The first of these works is the small chapel of the Pazzi in the cloister of Santa Croce. It is a simple rectangle on plan (Fig. 10), with a square sanctuary on the short axis, and a porch across the front. The central area is covered with a circular vault which by most writers is called a dome, but it is not a dome; it is a vault of essentially Gothic form, like two early Gothic apse vaults joined together (Fig. 11). It rests on pendentives, and is enclosed by a cylindrical drum, which forms an effective, though not a logical, abutment to its thrusts, and is covered with a low-pitched roof of masonry having a slightly curved outline. Whether this external covering is connected with the vaulting in any way above where it parts from the crowns of the vault cells it is impossible to discover, because there is no way of access to the open space between the two parts. Through a small opening in the outer shell, near its crown, the hand may be thrust into the void, but nothing can be reached. It is a curious form of double vault, and differs fundamentally from the great double dome of the cathedral. The scheme as a whole is structurally inconsistent; for while the inner vault has the concentrated thrusts of Gothic construction, these thrusts are met by the enclosing drum, and not by the isolated abutments that the vault logically calls for. The sanctuary has a small hemispherical dome on pendentives, and the portico is covered with a barrel vault bisected by another small dome on pendentives. [Illustration: FIG. 12.--Interior of the Pazzi chapel.]