Note 17 — Chapter IV · PART I. THE AQUEDUCTS.
Reading edition
In the Bullettino dell’ Instituto Archeologico, and the Civiltà Cattolica, for the year 1861, it is stated that for the works of the iron railroad between the Via Labicana and the Via Gabina the specus of the Aqua Appia was found, 450 yards (metres) from the Porta Maggiore. It was constructed of square stone of tufa, and was incrusted with tartar, had an acute vault, which was 5 ft. 9 in. high, and 2½ ft. wide.