[194] In the valley of the Caffarella, a stone _specus_ has been made by the side of the natural bed of this branch; it is open at the top, has lochs in it, and is on a higher level than the natural stream. The object of this was obviously to keep a supply of water from the springs in dry weather. [195] The two arches of the Porta Metronia remain, both built of brick of the time of Aurelian. The outer arch is visible in the city wall; the inner one is concealed by a medieval tower built up against it. In the year 1871, Signor Rosa made a new gate on the east side of the Porta Metronia for his carts to pass through, in which the earth, excavated from the Palatine, is carried out into the meadow beyond, outside of the walls. This is certainly better than continuing to fill up the valley between the Aventine and the Pseudo-Aventine, and thereby concealing more of the Wall of the Kings under S. Balbina and burying more of the Aqua Appia, than has already been done under his orders. [196] Cicero, Epist. ad Q. Fratrem, lib. iii. ep. 7. [197] “Hic etiam derivavit aquam de antiquis Formis, et ad Portam Lateranensem conduxit, ibique lacum pro adaquandis equis fieri fecit. Plurima quoque molendina in eadem aqua construxit, et multas vineas cum fructiferis arboribus secus ipsum lacum plantari studiosissimè fecit.” (Muratori, Rerum Italic. Script., tom. iii. p. 420, col. 2, E.) [198] “Aquam ad Urbem reduxit, molendina cum vineis juxta lacum aptavit,” &c. (Pandolphus Pisanus, ibid., p. 419, col. 1, E.) [199] SIXT. V. PONT. MAX. PICENVS. AQVAM . EX . AGRO . COLVMNAE. VIA . PRAENEST . SINISTRORSVM. MVLTARVM . COLLECTIONE . VENARVM. DVCTV . SINVOSO . A. RECEPTACVLO . MIL. XX. A. CAPITE XXII. ADDVXIT. FELICEMQVE . DE . NOMINE. ANTE PONT. DIXIT. COEPIT . ANNO. PRIMO. ABSOLVIT III. M.D. L. XXXVII. [200] See Aqueduct XI. [201] The Pope insisted on the work being completed at the time originally fixed, notwithstanding that the blunder of his engineer made it necessary to rebuild the whole arcade for seven miles. [202] “Nunc autem in urbem influunt: 1. Aqua Appia, 2. Anio Vetus, 3. Marcia, 4. Tepula, 5. Julia, 6. Virgo, 7. Alsietina (quæ eadem vocatur Augusta), 8. Claudia, 9. Anio Novus.” (Frontinus, 4.) [203] Id., c. 19. [204] See Aqueduct III. [205] Frontinus, c. 15, in both cases called by him, Herculaneus. [206] Frontinus, c. 12. [207] Id., c. 5. [208] “Quid loquar aërio pendentes fornice rivos, Qua vix imbriferas tolleret Iris aquas? Hos potius dicas crevisse in sidera montes, Tale giganteum Græcia laudat opus. Intercepta tuis conduntur flumina muris; Consumunt totos celsa lavacra lacus.” (Cl. Rutilii Itiner., l. 1, v. 97. and following.)