Note 35 — Chapter IV · PART I. THE AQUEDUCTS.
Reading edition
By the side of a plan of Rome in the first volume of his magnificent work (pl. xxxviii.), Piranesi gives a section of the relative heights of the Aqueducts, as compared with each other. The figures refer to the base of each specus above that of the Appian, and the following is the result, according to his measurements, reduced to English feet:—
Above Specus of Appian. Palmi. Feet.
Anio Novus 173.8 127
Claudian 163.2 119
Julian 145.1 106
Tepulan 138.7 101½
Marcian 128.7 92½
Anio Vetus 75.4½ 55½
Virgo 9.3 7
Appian — —
At a lower level than Specus of the Appian.
Alsietina in the Trastevere 37.6½ 27½
He gives as the total full range, i.e. from the specus of the Alsietina (the lowest), to that of the Anio Novus (the highest), as 211.2½ palmi, or 154½ English feet. The height of the Appian, he shews by his diagram to be about 24 English feet above the Quay of the Tiber. The points at which Piranesi obtained his measurements, and the mode employed, are not recorded. It seems hardly possible that the Appia is 55 ft. under the Anio Vetus in Rome.