Note 291 — Chapter III · CIRCULAR CHURCHES.
Reading edition
[The Vaults over the outer aisle of St. Stefano Rotondo were built with hollow pots, the remains of which can still be traced in the outer walls of the 2nd aisle.
Prof. Middleton points out also the existence of rings of earthen pots in the vault of the tomb of Sta. Helena (Woodcut No. 227), and also in the vaults of the Circus of Maxentius, on the Via Appia.—Ed.]