ROMAN.
87 .
Danube , of a considerable height, and strengthened it by towers at regular distances: itpassed from Newstadt and Uatisbon, over hills, valleys, and rivers, as far as Weimpfenon the Neckar, and terminated at the Rhine , after a winding course of 200 miles. Thiswall was overthrown by the Alemanni , and its scattered ruins may be seen in severalplaces.
A portion of the wall which remains between the Porta S. Giovanni and the Amphi-theatre Castrenses is constructed in the manner called opera laterizia , and is defended withsquare towers, having a base of squared stone of an earlier construction. On theinside the gallery is carried on a series of arches, and is arrived at by staircases in thetowers; the total thickness of the wall is about H feet, and the width of the gallery about4 feet. The towers are in width about 24 feet, and project 12 feet. (Jig. 101.)
Rome was comprised within the circuit of the walls built by Servius Tullius , who alsomore strongly fortified the Capitol , by surrounding the edge of the rock with a stone wall,strengthened by square towers, placed at regular distances. Part of this may be seenon the western side of the Capitoline hill , but the greater portion was destroyed in the timeof the Caffarelli, when its thickness was found to be upwards of 20 feet, built of very largesquared blocks of pepperino.
Near the ruins of the baths of Diocletian, and between the Viminal and Esquiline hills, are the remains of the celebrated Agger of Servius Tullius : it continues for up-wards of 100 feet in length, and to a height of 30 feet. In the middle was placed theViminal gate : the Agger was formed with the earth taken out of the trench in front ofthe wall.
Tiie wall here was formed of squared stone laid in regular courses, and strengthened bysquare towers, ( Dionysio, lib. ix. Strabo , lib. v.): it has been restored and repaired atvarious times : the city at present is entered by sixteen gates. Pliny tells us that thewall of ltomulus had only three, and that of Servius Tullius seven. In the part whichAurelian added on the other side of the river were also three. In the time of Pliny , inthe reign of Vespasian , there were twenty-four gates; and when P. Victor wrote duringthe reign of Valentinian , thirty-seven. In the year 1749, the whole circuit of the walls was
Fig 102.
repaired, and, although built at various times, are to the antiquary highly interesting. Inthe present gate leading to St. Paul, out of the walls, the various changes that have beenmade may be traced: on the left is the Pyramid of Caius Cestius. (See Jig. 102.) Aportion between the Porta del Popolo and Pinciana is built on arches, with deep recesses,and sometimes with two rows of arches, one above the other. The masonry is composed ofopus reticulatum, which was much used in the time of Vitruvius , who considered it notvery durable.
The Muro Torto remains, although much out of the perpendicular: Procopius , whowrote in the sixth century, informs us that near the Pincian gate he saw this rent wall,which seemed to have been long in that state; and that when Belisarius wished to pullit down, he was prevented by the Romans from doing so. Near the Poita Maggiore is
g 4