prototypes, only the general division of the church reflecting this influence. Naves without Side Aisles More important by far, are the churches without side aisles but with naves in square bays with four part cross-ribbed vaults. This method is to be seen in the cathedral of FrÉjus (Var),[158] which is considered by Porter[159] to exhibit the earliest extant ribbed nave vaults in France. These are distinctly of Lombard type, and would seem to show a strong Lombard influence entering France from the south. It may possibly be that this same influence followed the route taken earlier by the dome on pendentives, and thus gave rise to the domed up ribbed vault so common in the churches of Anjou.[160] Of these latter, the cathedral of Saint Maurice at Angers (Maine-et-Loire) (Fig. 19), presents perhaps the best existing example. Its nave vaults which date from as early as 1150[161] are among the largest and finest in France, having a span of some fifty-six feet. As in Lombardy, the crown is highly domed up while to facilitate the construction of the web of the vault with the least possible centering, pointed diagonals and enclosing arches are employed. By this means the entire vault was constructed on the ribs with no centering at all for the lower courses, and a simple cerce, a device consisting of two curved boards sliding along each other, for those near the crown. At the same time the outward thrusts were greatly reduced by the pointed section of the vault. Anjou Ridge Ribs
Since the Anjou churches possessed naves of wide span, it is not surprising to find that their builders soon added ridge ribs beneath the vault. That these were not mere cover-joints to conceal an irregular intersection of the masonry, as Choisy suggests,[162] would seem to be proved by the fact that the courses meet in a straight line at the ridge in by far the greater number of Anjou churches in which they are employed,—for example in La Couture at Le Mans (Fig. 20), Airaines,[163] and numerous churches with small torus ribs, as well as by the fact that such ridge ribs are sometimes omitted even when the masonry is laid up in courses of equal width and therefore interpenetrating at the ridge, as in AvesniÈres (Mayenne)[164] near Laval. If not, however, primarily a cover-joint, these ribs did at least possess both a structural and decorative quality. In the first place they helped to keep the keystone of the diagonals rigidly fixed during the building process, and furthermore, they gave an absolutely straight line to the vault crown which was always difficult to adjust, particularly in a vault of large size. One of the best and earliest examples of the employment of such ribs appears in the nave of Notre Dame-de-la-Couture at Le Mans (Fig. 20) which dates from about 1200, and a later example is afforded by the church of Saint-Avit-SÉnieur (Dordogne),[165] where the vaults are of the thirteenth century and replace an original series of domes on pendentives of true Perigord type. In all of the Anjou vaults thus far discussed, the ribs are of comparatively heavy section and placed entirely beneath the vault surface, but there was to be a decided change in the thirteenth century. It has already been noted that domed up vaults could be erected almost without centering and exerted little if any pressure upon the ribs beneath them. Realizing this, the builders of Anjou soon began to reduce the size of the ribs until they became little more than torus mouldings running along the groin and ridge of the vault. As an actual fact, however, these torus mouldings were carved upon a sunken rib flush with the surface of the panel, which, if it no longer furnished a support for the vault, at least formed a sort of permanent centering dividing the surface to be vaulted into distinct severies and marking the line of their intersection in an absolutely correct curve. Such vaults are closely allied to those of groined type, the ribs playing practically the same part as those of brick in Roman concrete vaulting. Since, however, in the Anjou system the ribs always were merely a permanent centering which could easily be removed without destroying the vault, a sunken centering was quite as efficient in serving the purpose of vault division while the torus afforded a certain amount of surface decoration. Of this typical Anjou construction, there are numerous examples. At Poitiers, in the church of Sainte Radegonde the ribs are of reduced size but not quite flush with the vault surface and the same is true at Saint-Hilaire—Saint-Florent near Saumur (Marne-et-Loire),[166] while the choir and transept of Angers cathedral (Fig. 19), and the later bays of the cathedral of Poitiers furnish examples of the standard type. After a short period of experiment, the builders of Anjou became very skillful in the construction of these ribs and vaults and frequently employed them over bays of unusual plan and elevation as, for example, in the chapel north of the choir aisle in Saint Serge at Angers (Fig. 21). An instance of the influence of Anjou construction upon the neighboring territory, as well as of the relationship between this Gothic style and the Romanesque school of Perigord, may perhaps be seen in the Old Cathedral of Salamanca in Spain.[167] Here the three western bays of the nave are covered with ordinary domes but with diagonal ribs beneath them, while the two remaining bays have regular domed up Anjou vaults. The date of this cathedral, cir. 1120-1178, may, perhaps, explain this peculiar combination as being due to an Anjou-Gothic influence displacing one of Perigord-Romanesque, in much the same manner as such an influence displaced the Perigord-Romanesque architecture of western France. Square Nave Bays Outside of Lombardy and Anjou
Fig. 21.—Angers, Saint Serge. Besides its use in Lombardy and Anjou, the square nave bay with four part cross-ribbed vaults, was employed to some extent in other parts of Europe throughout the Gothic period.[168] Some of these are churches without side aisles, but aisles are more commonly found, divided into rectangular bays corresponding in number to those of the nave. Of the single naved churches, San Francesco at Assisi,[169] is a good example. Although dating from 1236-1259, its vault ribs are still heavy and almost square in section, as if derived from Lombard prototypes. But they differ in being of pointed section and in not giving to the vaults a domed up crown. In this they would seem to be examples of French influence upon Lombard tradition. Square Nave and Rectangular Aisle Bays An early church with square nave bays and ribbed vaults over rectangular bays in the side aisles (Plate I-b.), is to be found at Bury (Oise) (Fig. 22). It probably dates from about 1125, and is an important monument of the Transitional period. Its nave vaults are quite highly domed and in this respect seem somewhat Lombard, but their pointed arches and awkward construction indicate an effort on the part of the builders toward reducing this doming and a dawning consciousness of the value of the pointed arch in the construction of ribbed vaults. This is further shown in the side aisles. Because of the rectangular shape of the bays, the problem was presented of getting three sets of ribs of different span to rise to the same or practically the same height. Not being thoroughly familiar with the flexibility of the pointed rib, the builders at Bury were naturally somewhat clumsy in its use. Thus, the diagonals were made segmental in elevation to lower them to the level of the pier arches, while masonry was piled on the crown of the transverse ribs, or their voussoirs widened, to bring them up to the level of the vault panel.[170] A few such experimental steps as these at Bury, were all that were necessary to give the builders a mastery of the use of the pointed arch in ribbed vaulting. Ribs with Caryatid Supports
But there is another feature of the side aisle vaults which is worthy of note before turning to the more developed churches which resemble Bury in their arrangement of vaulting bays. This is the use of small caryatid figures which appear at the springing of the diagonal ribs (Fig. 23).[171] These would seem to serve a purely decorative purpose, perhaps to distract attention from the great size of the ribs behind them, or to give an apparent lightness to the vault itself by seemingly placing its burden upon such insignificant shoulders, or more probably still, the figures served to break the transition from shaft to rib by concealing the impost of the latter. Whatever their explanation, other examples besides those at Bury are to be seen. Of these, the angels—now badly mutilated—at the base of the ribs in the narthex of Saint Ours at Loches (Indre-et-Loire) (Fig. 24)[172] are especially interesting, and perhaps account for the tiny figures employed at the springing of the ridge ribs in a number of churches in Anjou, such as Angers, Saint Serge (Fig. 21), as well as for the larger figures in the apse of Notre Dame-de-la-Couture at Le Mans (Fig. 20).[173] It may even be through the influence of such figures as these that grotesques were used to support the small shafts in the arcade of the triforium passage in the cathedral of Nevers (NiÈvre) (Fig. 25).
Square Nave and Rectangular Aisle Bays continued
Returning to the churches later in date than Bury but vaulted on the same plan, it will be found that there are but few examples in France, an interesting fact for which an explanation will later be attempted.[174] The lower story of the Sainte Chapelle at Paris (cir. 1250) furnishes one of the rare examples, but here the nave and aisles are of the same height and so do not exactly resemble the system at Bury. Because of their narrowness, the side aisle vaults of the Sainte Chapelle did not furnish proper abutment for those of the nave, and the builders found it necessary to add tie-rods and even transverse half arches forming veritable interior flying buttresses at about half the height of the transverse ribs. This is, however, a most unusual arrangement. It was in Italy more than elsewhere that the method of square nave and rectangular aisle bays was adopted. Many of the largest churches of the Gothic period in that country were thus constructed. Among these, Santa Maria Novella at Florence (end of the thirteenth and beginning of the fourteenth centuries) has nave bays which are practically square, while the cathedral of Santa Maria del Fiore (fourteenth century) in the same city is a much larger church more strictly following the type.[175] This vast edifice presented such a vaulting problem that the builders did not hesitate to resort to the use of iron tie-rods to counteract the thrusts,—a subterfuge common enough in Italian architecture, of which the church of the Frari at Venice (after 1250) presents an exaggerated example. Lighting Problems in Naves with Square Bays Several factors enter into the lack of popularity of the vaulting system just described especially in the more northern countries, but the fundamental one would seem to be the difficulty of properly lighting churches thus covered. If an examination be made of the churches with a single broad nave and no aisles it will be seen that in Italy, where a comparatively small proportion of window space was necessary, the builders were content with a single window in each nave bay as for example, in San Francesco at Assisi. In France, on the other hand, the light thus admitted would have proved inadequate, and in such churches as the cathedral of Angers (Fig. 19) and Sainte Radegonde at Poitiers two windows were introduced under each wall rib. This is, however, an awkward arrangement because these windows do not properly fill the wall space, and though this is better accomplished by adding a circular window above the upright pair as was done in La Couture at Le Mans (Fig. 20), still the effect even then is not satisfactory and much solid wall which might be utilized for windows is wasted. Moreover, in a church with side aisles, the clerestory arrangement was still more troublesome since important structural difficulties were involved. To raise a great four part vault high above the aisles in order to obtain a large clerestory was no easy task because of the excessive thrust which such a vault exercised at its four points of support. In Italy, where the amount of light required was not great, a very low clerestory with small, circular windows, one to each bay, was all that was essential, and so in such churches as Santa Maria Novella and the cathedral at Florence the nave vault was placed at a point only slightly above the vaults of the aisles, and its thrusts offset by simple ramping walls beneath the side aisle roofs. Such a church in France would have been inadequately lighted, and even if a greater structural skill permitted the French to erect loftier clerestories than those in Italy, there remained the difficulty of arranging the windows to get the maximum of light and the best appearance. A single opening occupying the entire space beneath the wall rib would have been all head and no jamb. One upright window would have admitted too little light for a large nave, and two windows near together not only left a great deal of wall space unused but were most awkwardly placed in churches where one nave bay corresponded to two bays in the aisles as in Le Mans cathedral,[176] because they were not on an axis with the arches of the nave arcade. On the other hand, if placed on this axis, the resulting windows were necessarily of small size like those in such Rhenish churches as the cathedral of Speyer where a second stage of windows has been added one in the center above each lower pair in a far from satisfactory manner since it brings a window above the intermediate pier. Origin of Sexpartite Vaulting In view of these facts it is at least a reasonable assumption that the lighting problem had much to do with the discarding by the French builders of the simple square four-part nave vault. As a matter of fact, however, they did not exactly discard it, but evolved from it a vault in six cells, which, while it still retained the old division of the nave into square bays, each corresponding to two bays in the aisle, at the same time permitted the uniform treatment of these in elevation and made possible larger windows,—one to each aisle bay,—symmetrically placed and, in the course of time filling the entire space beneath the wall ribs. This six-part ribbed vaulting would seem to have originated early in the twelfth century, in the French province of Normandy. This province has already been mentioned as the center of a Romanesque school, which extended over the greater part of England after the conquest of 1066, and reached its height during the reign of Duke William, the Conqueror (1035-1087), when a vast number of churches were constructed, many of them of large size. These were in general wooden roofed throughout, though, occasionally, as has been shown,[177] groined vaults were used in the choir or aisles, or both. Toward the beginning of the twelfth century, however, the Norman builders determined to vault the naves of a number of these churches, among them the two abbeys at Caen, and the result of this determination was the evolution of the true and false six-part vault. Like the Rhine provinces, Normandy had always been strongly influenced by the methods of building developed in Lombardy. Whether this was due to the presence in Normandy of such men as Lanfranc,—who was born in Pavia in 1005 and became successively prior of Bec (1045-1066), abbot of Saint Étienne at Caen (1066), and archbishop of Canterbury (1070-1089), and who may have kept Normandy closely in touch with Lombardy,—or whether there were other more powerful influences, it is impossible to state, but in any event the architectural analogies between the two schools are striking. This is especially true of the type of shafted pier most frequently found in Normandy, and of the alternate system of light and heavy supports, which, while it does not characterize all the churches of the school, is found in many of them. Thus when the Norman builders determined to vault their great churches at Caen, one would naturally expect to find them turning to Lombardy for a method of vault construction, especially since Sant’ Ambrogio at Milan had been successfully completed at least a quarter of a century before their determination was made. And in fact this is probably what they did. But there were certain differences in structure between the churches of the two schools which made it impossible for the Norman builders to adopt unchanged, the heavy square, domed-up, cross-ribbed vaults of Lombardy. The first of these differences lay in the fact that the Norman churches were originally built for wooden roofs,—which may even have been in place, in many cases, when the vaults were begun,—while the Lombard churches were planned from the ground for their vaulting. The second difference was, that the Norman interior system possessed a clerestory window of considerable size centered above each of the arches opening into the side aisles,—that is two in each wall of what would be a square nave bay,—while the Lombard churches either had no clerestory at all, as at Sant’ Ambrogio, or one in which the windows were small and there was no attempt to center them as in San Michele at Pavia. It was natural that the Norman builders should have preferred to preserve their interior and exterior elevations as nearly as possible as they were when only a wooden roof was used, both to avoid the expense which would be involved in reconstruction and to preserve the large clerestory so essential in a northern country. To vault these churches and at the same time save this clerestory would seem to have been the problem, therefore, which the builders set themselves to solve. That they attempted to use the four-part vault in its solution will be seen from an examination of the seven vaulted churches[178] still remaining in which the old system of square nave bays is found, for in four of these a variant of four-part ribbed vaulting was employed while in the other three a new method was developed out of the four-part type. A study of the two abbeys at Caen will illustrate this. Of the two, Saint Étienne or the Abbaye-aux-Hommes (cir. 1064-1066) would seem to be the earlier as far as its vaulting is concerned and this would seem to date from about 1135. In its nave (Fig. 26) the alternate system of supports is employed, though all the piers are of almost the same section with a single shaft carried up the inner face. The aisles are in two stories and there is a clerestory with a single window in each bay. The nave was originally covered with a wooden roof. With this elevation existing before the church was vaulted it is quite possible to account for the form which this vaulting assumed. The first step must have been to divide the nave into square bays by transverse arches,—assuming that these were not already in place. The springing of these arches must naturally have been governed by that of those which opened into the crossing, and the level of their crowns, by the wooden timbering of the roofs,—which may well have been in place when the vaults were built. The result was that these transverse arches had to rise from a point as low as the clerestory string-course and could only be a slightly stilted semicircle in elevation. If the bays thus constituted were to be covered by four-part vaults of Lombard type, the next step would have been to erect diagonals of semicircular section thus doming up the vault at the crown, but at Caen such diagonals would have rendered necessary an entire change in the timbering of the roof because their intersection would have risen above the level of the trusses. Hence segmental diagonals were substituted. Upon this skeleton of ribs, it would have been quite possible to place a four-part vault, but the wall intersection of its panels would have cut off the heads of the clerestory windows. Several methods could have been used to avoid this. In the first place the severies could have been so shaped as to cut the walls in a curve above the window, but this would have given a flattened form to the panel and rendered it most difficult both to construct and to support when in place. A second expedient would have been to reduce the size of the windows but this, besides cutting off most necessary light would have utterly destroyed the splendid proportions between the horizontal divisions of the Norman interior. A third method would have been to move the windows toward the intermediate pier, but this would have destroyed the axis line of the aisle, triforium, and window arches, and was wisely rejected. Lastly the imposts of the ribs could have been raised, but even this would have introduced enormous structural changes: first, because it would have rendered necessary a change in the timbering, or else raising the entire roof of the church; second, because it would have placed the new impost out of level with the crossing arches; third, because it would have greatly increased the thrust of the vault, already most difficult to meet because of the segmental form of the diagonals and the lack of extensive knowledge of buttressing principles on the part of the Norman builders. To avoid all these difficulties and still retain the windows, a new method of vaulting was evolved. An intermediate transverse arch was added meeting the diagonals at their intersection, and above the triangular window cells thus formed, separate vault panels were constructed (Fig. 26). The line of the window heads was thus left undisturbed and the six-part vault created (Plate I-c.). False or Pseudo-Sexpartite Vaulting Of course, the foregoing suggestion that the six-part vault was evolved from four-part vaulting is largely conjectural, but an examination of other churches in Normandy would seem to show that the Norman builders almost always preferred to use the simple four-part vault in a slightly modified form whenever it was possible to do so and still retain the clerestory windows, rather than to employ the developed six-part type. This modified four-part vault may properly be termed false or pseudo-sex-partite. That it was not a mere prototype of the more developed six-part form would seem to be shown by the fact that it was built in churches both contemporary with, and subsequent to those with true six-part vaults. A good example of pseudo-sexpartite vaulting, for comparison with that of Saint Étienne (Fig. 26), is afforded by La TrinitÉ or the Abbaye-aux-Dames at Caen (Fig. 27). It would seem probable that the upper portions of this church were extensively rebuilt at the time when vaulting was added. In this rebuilding, concealed flying-buttresses were constructed beneath the side-aisle roofs, and these, together with the solid wall which replaces the open triforium gallery of Saint Étienne, made it possible to raise the level of the transverse arches of the vaulting to a point considerably above the clerestory string-course. Furthermore, since the wooden outer roof was probably built after the vaults, it was possible to use diagonals whose crowns were higher than those of the transverse arches, and still place them beneath the roof trusses. With such a skeleton of ribs as a basis, the builders proceeded to erect a four-part vault over each nave bay, or, in other words, enclosing two side aisle arches. Because of the higher impost of the vault ribs, the wall intersection of the vault cells easily cleared the window heads.[179] Curiously enough, however, the builders connected the intermediate piers with a transverse arch having a flat wall built upon it to the level of the crown of the longitudinal vault cells (Fig. 27). There would seem to be several explanations of this innovation. In the first place the pier system of La TrinitÉ is regular, not alternate, and a greater symmetry was obtained by having corresponding transverse arches connecting each pair of opposite piers. Moreover such arches had been used before 1114 in the church of Saint Georges at Boscherville, and quite possibly elsewhere as well,[180] beneath a simple wooden roof, thus tying together the lofty clerestory walls. In the second place, such arches had already been introduced at Saint Étienne, though for a different reason, as has been shown, and must have proved of value in keeping the keystone of the diagonals rigidly fixed, besides having become a characteristic of what was perhaps the major church of the school; and in the third place, such an arch with its wall above aided materially both in carrying a portion of the weight of the vault to the alternate piers and in affording permanent centering, which was needed in Normandy even more than in Lombardy because the Norman vault crown was never more than slightly domed up. Once introduced, this pseudo-sexpartite vault was not restricted to La TrinitÉ but was, as has been said, employed in no less than four of the seven square-bayed Norman churches. At Ouistreham (Calvados)[181] (vaulted cir. 1160), the impost was raised as in La TrinitÉ and pointed transverse arches were used, thus increasing the curve of the diagonals and improving the stability of the vault. More interesting still, however, are the two churches of BerniÈres-sur-Mer,[182] and Saint Gabriel (Calvados)[183] (both vaulted cir. 1150), for in them the builders have clung so tenaciously to the pseudo form in preference to the true that they have actually moved the windows of each bay toward the intermediate pier in order to use this method without raising the imposts. The latter is particularly interesting because of the extreme flatness of its diagonals for which the intermediate transverse arches must certainly have proved an added support. The preference of the Norman builders for this pseudo-sexpartite vault, even to the extent of moving the windows out of center to make its use possible, may find a further explanation than any yet given in the simplicity of its construction. A comparison of one window severy of Saint Étienne (Fig. 26) with one at La TrinitÉ (Fig. 27) will illustrate this point. In the former the surface of the vault is warped on either side of the window, while in the latter, the stone courses run almost directly back to the wall, so that the line of intersection is approximately the projection of one-half of the diagonal rib. Of course this second surface was far easier to calculate geometrically and could be put in place by less skillful builders than the warped surface required. It had, however, the fault of being in ill accord with the curve of the window head, but, on the other hand, it possessed the structural advantage of distributing the thrust of the vault over a large amount of exterior wall. This might seem a fault rather than an advantage, were it not that in such a primitive system as that of Normandy, thickness of wall was the greatest factor in abutment and thrusts which were widely distributed were thus more easily met than those which were concentrated within narrow perpendicular limits.[184] The advantage of the warped system in thus concentrating the thrusts was, in fact, realized only when inert stability which forms the keynote of Norman work gave way to the carefully balanced thrusts and counter-thrusts of Gothic architecture. The little church of Le Petit QuÉvilly (Seine-InfÉrieure)[185] (cir. 1156) would seem at first to disprove this Norman preference for pseudo-sexpartite vaults. The imposts of its arches are sufficiently high to permit of such a type, yet the real six-part vault was employed. The explanation of this would seem to lie in the geographical situation of the church, for it is not in Calvados, like the other examples, but in Seine InfÉrieure near Rouen, or in other words on the border of the Ile-de-France, where the six-part vault had been adopted with enthusiasm and used as early as 1140, or some fifteen years previous to the building of Petit-QuÉvilly, in the large abbey church of Saint Denis. It is also difficult to explain the use of the true form in the seventh of the vaulted churches, which is that of Creully (Calvados),[186] but the fact that it has the same low imposts as Saint Étienne at Caen combined with the evident purpose of the builders to keep the windows in the center of the bays may perhaps furnish an explanation of its appearance here. Development of Sexpartite Vaulting The true six-part vault, as used in Saint Étienne, was far from being perfect. In the first place, it possessed a number of inherent structural faults. These lie chiefly in the unequal distribution of thrusts, and the unequal size of the panels into which the vault is divided. From an aesthetic point of view, two other faults might be added: first, the decrease in the apparent length of the nave, due to the fact that it was divided into a few large bays, instead of twice as many smaller ones; and second, the fact that the crowns of the vault cells above the windows do not run out perpendicularly from the clerestory wall but at an awkward angle, thus greatly injuring the symmetry of the bays. Yet in spite of these drawbacks, which were common to all six-part vaulting, this system had a long period of popularity. There are, however, certain structural weaknesses in these early Norman vaults which were largely due to lack of experience on the part of the builders, and not to the form of the vaults themselves. Wall ribs were, for example, omitted, and the diagonals were made of segmental section, thus rendering unnecessarily severe the thrusts of the vaults. Moreover, such a church as St. Étienne was not planned from the ground for vaulting and the piers had not the proper arrangement of shafts. Last of all, the intermediate arches were of a rather ugly, stilted character, possibly so constructed with an eye to a better distribution of light, but in any event presenting an awkward appearance. All these faults were gradually overcome in the Transitional and Early Gothic churches of the Ile-de-France. Sexpartite Vaulting in the Ile-de-France That it should have been this province which favored the six-part system is most curious, for at a date almost contemporary with St. Étienne at Caen, ribbed vaults of rectangular plan had probably been constructed over the naves of Saint Étienne at Beauvais and the abbey church at Saint Germer-de-Fly (Oise) (cir. 1130-40). That this method was abandoned in most of the remaining Transitional churches would seem to have been due to the fact that the vaults of Saint Étienne at Beauvais fell in, and those of Saint Germer did not prove very secure.[187] Such builders as the Abbot Suger of Saint Denis, therefore, may very naturally have looked to Normandy for a method of vaulting, since the vaults of Saint Étienne at Caen had at least remained in place. Whatever the cause of its introduction into the Ile-de-France may have been, the six-part system was used at Saint Denis (Seine) (1140-1144) and soon became the favorite method throughout the neighboring region. Unfortunately Saint Denis and two other important churches of the Transition, the cathedrals of Senlis (Oise) (cir. 1150) and Noyon (Oise) (cir. 1140), which would undoubtedly have illustrated the progress in six-part vaulting, no longer have their original vaults, and the cathedral of Sens (Yonne) (1140-1168) (Fig. 28) remains as perhaps the most important example of the early developed type.[188] Its vaults show the great advance made in construction since the completion of Saint Étienne at Caen. The diagonals are semicircular instead of segmental arches, and the transverse ribs are pointed and all of similar curve, giving a more symmetrical appearance and greatly reducing the thrusts. Furthermore the piers are profiled from the ground according to the load which they are to carry, and, last of all, a highly stilted wall rib is added over each clerestory window, completing the skeleton of the vault and making possible a larger expanse of glass and more satisfactory illumination for the interior. Of course, the use of the flying buttress, which had been introduced a short time before Sens was built, contributed enormously to the advancement of vault construction and in large measure explains such an improved form of vaulting as this is. In fact, a heavy clerestory wall was no longer essential to the support of the vault and it was only the fact that a large expanse of glass was not safe from the pressure of the wind, which prevented the clerestory windows from occupying the entire space beneath the formeret. With the invention of tracery, what little wall remained, was to disappear. A further advance is shown in the decidedly stilted form of the wall ribs, which (Fig. 28) concentrate all the thrust of the vault upon a very narrow strip of exterior wall where it was admirably met by the flying-buttress.[189] In fact, the system at Sens might be considered perfected were it not for the unnecessary size of the ribs, especially those running transversely. It remained for the builders of the cathedral of Notre Dame at Paris (begun 1163) to reduce all the ribs to the same size, and for the builders of the cathedral of Bourges (Cher) (begun 1172), still further to reduce all but the transverse arches and to employ the vault upon a scale even greater than that of Paris. In fact, Bourges marks the high water mark of this system of vaulting and by the beginning of the thirteenth century it was in general, entirely given up[190] in favor of the four-part cross-ribbed vault of rectangular plan, which regained its supremacy in the Ile-de-France after the introduction of the flying-buttress with the protection which this afforded against such a catastrophe as that which probably befell Saint Étienne at Beauvais. Although employed to a much greater extent in France[191] than elsewhere, almost every country in Europe possesses a number of churches with six-part vaults. Thus William of Sens introduced the system into England, where it appears in Canterbury cathedral choir (1175) and later in Lincoln transept[192] (cir. 1215). Italy possesses many examples, among them the large churches of San Francesco at Bologna (cir. 1240), the Certosa of Pavia (1396), and the small church of Corneto-Tarquinia (Roma)[193] where the vault curiously enough appears over two bays of rectangular plan which divide what would otherwise be practically a single square nave bay.[194] Examples in other countries might be cited, but in no case would they differ materially from the French prototypes. Variants of Sexpartite Vaulting The fact that six-part vaulting declined rapidly in favor toward the beginning of the thirteenth century, and thus before the era of complicated vaults had begun, probably explains the few variants from the standard type. Of these, the simplest consists in the addition of a ridge rib along the longitudinal vault crown. This appears in one bay of the choir of Lincoln cathedral[195] (Fig. 35), where the crown line is horizontal, and in the great transept of the same church where it rises and falls in accordance with the doming up of the central keystone. The small church of Saint Jacques at Reims (Marne) (1183) (Fig. 29) presents a still better example of this irregular ridge rib. The vault of Saint Jacques would seem from its general appearance to be based upon Anjou models and it is not surprising to find its possible prototype in the church of La TrinitÉ at Angers (Fig. 30). The reason for the employment of the extra rib is probably twofold: first, to lessen the size of the transverse panels; and second, to render the arrangement of the ribs and severies more symmetrical. In England, it is quite possible that it served as a cover-joint as well, but in France this would not seem to hold true, at least in La TrinitÉ, where the stone courses are laid with as much care as those in the simple four-part vaults of Angers cathedral (see Fig. 19). La TrinitÉ at Angers (Fig. 30) is also an important variant of the six-part vault because the impost of its intermediate rib is raised to a considerably higher level than that of the principal transverse arches and the intermediate rib itself is highly stilted. This would seem further evidence that the six-part vault was evolved from the four-part vault in an effort to make the arrangement of the windows more symmetrical in a single nave bay corresponding to two bays in the aisles;[196] for if La TrinitÉ with its series of side chapels, two to each nave bay, had been vaulted in the usual Anjou style and the windows left as they now stand on the axis of each chapel arch, their heads would either have been cut by the wall line of a four-part vault or would have appeared awkwardly placed beneath it. The addition of an intermediate transverse arch and the conversion of the vault into sexpartite form restored the symmetry of piers, arches, and windows. In order, however, to obtain as much light as possible and to produce the effect of square nave bays, these intermediate transverse ribs were stilted and their imposts raised. Nor was this stilting confined to Anjou. It appears a number of times elsewhere often in churches where the ridge rib was not employed for example, in the cathedrals of Bremen and Limburg[197] in Germany, and in those of Ribe,[198] and Viborg in Denmark.[199]
The church of the Certosa of Pavia in Italy (1396) has six-part vaults of similar type but presents a curious arrangement of square nave bays corresponding to rectangular bays in the side aisles (Plate I-d.).[200] The intermediate transverse arches, therefore, rise from corbels above the crowns of the side aisle arches, a fact which explains their higher imposts. Why such a vault should have been used can again be explained by the desire to obtain the best possible arrangement of windows. Five-part vaults had already been used in the aisles of the Certosa to get square flanking chapels, and it was natural that the builders should have wished to have a clerestory window corresponding to each exterior bay of the church. The fact that square nave and rectangular aisle bays were used at all would seem to have been due to the Italian fondness for this system which caused the least possible obstruction of the church interior by piers. The only curious feature is, therefore, the use of the six-part, instead of the more natural four-part, vault. A somewhat similar arrangement with the substitution of two four-part vaults for the six-part vaults of Pavia is to be seen in the cathedral of Magdeburg,[201] where the same combination of nave and aisle bays occurs. The builders, like those of Pavia, first subdivided the outer longitudinal cells of the side aisle vaults by a half rib in order to obtain two windows instead of one, which would necessarily be of rather clumsy shape or of small size were it placed below the long, low wall rib of a simple rectangular four-part vault. Then to make the nave bays and clerestory windows correspond to those of the aisles in exterior elevation, as well as to obtain better window space, they constructed two rectangular four-part vaults over each square nave bay with their intermediate transverse rib resting on corbels above the aisle arches (Plate I-e.). Eight-Part Vaulting There is one more important variant of the six-part vault which is especially interesting and unusual. It appears in the church of Saint Quiriace at Provins (Seine-et-Marne) (cir. 1160) (Fig. 31)[202] and consists in a division of the nave into great square bays each corresponding, not to two, but to three square bays in the side aisle (Plate I-f.). The divisions thus formed are covered by what is really an eight-part vault, which is precisely like six-part vaulting except that there are three instead of two window cells in either side of each bay. Needless to say the immense size of the transverse triangular severies thus created presented a structural problem of much difficulty, and it is not surprising that such a vault was but seldom imitated,[203] particularly as the great discrepancy in the size of the vault cells and the awkward angles formed by their crowns give a decidedly unpleasant appearance. Nevertheless, there is one instance, at least, in which this system was not only imitated but transformed into a ten-part vault. This was at Boppart, Germany,[204] where the thirteenth century church has vaults with four window cells and but a single pair of diagonals. To break up the two remaining triangular severies, added surface ribs were introduced (Plate I-g.). Rectangular Nave Bays with Four-Part Cross-Ribbed Vaults While the builders of Normandy were developing the sexpartite system just discussed, those of the Ile-de-France were experimenting with the simple four-part cross-ribbed vault of rectangular plan (Plate I-h.). As in Normandy, the earliest churches of the province were in the main wooden roofed basilicas like the Basse-Oeuvre at Beauvais. When groined vaults first appeared in the Romanesque period, they were generally employed only in the side aisles, as at Morienval,[205] and if one may judge from these vaults, which have unfortunately been rebuilt, they were of slightly domed up section somewhat like those of Lombardy and the Rhenish provinces. Toward the beginning of the twelfth century, however, when the central power had been greatly strengthened under Louis VI. (1108-1137), there began a marked architectural advance which was destined to render this backward province the most important of all in the development of Gothic architecture. One of the earliest churches to mark this advance was Saint Étienne at Beauvais (probably early twelfth century) (Fig. 32), which, if one may judge from the form of the piers and the ribbed vault of the side aisles,[206] was planned from the foundation for vaulting throughout. Unfortunately the original vaults of the nave, if such existed, are no longer in position for they either gave way from lack of support, a natural supposition since they had no other abutment than the weight of the clerestory walls, or else they were so injured by the fire of 1180 that it was necessary to replace them by the existing vaults of the late twelfth century. These, while they do not make up for the loss of their predecessors, are nevertheless important because of their early date. They are antedated, however, by a number of very important churches which still retain, in part at least, their original vaulting. Fig. 32.—Beauvais, Saint Étienne. Irregular Four-Part Vaulting of Durham Cathedral The first of these is the English cathedral of Durham. The date of its vaults is still the subject of a decided controversy, but whether they were built between 1093 and 1133 as Bond,[207] Rivoira,[208] and Moore[209] believe, or are later than those of Saint Denis, which is the claim of Lasteyrie,[210] they are of sufficiently early date to be important in a discussion of rectangular four-part vaulting. Those over the nave (Fig. 33) are especially interesting and furnish a unique variant of the standard type. It was the apparent intention of the builders to roof the nave with wood and for this purpose heavy transverse arches were constructed between the alternate piers. When vaulting was determined upon, the nave was therefore already divided into square bays each containing two clerestory windows on a side. To vault these bays the builders might naturally have been expected to adopt the Lombard system of simple four-part vaults, but here in Durham, as in Saint Étienne at Caen, the impost level of the transverse arches was so low that a four-part vault would have made impossible the retention of the windows already in position above each nave arch. As these were absolutely essential in the north of England for lighting purposes, and also most important in preserving the symmetry of the bays, a change either in their size or position would have proved impractical. The six-part vault was the Norman method of solving a similar problem. But the builders of Durham invented a new system, made up of two rectangular cross-ribbed vaults in each bay, their intermediate supports afforded by corbels, and their alternate transverse arches omitted (Plate I-i.). This omission of the intermediate rib gives a very unusual character to the vault but it preserves the alternate system with square nave bays so popular in Norman work, and at the same time has a great advantage over the six-part vault in that the transverse crown line of the window cells is perpendicular to the outer wall. The panels are therefore more symmetrical in elevation and the thrusts are more evenly distributed from pier to pier. The large central severy, however, afforded a difficult surface both for construction and support, and it is not surprising that the system was not repeated. As in the early ribbed vaults at Caen, wall ribs were not employed at Durham, and the abutment was provided only by flat pilasters and concealed flying buttresses, some of full and some of half arched form.[211] Early Four-Part Ribbed Vaults in Normandy That the rectangular four-part system of vaulting was developed in Normandy, as well as in England and the Ile-de-France, and very possibly independently of both, is proved by the early twelfth century abbey church of Lessay (Manche) (cir. 1130).[212] If the vaults of Lessay are an independent development it is hardly possible to see in them anything else than another effort to vault a church with square nave bays and yet provide the best possible vaulting to fit above the windows. A glance at the choir[213] will show that the alternate system was here employed just as in Saint Étienne at Caen, yet the builders introduced two four-part vaults instead of one of six-part type in each bay.[214] The transverse arches are still semicircular and the vault is somewhat rudimentary. The system as a whole may be considered as a fourth method[215] of the Norman builders to preserve their clerestory intact and still vault their churches. A slight advance is shown in the vaults at Pontorson (Manche) (middle of twelfth century). This is, however, a small church without side aisles and its vaults are in almost square bays with pointed transverse arches and considerably domed up at the crown. Wall ribs are still lacking as at Durham and Lessay. Transitional Four-Part Ribbed Vaults in the Ile-de-France The abbey church of Saint Germer-de-Fly (Oise) (cir. 1140), which still retains its original vaults in the choir and two eastern bays of the nave, presents another and perhaps more important example of rectangular four-part cross-ribbed vaulting. Its structural arches are of pointed section, and the piers and walls are strengthened by concealed flying-buttresses beneath the wooden roof of the triforium.[216] These are similar to those which have already been noted in La TrinitÉ at Caen and in the nave of Durham,[217] but the vaults are superior in construction to those at Durham and are also provided with transverse arches between each rectangular bay. With the aid of this concealed buttress and the retention of the heavy Romanesque walls and small openings the vaults of Saint Germer were kept from falling, and it was doubtless this fact which led to the extension of the four-part system until it rivaled and at length became more popular than the six-part vaulting imported from Normandy and used at exactly the same period in the church of Saint Denis. A number of elementary features still remained at St. Germer, however. The transverse arches are but slightly pointed in section, the ribs are unusually heavy, and the diagonals of the choir bay are supported upon corbels[218] showing that the shaft arrangement was not yet in accord with the ribs to be carried. A gradual development of the flying-buttress, and of the compound pier, a reduction in the size of the ribs,[219] and many other structural refinements rapidly followed one another in the period subsequent to the construction of Saint Germer and led to the perfection of rectangular four-part vaulting. The cathedral of Soissons (Aisne) (cir. 1212 on) (Fig. 67), for example, shows a considerable structural advance over Saint Germer. Its ribs are more decidedly pointed though still somewhat heavy and there is no hesitation in raising the impost of the vault far above the clerestory string-course, since its thrusts are easily met by exterior flying-buttresses. Developed Four-Part Ribbed Vaults It is in the cathedral of Amiens (beg. 1218) (Fig. 69), however, that the four-part vault reaches its most daring if not its most perfect form. Here the builders constructed a vault similar to that of Soissons, but rising over one hundred and forty feet from the pavement. Its ribs are perfectly proportioned and finely moulded and the buttress system is completely developed. One awkward feature does, however, appear in the fact that the builders, perhaps, in order to concentrate the thrusts of the vaults upon the narrowest possible strip of outer wall, have made the wall intersection of the window severies follow an irregular curve which does not correspond to that of the wall rib in the portion from the impost to a point near the haunch. In spite of this defect, the cathedral of Amiens may well be considered as marking the highest development of rectangular ribbed vaulting. A study of other Gothic churches will disclose few, if any, improvements, either in appearance or construction, and many of the finest closely resemble this masterpiece. The Curve of Vault Ribs Such a study will, however, show a decided difference in the elevation of the transverse ribs and consequent shape of the vaults, which is worthy of some notice. If, for example, a triangle be inscribed beneath a number of these transverse arches, it will be found that the angles inside its base vary from about fifty degrees in Saint Germer-de-Fly, Rouen cathedral and Beverley Minster;[220] to fifty-five degrees in Soissons, Amiens, Salisbury, and Milan cathedrals, and Westminster Abbey; and even to sixty degrees in the cathedrals of Cologne and Reims. Moreover there is a great difference in the curve of these same transverse ribs. Those in Saint Germer, Beverley, and Rouen closely approach a semicircle, those in Amiens and Salisbury are much more pointed, but made up of two arcs without, however, a long radius with the resulting flattened appearance to be noted at Cologne and Reims and more decidedly at Milan. All this would seem to indicate that the elevation of these ribbed vaults,—and this is true of six-part and complex vaults as well,—was largely a matter of individual taste with a tendency to favor the form used at Amiens. The reason for the employment of very sharp curves like those of Reims, Cologne and Milan, was doubtless due to the appreciation on the part of the builders of the fact that such curves greatly reduced the outward thrusts, rather than to any idea of beauty of appearance to be gained, for in this they are perhaps inferior to the less pointed examples. Rectangular Four-Part Ribbed Vaults in Churches without Side Aisles
The use of rectangular four-part ribbed vaulting was not confined to churches with side aisles, but appears also in those with a single broad nave. It is the method employed in the Sainte Chapelle at Paris (fin. 1248), where there are simple salient buttresses, and there is a splendid example in the Cathedral of Albi (Tarn) (begun 1282) (Fig. 34), where the nave has a very wide span and is flanked by chapels in two stories between heavy pier buttresses which are thus enclosed in the church in a truly Byzantine manner. In the smaller church of Saint Nicholas at Toulouse these buttress chapels are in but one story and the bays are more nearly square in plan, a compromise between the square and rectangular systems which appears on an even larger scale in the cathedral of Saint Bertrand-des-Comminges (Haute-Garonne) (cir. 1304). As far as construction is concerned these vaults over a single broad nave offer no advance over those in churches with side aisles, not even requiring a scientific system of flying buttresses to offset their outward thrust. Their only importance lies in the very broad space sometimes covered by them.[221] Vaulting with Added Ribs The simple forms of ribbed vaulting just discussed were the ones most frequently in use during the best Gothic period. But among certain builders, there was a tendency even in the thirteenth century to introduce additional ribs into the vaults, a custom which later gave rise to a vast number of complicated vaulting systems especially in England, Spain and Germany. Even to enumerate these would be almost impossible and a description of each is out of the question, hence only those combinations which were frequently employed, or which gave rise to new types, will be discussed. Origin and Use of the Ridge Rib Naturally enough the ridge rib was the first to be added to those already constituting the four-part vault (Plate I-j.). But the vaults thus formed should be divided into two groups. The first most frequently found in France and already discussed in connection with the churches of Anjou,[222] is that in which the surface of each severy has a curved crown and the rib follows this curve, with the object, probably, both of subdividing the large rectangular bays, of marking with absolute exactness the crown line, and of aiding in rigidly fixing the central keystone, or even in the case of a six-part vault, of giving the same apparent division to the transverse severies as is found in those running longitudinally. Though very similar to this first type, the second, which was developed and most used in England, is different, in that the ridge line is here perfectly horizontal, and the main purpose of the rib is to mark this horizontal line with absolute exactness and to give, what Bond terms a spine,[223] to the vault skeleton. In the earliest example in England, the transept aisle of Ripon cathedral (cir. 1170),[224] the ribs are so small as to be purely decorative. This leaves the choir of Lincoln cathedral (begun 1192) (Fig. 35) as the first English example of importance in which a true ridge rib appears. It is not yet absolutely horizontal since there is a slight curve to each severy. Its presence would seem to be due to the peculiar form of the vault, in which the ribs enclosing the window cells do not meet at a common point of intersection but at two points somewhat distant from each other along the ridge line where each pair is abutted by a single rib running to the nearest impost on the opposite wall (Plate I-l.). This arrangement, which was probably planned to increase the amount of centering in the large transverse panels and thus render their construction easier,[225] gives an extra keystone in each bay and it is quite possible that the ridge rib was introduced in order to unite these intersections and fix them in a straight line. It does not appear in the window cells where it would of course have been at an awkward angle with the outer walls. Once introduced into English architecture the ridge rib was destined to play a most important part in its development. In the first place, it provided an easy method of assuring an absolutely level and straight ridge line and was thus especially welcome to English builders, who had been trained in the construction of vaults which were never more than slightly and often not at all domed up, and who were, besides, rather inferior masons, and not particularly skillful in making their masonry courses intersect in a perfect manner. In the second place, it furnished admirable abutment for tiercerons or intermediate ribs,[226] which were perhaps suggested by such a vault as Lincoln choir as being valuable additions to the rib skeleton and were thereafter very generally used to provide more permanent centering and to further reduce the size of the vault panels. It is, however, notable that a longitudinal ridge rib appears added to simple four-part vaults without the introduction of tiercerons or transverse ridge ribs at a comparatively early date in Worcester cathedral choir (after 1224),[227] Westminster Abbey choir (1245-1260), and Gloucester cathedral nave (1245), and that it is used in France in a number of churches where there are no tiercerons.[228] In such cases it serves the primary purpose of clearly marking the ridge line, which is especially difficult to adjust in vaults with level crowns. That it was the longitudinal effect thus produced which was desired is evidenced by the fact that except when there were tiercerons in the longitudinal cells, the transverse ridge rib was rarely added to such vaults (Plate I-k.). Among the very few examples are the cathedral of Tulle (CorrÈze) (twelfth century) and the fifteenth century chapel of the chÂteau at Blois, both of them in France. [229] Tierceron Vaulting The introduction of a ridge rib was only the first step in the development of multiple rib vaulting. It was not long before the builders, especially in England, began to add intermediate ribs or tiercerons between the transverse arches and the diagonals. These may possibly have been inspired by the extra ribs in the choir of Lincoln cathedral (Fig. 35 and Plate I-l), but whatever their origin they became a common feature of later Gothic and gave rise to what may be termed tierceron vaulting. In the transverse vault severies, which in England were really sections of a tunnel vault because of the level crown line, these ribs acted largely as added centering and as decorative features. But when used in the window cells they served another purpose as well for they enabled the builders to convert the ordinary “ploughshare” curve of the vaulting conoid into a series of flat panels which could be constructed with much less difficulty as far as the laying of the masonry courses was concerned. Sometimes the tiercerons are used in both the transverse and the longitudinal severies and sometimes only in one of them. Their number also varies greatly, though of course they are always in pairs. Lincoln cathedral presbytery (cir. 1266-1280) (Fig. 36) affords an example of a single pair in each of the large transverse severies with none in the window cells (Plate I-m.), while Chester cathedral chapter-house (first half of the thirteenth century), and Worcester cathedral nave (cir. 1350-1377) (Fig. 89) are rare examples of the opposite arrangement (Plate I-n.).[230] To support such tiercerons as these at their crown, a transverse ridge rib was added to the construction, sometimes as in Chester chapter-house (Plate I-n.), Lincoln nave (before 1233),[231] and Ely presbytery (1235-1252),[232] running out only to the new keystone (Plate I-o.) and thus playing a purely structural rÔle, but often extending to the window head (Plate I-p.) as in Lichfield cathedral south transept (cir. 1220) and choir (fourteenth century). These portions of Lichfield, together with the nave of Lincoln and the presbytery of Ely cathedral, are also important as showing the employment of a single pair of tiercerons in each of the four panels of the vaulting bays (Plate I-p.). This system is slightly varied in the naves of Lichfield and Hereford (Plate I-q-r), where the true transverse arch is omitted between the bays, but these vaults like those of Durham are merely variants of the more standard types.[233] The introduction of a single pair of tiercerons in each major panel was soon followed, especially in the window cells where the surface was warped, by the use of two (Plate I-s.) and even of three such pairs (Plate I-t.). Two are found in Hereford cathedral south transept (cir. 1400),[234] and in the choir of Saint Mary Redcliffe at Bristol (fifteenth century),[235] while three appear at Exeter (between 1280-1350) (Fig. 37). This last may well be said to mark the highest point in tierceron vaulting,[236] and it must be acknowledged that the decorative effect produced is most pleasing. Placed as they are over comparatively low naves, these vaults harmonize in an admirable manner with the clustered piers, moulded archivolts, and substantial walls provided for their support, and carry to the crown of the vault that wealth of moulding which lends so much of grace and charm to the English Gothic of the Decorated period. Were such vaults used above the lofty naves of Amiens or Beauvais, they would doubtless appear oppressively heavy but the lowness and solidity of English construction entirely dispels such a feeling. Of course, tiercerons are not essential members of the vaulting system and perhaps they were better omitted altogether, but that their usage can be vindicated from an aesthetic standpoint is proved by such vaults as those at Exeter.
Lierne Vaulting Tierceron vaulting did not, however, mark the limit to which the English Gothic builders were to carry their passion for added ribs and complex design, and it was not long before short connecting ribs known as liernes were added to the tierceron vaults. These may have been introduced by the builders from a feeling that the tiercerons did not have sufficient abutment, as Bond suggests,[237] but it is more reasonable to suppose that they are the result of a striving for still more complex vaulting forms and still more decorative patterns in vault construction. The combinations in lierne vaulting are of course without number and only a few can be discussed. The simplest is that known as the star vault (Plate I-u.) in which there is a single pair of tiercerons in each of the four main vault panels with short liernes connecting the points of their intersection with the ridge ribs, with a point in the same plane on each of the diagonals. A simple example occurs at Oxford in the Proscholium[238] and one of the same general type but much elaborated, in the choir of Oxford cathedral.[239] It is almost impossible to classify the remaining lierne vaults under separate heads, though there are certain characteristics which belong to one group and not to another. For example, some, like those of the nave of Saint Mary Redcliffe at Bristol[240] have no ridge rib, others have a single rib like that found in tierceron vaulting. These last might again be classified according to the number and arrangement of their liernes. Thus in Ely cathedral choir[241] (beg. 1322) and Norwich nave (vaults cir. 1470)[242] there are but few liernes, while in Winchester cathedral nave (cir. 1394-1460) there is a much larger number. Still other lierne vaults have more than one ridge rib. Of these, the choir (1337-1357), and Lady chapel of Gloucester cathedral (cir. 1457-1489), and the nave of Tewkesbury Abbey (Fig. 38)[243] are representative and varied examples. All have three ridge ribs which is the standard number. Interpenetrating Multiple Ribbed Vaults In these last three churches, however, as well as in Winchester nave and in numerous other examples not cited, there is a still more decided change in the form of the vault than that brought about by the use of liernes or added ridge ribs. This lies in the fact that the window cells no longer rise to the full height of the vault, so that the entire system is practically a reversion to the Romanesque tunnel vault pierced on either side with lunettes, in other words, to the interpenetrating vault. The ribs merely form a permanent centering, and generally no attempt is made to concentrate the pressure on a narrow strip of wall,[244] or to make use of flying-buttresses.[245] Except for the decoration which they afford, the ribs have little structural value though they do make possible lighter masonry in the web than would be possible in a continuous tunnel vault. The height of the window cells in such vaults was not at all fixed though it was quite frequently determined by the intersection of two ribs running diagonally from each side of the window to the second impost on the opposite wall of the church.[246] Such window cells as these naturally left a large central space along the crown of the vault, which was usually decorated by extra lierne and ridge ribs. Tracery Vaults Not content with the liernes as a decoration, an innovation appears in Tewkesbury choir,[247] Saint George’s Chapel at Windsor[248] and elsewhere, which consists in the application of raised mouldings forming tracery patterns on the few open spaces left between the ribs of complex lierne vaults. It is as if the tracery of a window were applied to a background of stone, with ribs taking the place of mullions. The patterns are usually trefoils or quatrefoils, but other forms, as, for example, the cross shaped flowers in the fan vaults at Peterborough (Fig. 39) also occur. The natural consequence of such added mouldings and ribs as those just described was to bring about the total sacrifice of the structural principles of ribbed vaulting to those which were purely decorative, and it is not surprising that such a vault as that of the choir of Wells cathedral (1329-1363),[249] in which the ribs have but the slightest claim to structural purpose should be found even at its early date as an example of this decadent stage in English vaulting. Fan Vaulting But the addition of multiple ribs lead not only to such debased vaulting as that at Wells. It must have played a large part in the creation of the distinctly novel construction known as fan vaulting. For in a vault with many tiercerons, as for example, that at Exeter (Fig. 37), or Hereford south transept,[250] the combined surfaces between the ribs is a cross between half of a hollow sided pyramid and a cone. This is true because, like most of the English churches, the wall rib is not highly stilted to concentrate pressures on a narrow strip of outer wall, or to leave a more pointed window head as in France, but it and the tiercerons and diagonals have much the same curvature. It was natural, therefore, that the English builders should have conceived the idea of making all the ribs of just the same curvature but of different length according to their several positions. This they did in Sherborne Abbey nave (vaulted 1475-1504).[251] Here the builders very logically used the shortest rib as a measure and connected the points at corresponding distances from the imposts on each rib with liernes. A central space was thus left, which at Sherborne was covered by prolonging a number of the radiants and adding a tracery of liernes and mouldings. The vault as thus constituted is not yet of pure fan type. It was first necessary to replace the ring of straight liernes by those of curved plan and to add one ring above another at the various points of intersection of the tiercerons and transverse ridge ribs, until practically the entire space to the vault crown was filled. Thus, in certain of the fan vaults of Peterborough (second half of the fifteenth century) (Fig. 39), there are three such rings leaving but a small diamond shaped central space which is largely filled by the keystone of the bay.[252] Others down the side aisles where the bays are smaller have but a single ring and a much larger central space. In vaults of the Peterborough type, the radiants are continued through this central panel in a decorative way, but in the cloister at Gloucester (before 1412) (Fig. 40), this portion of the vault is left entirely flat and decorated with tracery patterns in raised mouldings such as are usually found in window heads. The conoids, also, are covered with tracery rather than continuous ribs and the term “Fan-Tracery Vaults” might properly be used to distinguish them from the more common type.[253] In the matter of construction, fan vaulting differs from any preceding method. Its ribs are all of precisely the same curvature, their length being determined by the position which they occupy, and they are no longer supporting but rather decorative members. The lower portions of some of the vaults still resemble true ribbed vaulting in that the tas-de-charge is used, and also in the fact that the ribs still rise in a single long voussoir from their imposts to the first horizontal ring. But from this point to the crown, the ribs and mouldings are merely carved in relief upon the jointed masonry, which they therefore in no way support. In some fan vaults, as, for example, in Islip’s chapel in Westminster Abbey,[254] and in Gloucester cathedral cloister (Fig. 40), the rib is even carved upon the vault masonry for its entire length. The one structural advantage which the fan vault afforded lay in the fact that it could be built up of practically horizontal courses in a manner to exert very little outward thrust; while the substitution of curved, for straight liernes did away with the awkward angular intersections characteristic of lierne vaulting. Altogether, it is both a clever and beautiful type of vaulting well suited to the builders of the Perpendicular Gothic period, with their fondness for intricate decorative rather than structural problems. Pendants Because of its late development, fan vaulting was not extensively used to cover an entire church. Nevertheless, King’s College Chapel at Cambridge (vaulted between 1512 and 1515),[255] and Bath Abbey (cir. 1500-1540),[256] furnish two excellent examples, to which might be added Henry VII’s Chapel at Westminster (cir. 1500-1520).[257] The latter is essentially of fan type, though the fans are in combination with a system of transverse arches and pendants best understood from the photograph and drawing just cited. The vaults in the foregoing churches, do however exhibit minor differences. For example, the transverse arches are practically concealed in the vaults of the naves at Sherborne, and Bath and in the east aisle of Peterborough, while they are prominent in Henry VII’s and King’s College chapels. Moreover, in a number of fan vaults as well as in others of different type, pendant voussoirs or keystones are employed. These are supported by some clever building trick and beautifully carved either as lanterns or reliquaries,—like those of Oxford cathedral choir,[258]—or decorated with rich floral, heraldic, or other designs. Thus they play a rÔle which is largely decorative, though one which also marks a very clever building technique.[259] Vaults with Added Ribs—Outside of England The vaults thus far discussed have been largely those of England, but some of the types with added ribs, most highly developed in that country were not without Continental examples. In France, for instance, ridge ribs, besides being used in vaults of the domed up Anjou type already described, are also found marking level ridges like those of the standard English vaults. The nave of the abbey church of Souvigny (Allier) (late fifteenth century), the north transept of the cathedral of LeMans (before 1430), and the chapel of the Maison de Jacques Coeur at Bourges (middle of fifteenth century) afford excellent examples of the use of the longitudinal without the transverse ridge rib, while the chapel of the chÂteau of Blois, and the cathedral of Tulle (CorrÈze), have already been cited as rare instances in which both were employed in vaults with level crowns. That the French builders were even more impressed with the decorative possibilities which these ribs afforded than were those of England is perhaps shown by the fact that, whereas in England this rib has carved decoration[260] only rarely as in the nave of Lichfield cathedral it is carved in no less than three of the French examples cited, the chief among these being Souvigny, in which a deeply cut foliate design decorates both sides of the rib throughout its entire length. In Spain also there is a notable example of the decoration of both a longitudinal and transverse ridge rib in the form of a knotted rope or scourge in the cathedral of Vizeu.[261] Tiercerons as well as ridge ribs were freely used on the continent though usually not at a very early date. Fine examples are to be seen in France in such churches as those of Brou (Ain) (1506-1536), and Saint Nicolas-du-Port (Meurthe-et-Moselle) (cir. 1505).[262] Both of these are also of interest because their vaults still retain the domed up crown characteristic of French construction, and because of this the builders, to avoid the awkward rise and fall of continuous ridge ribs, have brought these out only far enough to meet the pair of tiercerons in each severy. Many other examples of tierceron vaulting could be cited both in France and elsewhere, but they would add nothing of importance from a structural standpoint. As for lierne vaults, they, too, appear on the Continent especially in Germany and Spain. The choir of Freiburg cathedral (second half of fifteenth century) (Fig. 72), and the church of the Holy Cross at Gmund,[263] show two German types, both of which resemble English vaults which have already been discussed. In Spain, the new cathedral at Salamanca[264] (begun 1513), the cathedral at Segovia (begun 1525),[265] and many other churches might be cited, while in France the church of MÉziÈres (begun 1499),[266] and Switzerland the cathedral of Bern (cir. 1421-1598)[267] show the extent of the style, sometimes with sharply defined domed up bays as in MÉziÈres and sometimes a continuous vault like that of Bern. Finally in some instances, as, for example, the Stadkirche of Wimpfen[268] the liernes are curved giving a still more complicated character to the vault. Fan vaulting was unused[269] outside of Great Britain, but there are many instances of the employment of extensively decorated vaults, including those with pendants of somewhat English character. Among the latter are Saint Pierre at Caen and Saint Eustache at Paris (1532-1637),[270] while pendants of especially exaggerated type are to be seen in the vault of one of the chapels off the south side aisle of Noyon Fig. 41.—Noyon, Cathedral, Chapel. cathedral (Fig. 41). A tendency to decorate the panels is also noticeable in a number of late French vaults, as for example that of the chapel of Saint Jacques at ClÉry (Loiret) (probably after 1485) (Fig. 42), where each of the larger divisions of a complicated lierne and tierceron vault is decorated by a wallet and staff or a scourge in low relief. At Rue (Somme), in the chapel of Saint Esprit,[271] there is a somewhat similar vault with heraldic devices and floral ornament on the panels. But even more notable are the angels in the round which have been added for decorative purposes in four of the severies of the vaults in one bay of the side aisle of the north transept (sixteenth century) in Senlis (Oise) cathedral (Fig. 43). The final stage in elaborate vaulting, is perhaps, to be seen in such a vault as that of the Chapelle de la ViÈrge at La FertÉ-Bernard (Sarthe)[272] which dates from 1535-1544. Here the panels are merely portions of a flat ceiling resting upon a series of arches arranged like ribs, but carrying a tracery framework upon which the elaborately decorated ceiling with its mouldings and stalactite pendants is made to rest. Side Aisle Vaulting There now remain for consideration before closing this chapter, the ribbed vaults of the aisles and triforia of Gothic churches. Very naturally the general development of ribbed vaulting in the aisles closely parallels that in the nave. In by far the larger number of churches, the side aisle bays are square and covered with simple four-part cross-ribbed vaults. As in the case of the nave, those of early date have many clumsy features. Thus in the aisles of Saint Étienne at Beauvais (Fig. 44)—which, fortunately, retain a few bays of their primitive vaults dating from about 1125—the diagonals are heavy (cir. 20-25 cm. thick)[273] and either square with simple bevelled edges or of single torus section. No wall rib is found and the transverse arches, besides being very thick, are of round-headed form, highly stilted to bring them up to approximately the general vault level. The vault itself is slightly domed up at the crown and besides the
primitive characteristics just enumerated, its panels are composed of small stones roughly joined and in very uneven courses, while the ribs themselves are built up of short voussoirs, which are not combined at their springing in the familiar tas-de-charge of more developed Gothic work. The cathedral of Sens presents in its side aisles (Fig. 45), which date from the twelfth century[274] a slightly different system. The transverse arches are still heavy and semicircular but they are not stilted. The diagonals rise from corner corbels—a fact which may prove that the aisles were originally planned for groined vaulting and thus no provision made for the cross-ribs,—and they are also semicircular, thus giving the vault a decidedly domed up character. This makes these vaults at Sens very similar to Lombard work and it would seem as though their builders had the same object of saving centering by the use of ribs as obtained in Lombardy. There is one apparent advance over those at Beauvais in the presence of a wall rib, but this is of too wide a span to fit under its severy, and it would seem to have been designed to mark the wall intersection of groined rather than ribbed vaulting. The early aisle vaults in England are generally similar to those at Beauvais, with even less doming or none at all. The earliest would seem to be those in Peterborough, Durham and the north nave aisle of Gloucester cathedrals, all dating, apparently, from before 1140. Although similar to those in Saint Étienne at Beauvais they differ in the comparative lowness of their transverse arches, which are but slightly stilted, and in the correspondingly reduced curve of the diagonals, which are less than semicircles and thus do not raise the crown of the vault. The explanation of this may very possibly be found in the desire of the builders to avoid cutting into the level of the triforium floor, especially at Peterborough, where this is a true gallery, and also in their familiarity with the flat crowned groined vault, which they had previously used in crypts and elsewhere. The form of the diagonals is in any case displeasing, as they spring from the shafts at an awkward angle and, furthermore, render the thrusts of the vault excessive.[275] Many structural refinements were, of course, necessary before these crude vaults gave rise to the fully developed type, but these refinements followed in general the same order as those in the larger nave vaults. First came the introduction of the pointed arch and its use for the transverse and longitudinal ribs in place of the semicircular type. This change may be seen in such early vaults as those of Noyon cathedral (cir. 1150) where pointed arches are used throughout. The noticeable feature here is the great size of the transverse ribs compared to that of the diagonals. This same feature continues to appear in a gradually lessening degree in many of the churches of the transitional period, and even in the developed Gothic of the thirteenth century, as, for example, in Bourges and Amiens cathedrals. This may, perhaps, be explained by the function of this transverse arch which was not merely a centering for the vault panel, but carried a considerable amount of the weight of the exterior buttress piers and wall pilasters which were connected above the aisle roofs by the arch of the flying buttress. These heavy transverse ribs also aided materially in bracing the nave piers and tying them to the outer walls. Sometimes, as in the beautiful aisles of Rouen cathedral, all the ribs are of the same section, but whether they were all the same or not, such vaults as those at Rouen and Amiens set the standard for developed Gothic side aisles. Five-Part Aisle Vaults
Other methods, however, were employed. Perhaps the chief among these is the five-part vault, in which the triangular severy nearest the outer wall in a four-part vault is subdivided by a half rib running to the main vault crown (Fig. 46). The advantage of such a system lies in the fact that it permits a more pleasing arrangement of windows in the outer wall, especially in bays of rectangular plan, like those in the Certosa at Pavia and Magdeburg cathedral already discussed, where the windows would otherwise fit but awkwardly beneath the broad low wall rib. The same system was also used in aisles with practically square bays, as, for example, in the cathedral of Coutances (Fig. 82), in Saint Urbain at Troyes and in many English churches.[276] Here, too, the explanation is to be found in the window arrangement, especially in the English and Norman Gothic examples, where these windows are of the slender lancet type, which could not be satisfactorily placed beneath the comparatively low wall rib of a square four-part vault. Multiple-Ribbed Aisle Vaults With the introduction of ridge ribs, tiercerons, and liernes, the side aisles show the same changes as those which took place in the nave. Simple ridge ribs appear, for example, in Lichfield cathedral, liernes at Worcester, while tierceron vaults could be cited in great number. Fan vaults, too, were used in the aisles, and have already been discussed in connection with those of the nave. Reconstructions sometimes produced an unusual vaulting system like that of Beauvais cathedral (cir. 1284), where transverse arches with tracery spandrels were added across each original aisle bay, giving the vault a pseudo-sexpartite character. True six-part vaulting was by its very nature ill-suited for use in the aisles and is very rarely found. There is an example, however, in Magdeburg cathedral.[277] A desire for novelty also seems to have been the cause of unusual vaults, such as those of Bristol cathedral choir aisles,[278] in which low transverse tracery arches separate the bays and carry a system of ribs which subdivide each bay into two rectangular four-part vaults running lengthwise of the aisle. Triforium Vaulting Although similar in plan to the side aisles, the triforia were apt to be a little later in being given ribbed vaults. In the abbey church of Saint Germer-de-Fly (Oise) (cir. 1140) and in the choir of La Madeleine at VÉzelay (Yonne) (cir. 1160 or 1170), for example, the triforium is not only left with groined vaults but is also constructed with round-headed arches, although both the ribbed vault and pointed arch are used in the aisles. This peculiarity may be due to the fact that groined vaults were easier and cheaper to construct over a low space like the gallery than a ribbed vault would have been, because they involved less careful stone cutting than was required for the ribs. Moreover, since the chief object of the transitional builders in using the ribbed vault would seem to have been to save centering, their object would not have been especially well served in the triforia, which were kept low to avoid detracting from the clerestory and therefore required but little centering compared to that which would have been needed for groined vaults in the side aisles. Another system with possibly a similar reason for its use appears in Mantes (Seine-et-Oise) cathedral (end of twelfth century), where the aisles are ribbed and surmounted by a triforium with transverse tunnel vaults, a most exceptional arrangement. It was only when the triforium began to play a larger rÔle in the church plan, when it was perhaps used for congregational purposes, that its vaulting began to develop like that of the aisles. Thus in the cathedral of Senlis (Oise) (cir. 1150) (Fig. 47), the triforium though comparatively low, is a veritable second story above the side aisles with its own good sized windows. Its vaults are still of rather primitive ribbed type. The transverse arches, though pointed, are heavy, and to avoid the flattened curve which the diagonals would otherwise have, the vault is given a domed up crown. The cathedral of Laon (Aisne) (cir. 1170) (Fig. 48) possesses a triforium of slightly greater height but still retaining excessively heavy ribs and domed up vaults. The triforia of the naves of Noyon (Oise) cathedral (cir. 1150-1180) and of Notre Dame at Chalons-sur-Marne (Marne) (1157-1183) show a gradual reduction in the size of these ribs, all of which finally become of practically equal section in the triforium of the cathedral of Notre Dame at Paris (beg. 1163), where the doming up of the crown also disappears to a large extent and where the gallery itself is nearly as lofty as the side aisles. After the beginning of the thirteenth century, triforia rapidly decline in popularity and are but rarely found except in Normandy, where there are beautiful examples in such churches as Saint Étienne at Caen choir rebuilt in the first quarter of the thirteenth century. Owing to its early decline in popularity, the triforium never presents those complex vaulting systems of the late Gothic period which have been described as appearing in the nave and aisles. Nave and Aisles of Equal Height In closing this chapter brief mention should be made of the series of churches in which the aisle vaults are nearly or quite as high as those of the nave, which they therefore aid in supporting. Among the numerous examples of such churches, the cathedral of Poitiers (Vienne) (cir. 1160 and thirteenth century) illustrates the type in which the vaults of the aisles are slightly lower than those of the nave, while Saint Serge at Angers has all the vaults at exactly the same level. Both are of Anjou type but this is due only to their geographical situation, for the system was widely extended.[279] In Germany there is a fine early example in Saint Elizabeth at Marburg (cir. 1235),[280] with vaulting of simple Gothic character, while the church of the Holy Cross at Gmund[281] is covered with vaulting of complex lierne type. Except for the change in interior elevation which the system brought about and the fact that it removed the necessity for flying-buttresses, it did not show any special progress along structural lines. It must be acknowledged that the churches thus constructed possess a most pleasing effect of spaciousness in their interior elevation, though this is offset by the lack of direct light in the nave. A final example of a church similar to those mentioned above but with a new vaulting system is afforded by Saint Florentin at Amboise (Indre-et-Loire) (fifteenth-sixteenth century). Its aisles are very narrow and are covered by transverse tunnel vaults in much the same manner as a number of Romanesque churches already discussed, except that the nave is here roofed with a ribbed vault. It is but a variant of the standard vaulting types described in this chapter.
|
