[14] Durm, _Die Dom Kuppel in Florenz_, etc., Berlin, 1887, Plate [I], gives an admirable illustration of the internal system of this remarkable dome, and shows the masonry of the solid base with its clamps and chains, as described in the document quoted by Guasti (note, p. 18).
[15] This idea finds expression in the latest work that I have seen on the subject: _Die Kuppel des Domes Santa Maria del Fiore zu Florence_. Von Paul Wenz, Berlin, 1901, p. 52; also in Durm, _Die Baukunst der Renaissance in Italien_, p. 406.
[16] For a full account of the deliberations held, as well as for much else of importance relating to the building of this dome, see Professor C. E. Norton’s _Church Building in the Middle Ages_, New York, Harper & Brothers, 1880.
[17] But while Brunelleschi appears to have had great natural constructive aptitude, he had not had a sound training or experience in construction. Such training would have taught him that it would not do, under any circumstances, to spring a vault from the top of a wall, and he ought to have learned this from his study of the ancient Roman monuments.
[18] Nelli, _Discorsi di Architettura_, Florence, 1753, p. 74, reproduces an old drawing which purports to show the form of the scaffolding that Brunelleschi employed. This drawing bears the following inscription: “Questa Dimostrazione è di Filippo Brunelleschi Architetto fatta per e Ponti della Cupola di S. M’ra. del Fiore di Firenze nell’Anno M.CCCCXIX e fu quella che mostrò quando fu lasciato in libertà di dover esser solo nell’operazione di d.a cupola senza il Ghiberti suo compagno non avendola voluta dar fuori prima di non essere libero Architetto di da Opera; come sentiranno nella sua Vita scritta da Diversi.” Brunelleschi, in his account of his intentions before the Board of Works (note, p. 19), would not explain his scheme for the scaffolding. He said merely that the vault was to be raised, without centring, to the height of 30 braccia, and from that level upwards, in the manner that should be advised by those who might then have the work in charge.
[19] In his explanation of his scheme before the Board of Works, as given by Vasari, Brunelleschi begins as follows: “Considerato le difficultà di questa fabbrica, magnifici Signori Operaj, trovo che non si può per nessun modo volgerla tonda perfetta, atteso che sarebbe tanto grande il piano di sopra, dove va la lanterna, che mettendovi peso rovinerebbe presto.” _Op. cit._, vol. 2, p. 347.
[20] It may be thought that this would condemn the use of metal clamps in masonry, such as were inserted in the walls of the Parthenon, or the wooden ties that were, in some cases, used in parts of Gothic buildings. But there is a wide difference between such use of clamps and ties, and the binding chains of the great domes of the Renaissance. In the Greek and Gothic work the masonry forms are favourable to stability independently of the clamps and ties. These were inserted either for security against unusual dangers, as from earthquakes, or for temporary security against rupture while the work was in progress, before the interaction of the parts of the system was fully established; but a dome without abutment violates the constant conditions of stability.
[21] _Discrizione e Studj dell’Insigne Fabbrica di S. Maria del Fiore_, Florence, 1733, p. xxi.
[22] _Memorie degli Architette_, etc., Florence, 1785, vol. 1, p. 190.
[23] Fontana, Nelli, Cecchini, and others.