“Besides these twenty-four cupolas, there is a half cupola at the east, and the great cupola of 108 feet in diameter at the middle of the crossing of the great isles. In this the architect imitated the Pantheon at Rome, excepting that the upper order is there only umbratile, and distinguished by different coloured marbles; in St. Paul’s it is extant out of the wall. The Pantheon is no higher within than its diameter; St. Peter’s is two diameters; this shews too high, the other too low; St. Paul’s is a mean proportion between both, which shews its concave every way, and is very lightsome by the windows of the upper order, which strike down the light thro’ the great colonade that encircles the dome without, and serves for the abutment of the dome, which is brick of two bricks thick; but as it rises every way five feet high, has a course of excellent brick of eighteen inches long banding thro’ the whole thickness; and moreover, to make it still more secure, it is surrounded with a vast chain of iron strongly linked together at every ten feet. This chain is let into a channel cut into the bandage of Portland stone, and defended from the weather by filling the groove with lead. “The concave was turned upon a center; which was judged necessary to keep the work even and true, though a cupola might be built without a center; but it is observable that the center was laid without any standards from below to support; and as it was both centering and scaffolding, it remained for the use of the painter. Every story of this scaffolding being circular, and the ends of all the ledgers meeting as so many rings, and truly wrought, it supported itself. This machine was an original of the kind, and will be an useful project for the like work, to an architect hereafter. “It was necessary to give a greater height than the cupola would gracefully allow within, tho’ it is considerably above the roof of the church; yet the old church having before had a very lofty spire of timber and lead, the world expected that the new work should not, in this respect, fall short of the old; the architect was therefore obliged to comply with the humour of the age, and to raise another structure over the first cupola; and this was a cone of brick, so built as to support a stone lanthorn of an elegant figure, and ending in ornaments of copper gilt.