narrower aisles, the multiplied obstructive masses of the various piers, hide the dome away from view. Rightly designed, a great central dome ought to be all in all; everything should lead up to it; everything should be suppressed that does not lend it strength or grace. Its thrusts are great, and cannot be resisted by the piers of aisles, unless the piers are positive mountains of masonry; aisles, then, should be omitted. The dome should rest on four arches, and their thrusts should be resisted by the solid walls of the unaisled nave and choir and the two transepts. And these four great limbs of the church should be kept short, to give the dome full value. [Illustration: NAVE.] Again, just as the central dome dictates the plan of the church, so it should dictate the form of the vaulted roof. There were three types of vault at Wren’s disposal. One was the intersecting vault, a second the domical vault, a third the waggon or tunnel vault. The first is altogether out of harmony with a central dome, though Wren has employed it in some of his City churches. What he adopted was the second: he vaulted the nave with a row of four domes, the choir with a row of three. Thus, it might be thought, with seven domes leading up to a central dome, Wren had secured harmony and success. It is not so. Nothing can be more distressing to the eye than to follow the up and down line of the little domes till it suddenly plunges into the central abyss. The only tolerable form of vault in connection with a central dome is the tunnel vault, as it is employed in St. Peter’s, Rome; or, still better, in S. Annunziata, Genoa. Such a tunnel vault, however, should start direct from the cornice, and not, as at St. Paul’s, from a meaningless attic interposed between cornice and vault. [Illustration: CHOIR.]