1st. That, as a rule, openings in walls and between pillars, whether
taking the form of doorways, windows, gateways, or intercolumniations,
should be bridged over by arches instead of by horizontal lintels or
entablatures, though not descending into such purism as to reject the
latter when circumstances clearly point to its adoption.
2nd. That areas enclosed by walls, or by ranges of piers or columns, and
of any reasonable width, should be capable of being covered over,--and,
in buildings of the highest grade, should as a rule be actually covered
over,--by _vaulting_; this rule, however, not being pressed so far as to
exclude level ceilings or timber roofs,--the one the most natural and
economical covering for rooms, and the other for churches, halls,
etc.,--where circumstances forbid the use of vaulting.
3rd. That the decorative system of the architecture should harmonise
with, and result from, these prevailing structural conditions; the
construction and the architectural treatment being, not only in harmony,
but in the most intimate alliance the one with the other.
Now, we all know that Grecian architecture almost ignored the arch,
carrying the horizontal or trabeated system of covering openings to the
highest artistic perfection; doing for that system just everything which
the above-stated conditions would demand for an arched style. _Repose_
was the great sentiment which their architecture expressed; _vertical
pressure_, the one physical condition it had to provide against; whereas
arched architecture (as they say in India) “never sleeps.” It is always
exerting pressure in some other direction than the mere vertical line,
and the physical conditions it has to meet are the resistance of these,
as well as the support of mere weight.
We know, too, that Roman architecture admitted nearly all the
constructive conditions we have demanded, and carried them on to a very
considerable degree of practical perfection. We believe, moreover, that
had not circumstances checked its progress, it would have carried out
these conditions to a much greater extent. As it happened, however, it
did not go so far as to make these structural conditions a leading
artistic element, and the groundwork of a distinctive decorative system;
but, being broken up through political convulsion before such an end was
attained, it bequeathed the task to the descendants of its despoilers,
and long centuries of darkness had to pass by before the work could be
accomplished.
In Roman works, the arched construction was in many cases studiously
overlaid and concealed by the decorative features of trabeated
architecture; and, where an arch was architecturally treated, it was for
the most part by bending round it the mouldings of an architrave or
_beam_: and, where a vault was rendered ornamental, it was often by
repeating on its coved surface the coffered panels which had originated
in a horizontal ceiling; while, in purely arcuated works, such as the
stupendous aqueducts, architectural decoration was usually ignored, and
structural grandeur alone trusted to for beauty. Still, however, enough
was done to convince us that these great builders were on the high road
to a noble solution of the problem, and were only, by external
accidents, stopped short of its attainment.
I am not about to indulge in abstract imaginings as to what an arcuated
style of architecture might be if originated without the aid of previous
associations or traditions; but I would ask you to follow out, with some
reference to the previous Classic styles, and aided by our knowledge of
subsequent developments, the _rationale_ of such a style as that whose
leading conditions I have stated.
We must begin with the simplest elements of the style.
Firstly, then, let us take a mere opening in a wall, whether intended
for a window or for any other use. As in the trabeated system, apart
from architecture, such an opening would be covered by a single block of
stone (Fig. 274), so in an arched system would it be bridged over by an
arch (Fig. 275); and, just in the same manner, if a continuous series of
openings were required, equivalent to a colonnade, the same simple idea
would be repeated,--in the one system horizontal stones lying upon
upright ones (as at Stone House) or upon piers (Fig. 276), and in the
other the openings being covered by a series of arches (Fig. 277); the
_colonnade_ being the ultimate result in the one case, the _arcade_ in
the other.
[Illustration: Fig. 274.]
[Illustration: Fig. 275.]
[Illustration: Fig. 276.]
[Illustration: Fig. 277.]
[Illustration: Fig. 278.]
[Illustration: Fig. 279.]
[Illustration: Fig. 280.]
To architecturalise the arched opening, or the continuous arcade, the
simplest expedients seem to be the insertion between the pier and the
arch of an impost moulding to mark the springing line (Fig. 278); and,
in the arch, either to individualise the arch-stones by chamfering their
edges, as the Romans often did, or to relieve their plain surface by
moulding, the latter being best suited where the stones made use of are
of only moderate size (Fig. 279). The mouldings of the arch may,
however, be continued down the jambs without an impost, and in either
case a projecting rim or hood-mould may be introduced over the main
arch to emphasise the line which separates the arch from the
superincumbent wall (Fig. 280).
[Illustration: Fig. 281.]
[Illustration: Fig. 282.]
These simple changes bring our plain arched opening into something like
an architectural feature; and, if we apply them to a continuous arcade,
the architecturalising process becomes yet more apparent, and it may
readily be carried a step farther by adding pilaster capitals to the
piers (Fig. 281). Another and yet more important step, inasmuch as it is
really the basis of a very marked feature in our arch styles, is the
substitution of columns for the piers of an arcade (Fig. 282); which
columns, having square abaci, are really as well fitted to support the
arch as the square pier itself, and at once give a highly decorative
character to our arcade; and the more so if the jambs are converted into
pilasters.
The abaci, however, of such bearing-shafts ought to be very different
from the delicate finish of the Corinthian capital; for the arch is not
the same inert load which the columns in a trabeated style are destined
to carry. It exerts diagonal as well as mere vertical pressure, and so
demands a firmer base. This led the architects of the early arched
styles, while adopting the Corinthian capital, and perhaps re-using
those of older buildings, to add to it a strong flat stone as an impost
upon which they could safely give the springers of their arches a basis
larger in diameter than the sustaining column. This form,--that is to
say, the Corinthian capital with an added impost,--became traditional,
and we find the imitations of it down to the end of the twelfth century.
We have hitherto supposed our arches to be of moderate depth from
extrados, or outer line, to intrados, or inner line, and our walls,
perhaps, of moderate thickness. Let us, however, assume it to be
necessary to increase the depth of the arch, and that the materials at
hand are not of large size. In some of the Byzantine remains in Central
Syria, where the stone is of great size, we find that they have
architecturalised by mouldings and enrichments only just so much of the
arch-stones as was needful for beauty, and left the rest to go as mere
wall-face; and where such large stones are not made use of, it is common
enough to build the arch in two rims, and only to deal architecturally
with the lower one (Fig. 283) or perhaps to leave both plain (Fig. 284).
[Illustration: Fig. 283.]
[Illustration: Fig. 284.]
Now, the first may be unobjectionable where the wall is of moderate
thickness and the load great, and the second is well suited to large and
massive engineering works; but for ordinary architecture, it is apt to
give too bulky and cumbrous an effect. This naturally suggests the
idea--while allowing the upper range of arch-stones to occupy the full
thickness of the wall--of reducing the lower range to a smaller width,
thus breaking the arch section into resalient angles, and thereby both
lightening its effect and rendering the piers or jambs which support it
lighter and less obstructive to the view (Fig. 285).
[Illustration: Fig. 285.]
Simple as this step may appear, it is one whose importance can scarcely
be over-stated; for it is the starting-point of the entire system of
Romanesque and Gothic arch-moulding; it is the origin of the clustered
columns, and the deeply-recessed and richly-decorated doorways which
mark those styles; and to it we owe in great measure even the traceried
windows which are such leading characteristics of Gothic architecture.
For, as regards arches, we had before but one angle to mould, whereas we
may now have as many as the thickness of our walls will permit, thus
generating at once the great Mediæval system of receding orders, whether
of arches or their jambs; and you will presently see that this gives us
also our clustered columns, which are, in fact, the mere decoration of
the receding orders of the piers.
[Illustration: Fig. 286. Capital from the Crypt, Canterbury.]
Let us now deal with such a pier as is shown in our last figure. It is
clear that the plan of that pier is the same as that of the springers of
the coupled arches which it supports, and that this plan is of a
cross-form. It is not, however, necessary that this plan should be
continuous through the pier, if only an impost is provided of a form
suited to receive this double springer (Fig. 286). It is quite possible
(and is very frequent), to substitute a single column for this
cross-formed pier, giving it a capital whose abacus either assumes a
like plan with the springer (Fig. 287), or, if either octagonal or
round, is suited in size to contain it without either undue projection
or much superfluous space.
[Illustration: Fig. 287. Capital from Ely.]
Let us, however, take another step; and instead of substituting a column
for the group of arch-orders, let us substitute either a smaller column
for each of the four orders, thus supporting the arches by a group of
four columns (Fig. 288); or else let these be united into one complex
pillar formed of portions of four columns (Fig. 289); or, thirdly, let
us place a colonnette under each order, grouping them, either in the
solid or as detached shafts, round a central square pier (Figs. 290,
291). In any of these methods we at once obtain the clustered column.
[Illustration: Fig. 288.]
[Illustration: Fig. 289.]
To the jambs we may apply the same process, either substituting a
colonnette for the inner order, and pilasters for the outer ones, or
_vice versa_ (Figs. 292, 293), or substituting colonnettes or pilasters
for all. I do not know how early this system of using colonnettes to do
merely decorative duty was introduced. We have a specimen of it in the
remains of the church built by Benedict Biscop, at Monk Wearmouth, in
the seventh century, where, as I have stated in a previous lecture, two
baluster shafts are placed in either jamb of a doorway to support the
impost.[34] To go to the far East, we find the system in use in the
Mosque of Touloun, at Cairo, built, I believe, in the ninth century. In
one of the doorways of the cathedral at Mayence, built about the end of
the tenth century, columns and pilasters, with Corinthian capitals, and
crowned by a thick impost moulding, are alternately employed to carry
the four receding orders of the arch. The whole has semi-Classic
details. In the western portals of St. Mark’s, at Venice (close upon the
same period), we find a profusion of detached columns similarly used.
They are of marble and other rich materials, and were probably brought
to Venice from ancient buildings in the East.
[Illustration: Fig. 290.
Fig. 291.
Fig. 292.