The archæology of Rome, Part 8

by John Henry Parker

It then passes again underground parallel to the city wall for a short distance, and near the Minerva Medica it runs into the bank on which that great wall is carried. A portion of this underground arcade was brought to light in some excavations in 1871, but is now covered up again (2320). After passing underground in the bank on which the wall stands for some distance, it emerges near the Porta Tiburtina, now called Porta di S. Lorenzo (see a plan and section of this in No. 1938*). As the ground here is lower it is on an arcade, one arch of which is made into the gate (21, 1870), and a portion of the specus is very distinctly visible on the southern side of the gate, with an opening into it by which persons can go inside of it (shewn in Nos. 69, 572*, and 1487).

After passing the Porta Tiburtina, it went on upon the bank or outer mœnia of Rome to the Prætorian Camp, and there was a large reservoir for it near the Porta Chiusa, remains of which were visible in the excavations of 1868, with the wall of Rome built across it (shewn in 1059). From this reservoir the three aqueducts, Marcia, Tepula, and Julia, were carried along the side of the old road to the inner gate in the great agger of Servius Tullius on the Viminal, where the railway station has now been made, and where the three Roman princes carried on excavations in 1869, in which they found the upper specus; that of the Julia, which was left open for a time, passing between the cippi or boundary-stones, with inscriptions upon them, recording that the three aqueducts passed there between them.

Another division of the Marcia went along the same line as the Arches of Nero to the Cœlian, and along that hill as far as the great reservoir over the arch of Dolabella; then turning to the left or south, it came to an end above or over the Porta Capena[227]. These words may mean—either, in the reservoir on the cliff of the Cœlian Hill just above the gate, rebuilt in the time of Trajan, of which the remains are shewn in 1147*;—or, in the reservoir in the valley close to the west side of that gate (also rebuilt in the time of Trajan, and now a gardener’s house, as before mentioned). In that case it must have passed over the gate, and the specus that is cut in the wall of the western tower belonged to it (710*).

The general plan of the Aqua Marcia near its source is shewn in 1972*, and the line of its course in 1981*, 1982*; the bridge for it in 1983*.

In the early part of its course, above Tivoli, the new aqueduct for this water, called the Aqua Marcia Pia, is carried on a stone specus upon an arcade, after the same fashion as the old one (a portion of this new arcade is shewn in No. 1553).

IV. The Tepula, and V. The Julia, being carried on the same arcade as the Marcia for the seven miles into Rome, have left remains visible in some places, especially at the Gates of Rome, the Porta Maggiore (31), and the Porta Tiburtina (21, 572*); in other places, they have generally been destroyed. Near the Sette Bassi, there is a portion of the specus of the Julia visible just at the surface of the ground, the other two being then subterranean, as the level is rather higher in this part than usual. This portion has been examined by Signor Moraldi, at a junction whence a branch was carried to supply a reservoir at the great villa called Sette Bassi, and there are remains of the loch in the channel to turn off the water, shewing the same arrangement as in a modern canal. (A plan and section of this is given in 696*.) The specus near this point, built of concrete faced with brick, is also shewn in 1006. The specus of the Marcia is always of squared stone, so that one is readily distinguished from the other. There are remains of a castellum aquæ or reservoir for the Tepula, near the Porta Tiburtina, or Porta Viminalis of Frontinus, now called Porta di S. Lorenzo. This is shewn in the Plan of that Gate, Nos. 1111* and 1238*, and a view of it in No. 25. It is a remarkable building of brick of the first century, and has on a level with the specus a series of small corbels projecting from it, evidently intended to carry a hourd, or wooden balcony as a passage for the Aquarii, and perhaps for defence also. It is incorporated in the great Wall of Aurelian. It projects slightly from the line of that wall, and the end of the specus, with its triangular head, is visible in the angle.

V. Julia.

Between this building and the gate, but within the wall, though on the bank on which it stands, are slight remains of another castellum aquæ, supposed to have been for the Julia (Nos. 26, 869, 1873), which has its external face in the direction of the wall, and must have been concealed by it when that was built. This is also of the first century, as is shewn by the brickwork, and it seems to have been a castellum aquæ by the disproportional size of the buttresses used to support the weight of the water, one of the invariable marks of such a structure. The other mark is the peculiar cement with which the wall is lined, called Opus Signinum in Latin, Coccio Pesto in Italian, which is made of broken pottery, and is the hardest cement that is known; it is often impossible to break it, even after it has been exposed to the weather for centuries.

A plan and section of the ground between the two gates, called by Frontinus Esquilina (S. Lorenzo) and Viminalis (Maggiore), shew the difference of level, and the three aqueducts passing underground in the middle between the two gates, and carried on arches at both ends near the gates (see No. 1938*).