dome is kept solid up to the haunch of the inner shell, so that this inner shell is abundantly secured, while the outline of the outer shell, from the point where it clears the solid mass below, has a form that would exert a minimum of thrust, though it would hardly be secure without a binding chain. It is noticeable that the inner face of the drum is not vertical, but inclined inward in the form of a truncated cone, which considerably strengthens it against any tendency to yield to the force of thrust in the dome.
Fig. 135.—Section of Wren's rejected scheme for St. Paul's.
The scheme was clearly based on the model of St. Peter's in Rome, to which frequent reference is made in Parentalia as having been in the mind of the architect as he developed his idea. The dome partakes of the character of Bramante's design on the one hand, and of that of Michael Angelo, as finally constructed, on the other. The likeness to Bramante's scheme (Fig. 23, p. 48) is in the form of the inner shell, and its adjustment to the supporting drum. The likeness as to adjustment is
