[209] “In formis autem Romanis utrumque præcipuum est ut fabrica sit mirabilis et aquarum salubritas singularis. Quod enim illuc flumina quasi constructis montibus perducuntur, naturales credas alveos soliditates saxorum, quando tantus impetus fluminis tot sæculis firmiter potuit sustineri. Cavati montes plerunque subruunt, meatus torrentium dissipantur, et opus illud veterum non destruitur, si industria suffragante servetur.”—(Cassiodori Variar., l. vii. c. 6.) [210] It is possible that the number of nineteen was made up by adding the different branches that supplied the Thermæ of the later Emperors, (Septimius) Severus, Antoninus, Alexander (Severus), (Aurelius) Commodus, Constantinus. To these must now be added the two modern aqueducts, the Marrana and Aqua Crabra [XVII.], united and brought through Rome in the twelfth century in the bed of that branch of the river Almo, and the Aqua Felice [XVIII.], made in the sixteenth; also the Aqua Marcia-Pia, made between 1860 and 1870, which now brings the water of the Aqua Marcia into Rome by a different line. [211] This was also the principal gate of the Sessorian Palace, and was sometimes called the Porta Sessoriana. [212] See Diagrams III. and XIX. [213] See the Plans and Sections of this, Plate XXI. [214] The water pumped out by the steam-engine employed by Signor Rosa was always good clear drinking water, and had all the appearance of coming from an aqueduct; it was sent along an open channel the whole length of the Colosseum, and made a great swamp round the arch of Constantine for several months in the spring of 1875, the outlet for it being made on the outer side of the drain under that arch, which had been constructed by the Municipality about 1866. At last it was observed that an aperture into that drain might easily be made on the inner side, and so avoid the swamp in the road, and washing the foot of the arch. Soon after this the steam-engine was stopped on account of the enormous expense of it, after it had gone on for more than a year, always pumping out good drinking water, and sending it to waste. [215] This article will be found in the _Annales de l’Institut de Correspondance Archéologique_, 1873. [216] Near the Porta Maggiore, and under the arches of Nero. There are two large reservoirs close together in this vineyard, probably the Gemelli of Frontinus. [217] _Descending_ from the reservoir into the old _specus_ under the arches of Nero. [218] The Aqua Marcia was brought again into Rome by a new water company in the year 1870, after several years of very arduous work, and overcoming many difficulties. The company who made this great aqueduct consisted chiefly of English shareholders, with a mixture of French and Italian. It was long under the direction of the late Mr. Shepherd, an Englishman, whose loss was much regretted in Rome, and latterly under a Belgian engineer. [219] See Frontinus de Aqueductibus, c. 5.