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.
1 Op. cit., p. 399.
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 successors1 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." 2
1 The principal work of Bramante's immediate successors on the fabric itself appears to have been to strengthen the great piers, which seem to have been built too hastily, and on insecure foundations. Poleni tells that in order to strengthen these foundations, well-holes were dug under them and filled with solid masonry, and that arches were sprung between these sunken piers, consolidating the whole. Op. cit., p. 19. 2 Ibid., p. 19.
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 coordination 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.