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.[1] 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.[2]
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,[3] 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[4] 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 con-
- ↑ Cf. my Development and Character of Gothic Architecture, p. 70 et seq.
- ↑ The turrets, built upon the supporting piers of the interior, give the outside of the drum the aspect of a massive lantern.
- ↑ Cf. Poleni, Memorie Istoriche delle Gran Cupola del Tempio Vaticano, e de' Danni di eisa, e de' Ristoramenti loro (Padua, 1768), p. 29.
- ↑ Milizia, op. cit., vol. 2, p. 325.
