The Romans, in their arched constructions, habitually strengthened the
point against which the vault thrust by adding columnar features to
the walls, as shown in Fig. 108; thus again making a false use of the
column in a way in which it was never contemplated by those who
originally developed its form. In Romanesque architecture the column
was no longer used for this purpose; its place was taken by a flat
pilaster-like projection of the wall (plan and section, Fig. 109),
which gave sufficient strength for the not very ambitious vaulted
roofs of this period, where often in fact only the aisles were
vaulted, and the center compartment covered with a wooden roof. At
first this pilaster-like form bore a reminiscence of a classic capital
as its termination; a moulded capping under the eaves of the building.
Next this capping was almost insensibly dropped, and the buttress
became a mere flat strip of wall. As the vaulting became bolder and
more ambitious, the buttress had to be made more massive and of
greater projection, to afford sufficient abutment to the vault, more
especially toward the lower part, where the thrust of the roof is
carried to the ground. Hence arose the tendency to increase the
projection of the buttress gradually downward, and this was done by
successive slopes or "set-offs," as they are termed, which assisted
(whether intentionally or not in the first instance) in further aiding
the correct architectural expression of the buttress. Then the
vaulting of the center aisle was carried so high and treated in so
bold a manner, with a progressive diminution of the wall piers (as the
taste for large traceried windows developed more and more), that a
flying buttress (see section, Fig. 110) was necessary to take the
thrust across to the exterior buttresses, and these again, under this
additional stress, were further increased in projection, and were at
the same time made narrower (to allow for all the window space that
was wanted between them), until the result was that the masses of
wall, which in the Romanesque building were placed longitudinally and
parallel to the axis of the building, have all turned about (Fig. 110,
plan) and placed themselves with their edges to the building to resist
the thrust of the roofing. The same amount of wall is there as in the
Romanesque building, but it is arranged in quite a new manner, in
order to meet the new constructive conditions of the complete Gothic
building.
[Illustration: Figs. 108-114.]
It will be seen thus how completely this important and characteristic
feature of Gothic architecture, the buttress, is the outcome of
practical conditions of construction. It is treated decoratively, but
it is itself a necessary engineering expedient in the construction.
The application of the same principle, and its effect upon
architectural expression, may be seen in some other examples besides
that of the buttress in its usual shape and position. The whole
arrangement and disposition of an arched building is affected by the
necessity of providing counterforts to resist the thrust of arches.
The position of the central tower, for instance, in so many cathedrals
and churches, at the intersection of the nave and transepts, is not
only the result of a feeling for architectural effect and the
centralizing of the composition, it is the position in which also the
tower has the cross walls of nave and transepts abutting against it in
all four directions: if the tower is to be placed over the central
roof at all, it could only be over this point of the plan. In the
Norman buildings, which in some respects were finer constructions than
those of later Gothic, the desire to provide a firm abutment for the
arches carrying the tower had a most marked effect on the
architectural expression of the interior. At Tewkesbury, for instance,
while the lower piers are designed in the usual way toward the north
and south sides (viz., as portions of a pier of nearly square
proportion standing under the angle of the tower), in the east and
west direction the tower piers run out into great solid masses of
wall, in order to insure a sufficient abutment for the tower arches.
On the north and south sides the solid transept walls were available
immediately on the other side of the low arch of the side aisle, but
on the east and west sides there were only the nave and choir arcades
to take the thrust of the north and south tower arches, and so the
Normans took care to interpose a massive piece of wall between, in
order that the thrust of the tower arches might be neutralized before
it could operate against the less solid arcaded portions of the walls.
This expedient, this great mass of wall introduced solely for
constructive reasons, adds greatly to the grandeur of the interior
architectural effect. The true constructive and architectural
perception of the Normans in this treatment of the lower piers is
illustrated by the curious contrast presented at Salisbury. There the
tower piers are rather small, the style is later, and the massive
building of the Normans had given way to a more graceful but less
monumental manner of building. Still the abutment of the tower arches
was probably sufficient for the weight of the tower as at first built;
but when the lofty spire was put on the top of this, its vertical
weight, pressing upon the tower arches and increasing their horizontal
thrust, actually thrust the nave and choir arcades out of the
perpendicular toward the west and east respectively, and there they
are leaning at a very perceptible angle away from the center of the
church--the architectural expression, in a very significant form, of
the neglect of balance of mass in construction.
But while the buttress in Gothic architecture has been in process of
development, what has the vault been doing? We left it (Fig. 92) in
the condition of a round wagon vault, intersected by another similar
vault at right angles. By that method of treatment we got rid of the
continuous thrust on the walls. But there were many difficulties to be
faced in the construction of vaulting after this first step had been
taken, difficulties which arose chiefly from the rigid and
unmanageable proportions of the circular arch, and which could not be
even partially solved till the introduction of the pointed arch. The
pointed arch is the other most marked and characteristic feature of
Gothic architecture, and, like the buttress, it will be seen that it
arose entirely out of constructive difficulties.
These difficulties were of two kinds; the first arose from the
tendency of the round arch, when on a large scale and heavily
weighted, to sink at the crown if there is even any very slight
settlement of the abutments. If we turn again to diagram 77, and
observe the nearly vertical line formed there by the joints of the
keystone, and if we suppose the scale of that arch very much increased
without increasing the width of each voussoir, and suppose it built in
two or three rings one over the other (which is really the
constructive method of a Gothic arch), we shall see that these joints
in the uppermost portion of the arch must in that case become still
more nearly vertical; in other words, the voussoirs almost lose the
wedge shape which is necessary to keep them in their places, and a
very slight movement or settlement of the abutments is sufficient to
make the arch stones lose some of their grip on each other and sink
more or less, leaving the arch flat at the crown. There can be no
doubt that it was the observance of this partial failure of the round
arch (partly owing probably to their own careless way of preparing the
foundations for their piers--for the mediæval builders were very bad
engineers in that respect) which induced the builders of the early
transitional abbeys, such as Furness and Fountains and Kirkstall, to
build the large arches of the nave pointed, though they still retain
the circular-headed form for the smaller arches in the same buildings,
which were not so constructively important. This is one of the
constructive reasons which led to the adoption of the pointed arch in
mediæval architecture, and one which is easily stated and easily
understood. The other influence is one arising out of the lengthened
conflict with the practical difficulties of vaulting, and is a rather
more complicated matter, which we must now endeavor to follow out.
[Illustration: Figs. 93-107.]
Looking at Fig. 92, it will be seen that in addition to the
perspective sketch of the intersecting arches, there is drawn under it
a plan, which represents the four points of the abutment of the arches
(identified in plan and perspective sketch as A, B, C, D), and the
lines which are taken by the various arches shown by dotted lines.
Looking at the perspective sketch, it will be apparent that the
intersection of the two cross vaults produces two intersecting arches,
the upper line of which is shown in the perspective sketch (marked _e_
and _f_); underneath, this intersection of the two arches, which forms a
furrow in the upper side of the construction, forms an edge which
traverses the space occupied by the plan of the vaulting as two
oblique arches, running from A to C and from B to D on the plan.
Although these are only lines formed by the intersection of two cross
arches, still they make decided arches to the eye, and form prominent
lines in the system of vaulting; and in a later period of vaulting
they were treated as prominent lines and strongly emphasized by
mouldings; but in the Roman and early Romanesque vaults they were
simply left as edges, the eye being directed rather to the vaulting
surfaces than to the edges. The importance of this distinction between
the vaulting surfaces and their meeting edges or _groins_[2] will be
seen just now. The edges, nevertheless, as was observed, do form
arches, and we have therefore a system of cross arches (A B and C D[3]
Fig. 95), two wall arches (A, D and B C), and two oblique arches (A C
and B D), which divide the space into four equal triangular portions;
this kind of vaulting being hence called _quadripartite_ vaulting. In
this and the other diagrams of arches on this page, the cross arches
are all shown in positive lines, and the oblique arches in dotted
lines.
[Footnote 2: A _groin_ is the edge line formed by the meeting and
intersection of any two arched surfaces. When this edge line is
covered and emphasized by a band of moulded stones forming an
arch, as it were, on this edge, this is called a _groin rib_.]
[Footnote 3: The "D" seems to have been accidentally omitted in
this diagram; it is of course the fourth angle of the plan.]
We have here a system in which four semicircular arches of the width
of A B are combined with two oblique arches of the width of A C,
springing from the same level and supposed to rise to the same height.
But if we draw out the lines of these two arches in a comparative
elevation, so as to compare their curves together, we at once find we
are in a difficulty. The intersection of the two circular arches
produces an ellipse with a very flat crown, and very liable to fail.
If we attempt to make the oblique arch a segment only of a large
circle, as in the dotted line at 94, so as to keep it the same level
as the other without being so flat at the top, the crown of the arch
is safer, but this can only be done at the cost of getting a queer
twist in the line of the oblique arch, as shown at D, Fig. 93. The
like result of a twist of the line of the oblique arch would occur if
the two sides of the space we are vaulting over were of different
lengths, i.e. if the vaulting space were otherwise than a square, as
long as we are using circular arches. If we attempt to make the
oblique arches complete circles, as at Fig. 96, we see that they must
necessarily rise higher than the cross and side arches, so that the
roof would be in a succession of domical forms, as at Fig. 97. There
is the further expedient of "stilting" the cross arches, that is,
making the real arch spring from a point above the impost and building
the lower portion of it vertical, as shown in Fig. 98. This device of
stilting the smaller arches to raise their crowns to the level of
those of the larger arches was in constant use in Byzantine and early
Romanesque architecture, in the kind of manner shown in the sketch,
Fig. 99; and a very clumsy and makeshift method of dealing with the
problem it is; but something of the kind was inevitable as long as
nothing but the round arch was available for covering contiguous
spaces of different widths. The whole of these difficulties were
approximately got over in theory, and almost entirely in practice, by
the adoption of the pointed arch. By its means, as will be seen in
Fig. 100, arches over spaces of different widths could be carried to
the same height, yet with little difference in their curves at the
springing, and without the necessity of employing a dangerously flat
elliptical form in the oblique arch. A sketch of the Gothic vault in
this form, and as the intersection of the surfaces of pointed vaults,
is shown in Fig. 101.
But now another and most important change was to come over the vault.
The mediæval architects were not satisfied with the mere edge left by
the Romans in their vaults, and even before the full Gothic period the
Roman builders had emphasized their oblique arches in many cases by
ponderous courses of moulded or unmoulded stone in the form of
vaulting ribs. These, in the case of Norman building, were probably
not merely put for the purpose of architectural expression, but also
because they afforded an opportunity of concealing behind the lines of
a regularly curved groin rib the irregular curves which were really
formed by the junction of the vaulting surfaces. But when the vault
become more manageable in its curves after the adoption of the pointed
arch, the groin rib became adopted in the early pointed vaulting as a
means of giving expression and carrying up the lines of the
architectural design. On its edge were stones moulded with the deep
undercut hollows of early English moulding, defining the curves of the
oblique as well as of the cross arches with strongly marked lines,
and, moreover, falling on a level with each other in architectural
importance; the oblique vault of the arch is no longer a secondary
line in the vaulting design; on the contrary, the cross arches are
usually omitted, as shown in Figs. 102 and 103 (view and plan of an
early Gothic quadripartite vault); so that the cross rib, which, in
the early Romanesque wagon vault (Fig. 90), was the one marked line on
the vaulting surface, has now been obliterated, and the line of the
oblique arch (E F, Figs. 102, 103) has taken its place.
The effect of the strongly marked lines of the groin ribs, radiating
from the cap of the shaft which was their architectural support, seems
to have been so far attractive to the mediæval builders that they soon
endeavored to improve upon it and carry it further by multiplying the
groin ribs. One of the stages of this progress is shown in Figs. 104,
105. Here it will be seen that the cross rib is again shown, and that
intermediate ribs have been introduced between it and the oblique rib.
The richness of effect of the vault is much heightened thereby; but a
very important modification in the mode of constructing it has been
introduced. As the groin ribs become multiplied, it came to be seen
that it was easier to construct them first, and fill in the spaces
afterward; accordingly the groin, instead of being, as it was in the
early days of vaulting, merely the line formed by the meeting of two
arch surfaces, became a kind of stone scaffolding or frame work,
between which the vaulting surfaces were filled in with lighter
material. This arrangement of course made an immense difference in the
whole principle of constructing the vault, and rendered it much more
ductile in the hands of the builder, more capable of taking any form
which he wished to impose on it, than when the vault was regarded and
built as an intersection of surfaces. There was still one difficulty,
however, one slight failure both practical and theoretical in the
vault architecture, which for a long time much exercised the minds of
the builders. The ribs of the vaulting being all of unequal length,
they had to assume different curves almost immediately on rising from
the impost; and as the mouldings of the ribs have to be run into each
other ("mitered" is the technical term) on the impost, there not being
room to receive them all separately, it was almost impossible to get
them to make their divergence from each other in a completely
symmetrical manner; the shorter ribs with the quicker curves parted
from each other at a lower point than the larger ones, and the
"miters" occurred at unequal heights. The effort to get over this
unsatisfactory and irregular junction of the ribs at the springing was
made first by setting back the feet of the shorter ribs on the impost
capping, somewhat in the rear of the feet of the larger ribs, so as to
throw their parting point higher up; but this also was only a
makeshift, which it was hoped the eye would pass over; and in fact it
is rarely noticeable except to those who know about it and look for
it. Still the defect was there, and was not got over until the idea
occurred of making all the ribs of the same curvature and the same
length, and intercepting them all by a circle at the apex of the
vault, as shown in Figs. 106, 107; the space between the circles at
the apex of the vault being practically a nearly flat surface or
_plafond_ held in its place by the arches surrounding it; though, for
effect, it is often treated otherwise in external appearance, being
decorated by pendants giving a reversed curve at this point, but which
of course are only ornamental features hung from the roof. If we look
again at Fig. 104, we shall see that this was a very natural
transition after all, for the arrangement of the ribs and vaulting
surfaces in that example is manifestly suggestive of a form radiating
round the central point of springing, though it only suggests that,
and does not completely realize it. But here came a further and very
curious change in the method of building the vault, for as the ribs
were made more numerous, for richness of effect, in this form of
vaulting, it was discovered that it was much easier to build the whole
as a solid face of masonry, working the ribs on the face of it. Thus
the ribs, which in the intermediate period were the constructive
framework of the vault, in the final form of fan vaulting came back to
their original use as merely a form of architectural expression, meant
to carry on the architectural lines of the design; and they perform,
on a larger scale and with a different expression, much the same kind
of function which the fluting lines performed in the Greek column. The
fan vault is therefore a kind of inverted dome, built up in courses on
much the same principle as a dome, but a convex curve internally,
instead of a concave one, the whole forming a series of inverted
conoid forms abutting against the wall at the foot and against each
other at their upper margins. This form of roof is wonderfully rich in
effect, and has the appearance of being a piece of purely artistic
work done for the pleasure of seeing it; yet, as we have seen, it is
in reality, like almost everything good in architecture, the logical
outcome of a contention with structural problems.
We have already noticed the suggestion, in early Gothic or Romanesque,
of the dividing up of a pier into a multiple pier, of which each part
supports a special member of the superstructure, as indicated in Fig.
90. The Gothic pier, in its development in this respect, affords a
striking example of that influence of the superstructure on the plan
which has before been referred to. The peculiar manner of building the
arch in Gothic work led almost inevitably to this breaking up of the
pier into various members. The Roman arch was on its lower surface a
simple flat section, the decorative treatment in the way of mouldings
being round the circumference, and not on the under side or _soffit_
of the arch, and in early Romanesque work this method was still
followed. The mediæval builders, partly in the first instance because
they built with smaller stones, adopted at an early period the plan of
building an arch in two or more courses or rings, one below and
recessed within the other. As the process of moulding the arch stones
became more elaborated, and a larger number of subarches one within
another were introduced, this characteristic form of subarches became
almost lost to the eye in the multiplicity of the mouldings used. But
up to nearly the latest period of Gothic architecture this form may
still be traced, if looked for, as the basis of the arrangement of the
mouldings, which are all formed by cutting out of so many square
sections, recessed one within the other. This will be more fully
described in the next lecture. We are now speaking more especially of
the pier as affected by this method of building the arches in recessed
orders. If we consider the effect of bringing down on the top of a
square capital an arch composed of two rings of squared stones, the
lower one only half the width (say) of the upper one, it will be
apparent that on the square capital the arch stones would leave a
portion of the capital at each angle bare, and supporting nothing.[4]
This looks awkward and illogical, and accordingly the pier is modified
so as to suit the shape of the arch. Figs. 111, 112, 113, and 114,
with the plans, B C D, accompanying them, illustrate this development
of the pier. Fig. 111 is a simple cylindrical pier with a coarsely
formed capital, a kind of reminiscence of the Doric capital, with a
plain Romanesque arch starting from it. Fig. 112, shown in plan at B,
is the kind of form (varied in different examples) which the pier
assumed in Norman and early French work, when the arch had been
divided into two recessed orders. The double lines of the arch are
seen springing from the cap each way, in the elevation of the pier. If
we look at the plan of the pier, we see that, in place of the single
cylinder, it is now a square with four smaller half cylinders, one on
each face. Of these, those on the right and left of the plan support
the subarches of the arcade; the one on the lower side, which we will
suppose to be looking toward the nave, supports the shaft which
carries the nave vaulting, and which stands on the main capital with a
small base of its own, as seen in Fig. 112--a common feature in early
work; and the half column on the upper side of the plan supports the
vaulting rib of the aisle. In Fig. 113 and plan C, which represents a
pier of nearly a century later, we see that the pier is broken up by
perfectly detached shafts, each with its own capital, and each
carrying a group of arch mouldings, which latter have become more
elaborated. Fig. 114 and plan D show a late Gothic fourteenth century
pier, in which the separate shafts have been abandoned, or rather
absorbed into the body of the pier, and the pier is formed of a number
of moulded projections, with hollows giving deep shadows between them,
and the capitals of the various members run into one another, forming
a complete cap round the pier. This pier shows a remarkable contrast
in every way to B, yet it is a direct development from the latter. In
this late form of pier, it will be observed that the projection, E,
which carries the vaulting ribs of the nave, instead of springing from
the capital, as in the early example, Fig. 111, springs from the
floor, and runs right up past the capital; thus the plan of the
vaulting is brought, as it were, down on to the floor, and the
connection between the roofing of its building and its plan is as
complete as can well be. In Fig. 113 the vaulting shaft is supposed to
stop short of the capital and to spring from a corbel in the wall,
situated above the limit of the drawing. This was a common arrangement
in the "Early English" and "Early Decorated" periods of Gothic, but it
is not so logical and complete, or so satisfactory either to the eye
or to the judgment, as starting the vaulting shaft from the floor
line. The connection between the roofing and the plan may be further
seen by looking at the portion of a mediæval plan given under Fig.
110, where the dotted lines represent the course of the groin ribs of
the roof above. It will be seen how completely these depend upon the
plan, so that it is necessary to determine how the roof in a vaulted
building is to be arranged before setting out the ground plan.
[Footnote 4: This was illustrated by diagrams on the wall at the
delivery of the lecture.]
Thus we see that the Gothic cathedral, entirely different in its form
from that of the Greek temple, illustrates, perhaps, even more
completely than the Greek style, the same principle of correct and
truthful expression of the construction of the building, and that all
the main features which give to the style its most striking and
picturesque effects are not arbitrarily adopted forms, but are the
result of a continuous architectural development based on the
development of the construction. The decorative details of the Gothic
style, though differing exceedingly from those of the Greek, are, like
the latter, conventional adaptations of suggestions from nature; and
in this respect again, as well as in the character of the mouldings,
we find both sides illustrating the same general principle in the
design of ornament, in its relation to position, climate, and
material; but this part of the subject will be more fully treated of
in the next lecture.
We have now arrived at a style of architectural construction and
expression which seems so different from that of Greek architecture,
which we considered in the last lecture, that it is difficult to
realize at first that the one is, in regard to some of its most
important features, a lineal descendant of the other. Yet this is
unquestionably the case. The long thin shaft of Gothic architecture is
descended, through a long series of modifications, from the single
cylindrical column of the Greek; and the carved mediæval capital,
again, is to be traced back to the Greek Corinthian capital, through
examples in early French architecture, of which a tolerably complete
series of modifications could be collected, showing the gradual change
from the first deviations of the early Gothic capital from its
classical model, while it still retained the square abacus and the
scroll under the angle and the symmetrical disposition of the leaves,
down to the free and unconstrained treatment of the later Gothic
capital. Yet with these decided relations in derivation, what a
difference in the two manners of building! The Greek building is
comparatively small in scale, symmetrical and balanced in its main
design, highly finished in its details in accordance with a
preconceived theory. The Gothic building is much more extensive in
scale, is not necessarily symmetrical in its main design, and the
decorative details appear as if worked according to the individual
taste and pleasure of each carver, and not upon any preconceived
theory of form or proportion. In the Greek building all the
predominant lines are horizontal; in the mediæval building they are
vertical. In the Greek building every opening is covered by a lintel;
in the Gothic building every opening is covered by an arch. No two
styles, it might be said, could be more strongly contrasted in their
general characteristics and appearance. Yet this very contrast only
serves to emphasize the more strongly the main point which I have been
wishing to keep prominent in these lectures--that architectural
design, rightly considered, is based on and is the expression of plan
and construction. In Greek columnar architecture the salient feature
of the style is the support of a cross lintel by a vertical pillar;
and the main effort of the architectural designer is concentrated on
developing the expression of the functions of these two essential
portions of the structure. The whole of the openings being bridged by
horizontal lintels, the whole of the main lines of the superstructure
are horizontal, and their horizontal status is as strongly marked as
possible by the terminating lines of the cornice--the whole of the
pressures of the superstructure are simply vertical, and the whole of
the lines of design of the supports are laid out so as to emphasize
the idea of resistance to vertical pressure. The Greek column, too,
has only one simple office to perform, that of supporting a single
mass of the superstructure, exercising a single pressure in the same
direction. In the Gothic building the main pressures are oblique and
not vertical, and the main feature of the exterior substructure, the
buttress, is designed to express resistance to an oblique pressure;
and no real progress was made with the development of the arched style
until the false use of the apparent column or pilaster as a buttress
was got rid of, and the true buttress form evolved. On the interior
piers of the arcade there is a resolution of pressures which
practically results in a vertical pressure, and the pier remains
vertical; but the pressure upon it being the resultant of a complex
collection of pressures, each of these has, in complete Gothic, its
own apparent vertical supporting feature, so that the plan of the
substructure becomes a logical representation of the main features and
pressures of the superstructure. The main tendency of the pointed
arched building is toward vertically, and this vertical tendency is
strongly emphasized and assisted by the breaking up of the really
solid mass of the pier into a number of slender shafts, which, by
their strongly marked parallel lines, lead the eye upward toward the
closing-in lines of the arcade and of the vaulted roof which forms the
culmination of the whole. The Greek column is also assisted in its
vertical expression by the lines of the fluting; but as the object of
these is only to emphasize the one office of the one column, they are
strictly subordinate to the main form, are in fact merely a kind of
decorative treatment of it in accordance with its function. In the
Gothic pier the object is to express complexity of function, and the
pier, instead of being a single fluted column, is broken up into a
variety of connected columnar forms, each expressive of its own
function in the design. It may be observed also that the Gothic
building, like the Greek, falls into certain main divisions arising
out of the practical conditions of its construction, and which form a
kind of "order" analogous to the classic order in a sense, though not
governed by such strict conventional rules. The classic order has its
columnar support, its beam, its frieze for decorative treatment. The
Gothic order has its columnar support, its arch (in place of the
beam), its decoratively treated stage (the triforium), occupying the
space against which the aisle roof abuts, and its clerestory, or
window stage. All these arise as naturally out of the conditions and
historical development of the structure in the Gothic case as in the
Greek one, but the Greek order is an external, the Gothic an internal
one. The two styles are based on constructive conditions totally
different the one from the other; their expression and character are
totally different. But this very difference is the most emphatic
declaration of the same principle, that architectural design is the
logical, but decorative, expression of plan and construction.
* * * * *