THE DOME OF ST. PETER’S
When in the year 1503 Pope Julius II came to the papal chair, the
architect Bramante had recently settled in Rome. Born in Urbino, he
had spent his early manhood in the North of Italy, where he had come
under the influence of the Florentine architect Alberti at Mantua, and
of the early Renaissance masters at Milan and elsewhere. Under these
influences he had acquired a style that was peculiar to the North at
that time. But since coming to Rome he had begun to form a new manner
under the more direct influence of the Roman antique,[36] and he soon
developed a style in which the ancient Roman forms were reproduced with
stricter conformity to the ancient usage, and with smaller admixture of
mediæval features than had before prevailed.
An early work in Rome in which he exhibits this more rigorous classic
tendency is the small building known as the Tempietto in the cloister
of San Pietro in Montorio. It consists of a circular cella with shallow
pilasters, surrounded by a colonnade of the Roman Doric order, and
surmounted by a hemispherical dome on a high drum. It is thus in form
like a Roman temple of Vesta with its dome raised out of the abutting
drum and set upon its top without abutment. A glance at Figures 21
and 22, a part section and part elevation of the temple of Vesta at
Tivoli, and an elevation of the Tempietto, respectively,[37] will show
how great a change Bramante made in the adjustment of the vault to
the supporting drum, while it will show also the essential likeness
in other points between the two monuments. In Figure 21 it will be
seen that the vault is well abutted by the roof of the portico, and by
stepped rings of masonry over the haunch, while in Figure 22 the drum
is raised high above the encircling portico, and the vault is sprung
from its top, and has no abutting rings. The architect appears to have
realized that such a scheme would be unsafe on a large scale, for in
the one which he prepared for the dome of St. Peter’s he took care, as
we shall see, to provide strong abutment.
[Illustration: FIG. 21.--Temple of Vesta, Tivoli, from
Serlio.]
The Tempietto is but a modified copy of an ancient model, and in no
true sense an original design. The changes wrought by the copyist are
not of a creative kind consistent with true principles of building.
The pilasters, and the balustrade with which the order of the portico
is crowned, are superfluous, and the work as a whole shows little
of Bramante’s real ability as an architect. Such merit as it has is
primarily due to the ancient model which he would have done better to
have reproduced more exactly.
[Illustration: FIG. 22.--San Pietro in Montorio, from
Serlio.]
But Bramante manifested his real powers in his project for the
great church of St. Peter, his capital work, which, however, was
never carried to completion. It is well known how Pope Julius II
had conceived the idea of erecting a vast tomb for himself, and
had employed Michael Angelo to prepare the design. We are told by
Vasari[38] that the project submitted by this great artist so pleased
the Pope that he determined to rebuild the church of St. Peter in order
to make it more worthy to enshrine so magnificent a monument. Under
Pope Nicholas V, half a century before, the grand old basilica, that
had stood since the time of Constantine, had been partially demolished,
and a new edifice on a larger scale begun by the Florentine architect,
Rossellino. This work had not progressed very far when it was suspended
on the death of this Pope, and operations had not been resumed until
now, when Pope Julius resolved to demolish Rossellino’s beginning along
with what remained of the old structure, and to make a fresh start with
a still grander scheme, which was prepared by Bramante, who began the
new work in the year 1506.
There is much uncertainty as to the exact nature of Bramante’s design
for the building as a whole. No authentic drawings embodying the
definitive project are known to exist, and in the monument itself
Bramante did not go far enough to show his whole intention. Even what
he actually did cannot be wholly made out with clearness, because
so many other hands were employed after his death. The exact form
of his plan is uncertain, though there appears little question that
it was to be in the form of the Greek cross with towers set in the
external angles, and it is certain that a vast dome was to rise over
the crossing.[39] The work, though considerably advanced, was not
nearly completed when, in the year 1514, the master died. He appears
to have built the great piers for the support of the dome, with their
connecting arches and pendentives, but not to have begun the dome
itself.
[Illustration: FIG. 23.--Bramante’s dome for St.
Peter’s, from Serlio.]
The scheme was to be a colossal one, and the dome was to be its main
feature. We may presume that Bramante naturally shared the universal
feeling of admiration for Brunelleschi’s dome, and that he wished to
rival its imposing character. But his ardent and intelligent study of
the monuments of Roman antiquity had given him a better appreciation
of their superior structural merits, and in his project for the great
dome he had sought to adhere more closely than Brunelleschi had done to
the ancient principles and ancient forms.
In seeking guidance from the antique two monuments in particular
appear to have appealed to him as offering appropriate suggestions,
the Pantheon and the Basilica of Maxentius, then called the Temple
of Peace. The first of these monuments gave the model for a mighty
hemispherical vault securely suspended over a vast area, while the
second offered an example of a stupendous system of piers and arches.
In maturing his great scheme with these models before him, he conceived
the idea of uniting their respective sublimities, and is said to have
boasted that he would set the Pantheon upon the arches of the Temple
of Peace. While it is probable that the majestic elevation of the
dome of Florence haunted his imagination, and led him to feel that
he must lift his dome high, he wished, at the same time, to give
the design a more classic character, and a sounder structural form.
In striving to accomplish this double purpose Bramante produced a
scheme for an elevated dome of almost thoroughly Roman character, and
at the same time of imposing external effect. The architect Serlio
gives an illustration[40] (Fig. 23) of this project which is highly
instructive.[41] A comparison of it with the scheme of the Pantheon
shows a close likeness in essential forms and adjustments. The points
of difference are mainly such as Bramante’s desire to make his dome
externally conspicuous would require. In the Pantheon (Fig. 24) the
dome springs from within the massive drum at a level far below the
external cornice, so that the wall above the springing forms a solid
and powerful abutment, reaching almost to the haunch of the vault.
Above this a stepped mass of masonry, diminishing in thickness as
it rises, is carried well over the haunch, effectively overcoming
any tendency to yield to the force of thrust. A Corinthian order,
surmounted by an attic, is carried around the wall of the interior,[42]
while the wall on the outside is plain.
[Illustration: FIG. 24.--The Pantheon.]
In Bramante’s project every essential feature of this ancient monument
is reproduced, but with modifications which give a different aspect to
the design as a whole, but do not constitute any such radical departure
from the principles embodied in the Pantheon as those wrought by
Brunelleschi in adapting the scheme of the Baptistery to that of the
dome of the cathedral of Florence. In order to secure greater elevation
for external effect, the architect has raised the springing level of
the dome considerably, though he has still kept it below the top of
the drum. The drum itself is of great thickness, and forms a strong
continuous abutment at the springing, and the haunch of the vault is
loaded with steps of masonry as in the Pantheon, though not quite so
heavily. The lower half of the drum is a solid wall resting on the
pendentives, while the upper part, which is less than half as thick
(Fig. 25), is pierced with eight wide openings, and its inner and
outer faces are each adorned with an order of pilasters alternating
with free-standing columns in the intervals. The upper wall stands on
the inner circumference of the massive lower ring, while an encircling
order of Corinthian columns is ranged on its outer circumference, and
gives an effect of lightness and elegance to the exterior, which,
together with the lantern at the crown of the dome, goes far to
disguise the real likeness of the whole to the Pantheon scheme.
[Illustration: FIG. 25.--Plan of Bramante’s dome, from
Serlio.]
In these changes and additions Bramante was governed by a clear
understanding of the exigencies of his project. He was obliged to
raise the internal order from the place on the ground level which
it occupies in the Pantheon, to the upper part of the drum, in order
to provide a solid foundation resting on the pendentives; and this
compelled him to eliminate the attic story of the Pantheon scheme. The
most radical change was that of substituting the open colonnade for the
solid wall on the outside of the drum. It is doubtful, I think, whether
the drum thus lightened would have had enough strength to withstand the
enormous thrusts of such a dome.
Like the dome of the Pantheon, Bramante’s dome was to be hemispherical
and to have an opening at its crown. Over this he was to set the
lantern which in outline recalls that of Brunelleschi, though it is
of lower proportions, in keeping with the less elevated form of his
dome, and has a small hemispherical dome instead of a conical roof. The
shape of the lantern accords well with the composition as a whole, and
contributes much to the aspiring expression which was now demanded,
without wholly contradicting the classical spirit that the architect
was striving to maintain.
The structural merit of this scheme lies in what it has derived from
the forms and adjustments of the Pantheon. Its weakness consists in the
increased elevation, lifting the dome away from its abutment to such
an extent that it may be questioned whether it could have been made
safe without chains. The thrusts of a hemispherical dome are vastly
more powerful than those of a vault of pointed outline, like the dome
of Florence, but if properly abutted, as in the Pantheon,[43] it is
perfectly safe, and makes a better ceiling than a pointed vault. In
reducing the efficiency of his abutment by raising the springing of the
dome so high, the architect ought to have diminished the force of its
thrust in a corresponding degree by giving it a pointed form. This
would have made it more safe, but it would have been inconsistent with
the classic Roman models to which he was striving to conform.
As for Bramante’s intended architectural treatment of the rest of
the building we have, as before remarked, no precise information. It
appears, however, most probable that he meant to cover the arms of the
cross with barrel vaulting on massive square piers and arches, with a
single order of pilasters such as Alberti had used in St. Andrea at
Mantua, and such as Michael Angelo actually employed, though in a way
peculiar to himself, and probably unlike that in which Bramante would
have done it. For Bramante would, I think, have followed Alberti’s
example in raising the order on pedestals--the great scale of St.
Peter’s especially calling for such treatment. Bramante would have
realized that a single order large enough to rest directly on the
pavement and allow the entablature to pass over the crowns of the
arches of the great arcades, would dwarf the apparent scale of the
whole interior, as Michael Angelo’s order actually does. But whatever
his intention was as to these details, Bramante died before they could
be carried out, and we are left in the dark as to what the church as a
whole would have been had he lived to complete it.
To the work of his numerous successors prior to the appointment of
Michael Angelo, we need give no attention because their labours did
not materially affect the final result. Their work was largely on
paper only, and the building as it now exists is substantially Michael
Angelo’s design, based on that of Bramante, but with extensive, and
damaging, additions by subsequent architects.
[Illustration: FIG. 26.--The model.]
Michael Angelo at the time of his appointment as architect, in the year
1546, was seventy-two years of age. He professed great respect for the
original scheme of Bramante, yet he radically changed the form and
adjustment of its main feature, the dome. In conformity with Bramante’s
project, he made the drum massive at the base and thinner above, but in
place of Bramante’s external colonnade surmounted by a solid ring of
masonry, forming a continuous abutment at the springing of the vault,
he substituted a series of sixteen isolated buttresses, and raised the
dome so high above them that they do not meet its thrusts at all. The
drum is carried up above the buttresses so as to form an attic over
the order with which the buttresses are ornamented, and from the top of
this attic the dome is sprung. The stepped circles of abutting masonry
at the haunch are omitted, and instead of one solid vault shell, such
as Bramante intended, Michael Angelo’s project provided for a variation
of Brunelleschi’s double vault, and was to include (as the model,
Fig. 26, shows) three separate shells.[44] The inner shell was to be
hemispherical (Michael Angelo thus showing that he appreciated the
superior character of the dome of the Pantheon and that of Bramante’s
scheme to the dome of Brunelleschi as to internal effect), while the
other two were to be pointed, with diverging surfaces. Following
Brunelleschi, he introduced a system of enormous ribs rising over the
buttresses of the drum, and converging on the opening at the crown of
the vault. These ribs unite the outermost two shells, extending through
the thickness of both, and support the lantern.
Of this hazardous scheme only the drum was completed when Michael
Angelo died. But the existing dome, which was carried out by his
immediate successors, is substantially his design, though the innermost
shell of the model was omitted in execution, and the vault was thus
made double instead of three-fold (Fig. 30). This dome does not,
however, divide into two shells from near the springing, but is carried
up in one solid mass almost to the level of the haunch. Michael Angelo
may have thought that this would strengthen it, but the solid part
has not a form capable of much resistance to thrust, and the isolated
buttresses are located so far below the springing that they contribute
practically nothing to the strength of the system, as already remarked,
and as we shall presently see.
Although this great dome has been almost universally lauded, it is
entirely indefensible from the point of view of sound principles of
construction. The work shows that Michael Angelo was not imbued,
as Bramante had been, with a sense of the essential conditions of
stability in dome building as exemplified in the works of Roman
antiquity. He had conceived an ardent admiration for the dome of
Florence, and in emulation of it he changed the external outline from
the hemispherical to the pointed form, and, lifting it out of the
buttressing drum, set it on the top.[45]
[Illustration:
_A_ FIG. 27. _B_]
This vast dome is an imposing object, but it is nevertheless a monument
of structural error. Not only does its form and construction render it
much less secure than Brunelleschi’s dome, but its supporting drum is
entirely unsuited to its function, save as to its strength to bear
the mere crushing weight of the vault. In replacing the continuous
colonnade, with its abutting load, of Bramante’s drum by the isolated
buttresses, Michael Angelo ignored the true principle of resistance
to the continuous thrusts of a dome. It has been thought that the
rib system justifies this, that the ribs gather the thrusts upon the
buttresses and give the dome a somewhat Gothic character. But this
cannot be so. It is impossible for a dome to have any Gothic character.
In addition to what has been already said (p. 20) on this point, it
may be further remarked that, so long as the surfaces between the ribs
remain straight on plan, as in the dome of Florence, or are segments
of a hemisphere, or of a dome of pointed form on a circular base, like
the dome of St. Peter’s, no ribs can be made to act in a Gothic way.
A circular vault on Gothic principles would necessarily be a celled
vault, more or less like the small vault of the Pazzi already described
(p. 27). In such a vault there would have to be an arch (in a true
Gothic vault a much stilted arch) in the circumference of the drum over
the space between each pair of ribs. The crowns of these arches would
reach to a considerable height, in a developed Gothic vault to nearly
or quite the height of the crown of the vault itself. The triangular
spaces enclosed by these arches and converging ribs would then be
vaulted over by slightly arched courses of masonry running lengthwise
of the triangle, or from the arches to the ribs, and approximately
parallel with the crown of the cell (_A_, Fig. 27). Thus in
place of an unbroken hemispherical or oval vault, we should have one
consisting of deep cells. The drum would have to rise far above the
springing, and the haunches would need to be loaded with a solid
filling of masonry. The vault would thus be completely hidden from view
on the outside. Nothing short of this would produce a circular vault
on Gothic principles, or one in which the ribs could act in a Gothic
way.[46] The nearest approach to such a form, in a vault that may with
any propriety be called a dome, occurs over the crossing of nave and
transept in the old cathedral of Salamanca in Spain (Fig. 28).[47] But
this vault has a very different character from the imaginary one just
described. It rises from the top of a high drum resting on pendentives,
and is built on a system of salient converging ribs. The spaces
between these ribs are vaulted over with courses of masonry slightly
arched from rib to rib, and thus running in a direction perpendicular
to that of the courses in a Gothic vault cell, as in _B_, Figure
27. A series of hollowed gores are thus formed which give a scalloped
instead of a plain circular plan to the vault as a whole. But such a
vault differs fundamentally from a Gothic vault. For the line of the
crown of each cell is the steep segmental curve _ab_ in _A_,
Figure 29. In other words, the vault as a whole is a hemisphere with
its surface broken into shallow hollows like the gores of a melon.
It is obvious that in a vault with cells so shaped the thrusts are
as great at all points in the circumference as they are in a simple
hemispherical dome, and that such a vault can have no Gothic character.
To develop this into any real likeness to a Gothic vault, it would be
necessary to reduce it to an unbroken circular plan by cutting off the
scallops at its base so that it would fit into the circular drum, upon
the inner surface of which it would now intersect in series of small
arches, one for each hollowed gore, with its springing at the point
_d_ and its crown at the point _c_. Then these arches would
have to be raised by stilting and pointing until their crowns were
brought up to the level, or near the level, of the point _b_ as in
_B_ of the same figure. Thus the line _dc_, which represents
the height of the arches in the first stage of this development,
becomes the line _ac_ in the second stage. So long as the chord of
the arc _bc_ is a steeply inclined line, the vaulting cells cannot
bear upon the ribs, nor can the thrusts of the vault be concentrated in
a Gothic way.
[Illustration: FIG. 28.--Interior of dome of Salamanca.]
[Illustration:
_A_ FIG. 29. _B_]
The vault of Salamanca is not a Gothic vault in any sense, though its
rib system and its hollowed cells conform with the earliest stage of
apsidal vault development leading to Gothic.[48] It is a dome, and like
the larger dome of St. Peter’s, it is sprung from the top of the drum;
but unlike St. Peter’s dome, it is powerfully abutted by turrets and
dormers built against its springing and its haunch, and it is loaded at
the crown with a cone of masonry, so that from without it looks like a
stumpy spire, and not like a dome.[49]
But Michael Angelo’s vault has not even such remote approach to
Gothic character as the small dome of Salamanca has. Its surface
is unbroken by any hollowing into cells. It is a perfect circle on
plan, and its ribs, which are embedded and not salient on the inside,
cannot, therefore, sustain the vault in any Gothic way. This dome
has, moreover, so much of a spherical shape as to give it a stronger
tendency to thrust than the dome of Florence has, and the thrusts are
exerted equally on all points in the circumference of the drum. The
isolated buttresses are therefore illogical, and being set against
the drum only, and not even reaching to the top of the drum, they are
ineffectual. Thus though the dome was bound with two iron chains, one
placed near the springing, and the other at about half the vertical
height of the vault,[50] it began to yield apparently soon after its
completion. Fissures opened in various parts of both dome and drum
which at length caused such apprehensions of danger, that Pope Innocent
XI called a council of the most able engineers and architects of the
time[51] to examine into the extent of the damage, and ascertain
whether serious danger existed. This council concluded that the cupola
was in no danger of disintegration, and the Pope, in order to restore
confidence in its safety, charged Carlo Fontana, the architect, to
write a book on the building and prove the groundlessness of any
fears of its collapse. Thus the matter appears for the time to have
been dropped. But subsequently the condition of the structure became
so alarming that three eminent mathematicians, among whom was the
celebrated Boscovich, were, in the year 1742, commissioned by Pope
Benedict XIV to make a further examination and submit a report with
recommendations for its consolidation.
The condition of the fabric at the time of this examination will be
understood from Figure 30, a reproduction of the illustration subjoined
to the mathematicians’ report.[52] They found the structure, as the
illustration shows, rent into numerous fissures, some of which were
large enough to allow a man’s arm to be thrust through them. In some
places these cracks had been filled up with brick and cement, and new
ones had opened in the filling.[53] At what time the ruptures had
commenced could not be definitely ascertained, but the mathematicians
express the opinion, for which they state their reasons, that they
may have started very soon after the completion of the work.[54] That
they were not due to any weakness in the substructure was shown by the
fact that this remained apparently quite firm. Had the fractures been
caused by any weakness in the piers or pendentives, the mathematicians
say,[55] they would be wide at the base of the drum, whereas they were
found (as shown in the illustration) to be small at the base and to
increase in magnitude toward the top of the drum, and in the region of
the haunch of the dome. This was thought by them to show that they were
clearly due to weakness resulting from the form of the structure. The
report states[56] that the weight of the lantern had caused the heads
of the great ribs to sink, the dome to expand at the haunch and at the
springing, and the wall of the drum to be pressed outward at the top.
To consolidate the fabric they recommended that additional chains be
placed at various levels, the old ones having, they thought,[57] burst
asunder by the force of the thrusts; but this could not be verified
because they are embedded in the masonry. They also recommended clamps
of iron to hold in the buttresses.
[Illustration: CVPOLA DI S PIETRO
FIG. 30.--The dome with its ruptures.]
The Marquis Poleni of Padua, a distinguished engineer of the time,
was then called to examine the dome and to take such means as he might
judge most effective to secure it against further disintegration.
Milizia tells us[58] that Poleni, after careful examination, expressed
the opinion that although the cupola had not the catenary outline which
he considered the best for stability, it had nevertheless a good form,
and was in no danger of ruin. He pronounced the fissures of no material
consequence,[59] and attributed them to two classes of causes. The
first of these he thought was haste in construction. The dome having
been built in twenty-two months with materials of unequal quality,
and not carefully laid, unequal consolidation resulted and caused
numerous ruptures. The second class of causes he considered to consist
in the action of heat and cold, humidity and dryness, lightning and
earthquake. Thus far, says Milizia, the reasoning of Poleni is just,
and worthy of his great mind, and he adds, “It would seem, then, that
since the cupola was solid, it ought to have been left in peace, but he
nevertheless advised five chains, which were placed under the direction
of Vanvitelli.”[60] The first of these chains was located at the base
of the drum, the second at the level of the attic, the third at the
springing of the dome, the fourth above the haunch, and the fifth
around the opening at the base of the lantern.
[Illustration:
Plate III
DOME OF ST. PETER’S
Rome]
Poleni, in his own book, is not wholly consistent in what he says of
the dome. While affirming its form to be admirable and its strength
sufficient, and attributing the ruptures to other causes than those
inherent in the nature of the design, he yet, in another place, admits
that they may be to some extent due to the shape of the vault which
he here pronounces not high, or acute, enough.[61] His admiration for
Michael Angelo makes it hard for him, as a rule, to find any radical
defect in the composition; but this passage, and the fact that he
caused the additional binding chains to be applied, would seem to show
that he had misgivings, and did not consider the monument so entirely
safe as the general tenor of his book would lead us to believe. And
the same misgivings are betrayed in what is said by the numerous other
writers whose opinions are cited by him, though like himself they write
for the most part with a manifest bias in favour of Michael Angelo.
Thus one of these writers proposes that the outer covering of lead
should be stripped off on account of its weight, and be replaced with
copper, to which Poleni objects,[62] affirming that the weight is an
advantage, and tends to hold the dome together. Another writer suggests
that the lantern be removed in order to relieve the fabric of its
weight. Another thinks that the buttresses should be heavily weighted
with statues. It was also proposed that additional buttresses should
be set against the attic of the drum, and carried up against the dome
itself; and again it was proposed that massive abutments be built up
over each of the four great piers, but to this it was objected that
the additional weight of such abutments would dangerously overcharge
the substructure. The most radical suggestion was that both dome and
drum be demolished and rebuilt in a more pointed form. All of these
suggestions were rejected, and it was finally decided to employ the
additional chains proposed by Poleni as already stated.
The dome of St. Peter’s (Plate III) was conceived in a grandiose
spirit, which, while it drew inspiration in part from the ancient Roman
source, recklessly disregarded the lessons which Roman art should teach
as to principles of construction. I have said that Brunelleschi led
the way in a wrong direction when he set his great dome on the top
of its drum, and had resort to clamps and chains for the resistance
to its thrusts that should have been given by abutment. In following
his example, Michael Angelo wandered still farther from the path of
true and monumental art. To make a dome on a large scale a conspicuous
object, from the springing to the crown, is a thing that cannot be
safely done in stone masonry. To make it stand at all, resort must be
had to extraneous and hidden means of support, and even these are of
uncertain efficiency for any length of time. The ancient Roman and
the Byzantine builders settled, I think, for all time the proper mode
of constructing domed edifices. Bramante had recognized this, and
while striving to include in his design for the dome of St. Peter’s
as much as he could of the new character embodied in Brunelleschi’s
dome, he tried at the same time to keep safely within the limits of
the principles that had governed the ancient practice. He gave as much
elevation to his dome as he thought these principles would allow, but
even this, as we have seen, was too much, and in greatly increasing
this elevation, so as to leave the dome entirely without abutment,
Michael Angelo took unwarrantable risks, and lent his genius to the
support of false principles.
That this has not been generally recognized is due to the fact, already
remarked, that the architects and leaders of taste of the Renaissance
have made too little account of structural propriety, and structural
expression, as a necessary basis for architectural design.
Recent writers have ignored the condition of this monument. They do
not appear to be aware of it; and although it has been fully set
forth, and discussed at great length by the earlier Italian writers,
few of them have found the true cause in its flagrant violation of the
fundamental laws of stability. They attributed the alarming progress
of disintegration, as we have seen, to accidents and circumstances
of various kinds; and have sought to shift the responsibility to the
shoulders of Bramante. They have affirmed that he did not take enough
care to make his foundations secure. There appears to be some justice
in this, though since his work was strengthened by his immediate
successors[63] the ruptures in the dome cannot, according to the
mathematicians, be attributed to this. The remarks of the old writers
on Bramante must, I think, be taken with some allowance. Their bias
against him is very marked. Thus Poleni quotes Condivi, a disciple
of Michael Angelo, as saying, “Bramante being, as every one knows,
given to every kind of pleasure, and a great spendthrift, not even the
provision given by the Pope, however much it was, sufficed him, and
seeking to expedite his work, he made the walls of bad materials, and
of insufficient size and strength.”[64]
A great deal has been said of the beauty of St. Peter’s dome. It
has been held up as a model of architectural elegance by countless
writers from Vasari down. But no abstract beauty, no impressiveness
as a commanding feature in the general view of the ancient city
that it may have, can make amends for such structural defects. Its
beauty has, however, I think, been exaggerated. Its lack of visible
organic connection with the substructure makes it inferior in effect
to the dome of Florence, where the structural lines of the edifice,
from the ground upward, give a degree of organic unity, and the
buttressed half-domed apses, grouped in happy subordination about the
base of the drum, prepare the eye to appreciate the majesty of the
soaring cupola as it rises over them. The dome of St. Peter’s has
not the beauty of logical composition. Beauty in architecture may, I
think, be almost defined as the artistic coördination of structural
parts. As in any natural organic form, a well-designed building
has a consistent internal anatomy, and its external character is a
consequence and expression of this. The dome of St. Peter’s violates
the true principles of organic composition, and this I believe to be
incompatible with the highest architectural beauty.