llo or Circeo, between which and
Tarracina lies the southern part of the Pomptine marshes. The intended
cut must therefore run nearly in the direction of the Via Appia and to
the west of it. But considerable cuttings would be required on that
more elevated part of the Campagna which lies between the mountains of
Alba and the nearest part of the coast. The basin of the Pomptine
marshes is bounded by the offsets of the Alban mountains, the Volscian
mountains, and the sea. In the central part it is only a few feet
above the sea-level, and in some parts it is below it. When a violent
south-west wind raises the sea on the coast between Tarracina and
Circeo, the water would be driven into the basin of the Pomptine
marshes instead of flowing out. There would therefore be no sufficient
fall of water to keep the channel clear, even if the head of the cut,
where it originated in the Tiber, were high enough; and that is
doubtful. The scheme was probably a canal, which with some locks might
be practicable; but if the work could be accomplished, it would
probably have no commercial advantages.]

[Footnote 586: Pometia is the common Roman form, from which comes the
name of the Pometinae, or Pomptinae Paludes, now the Pontine Paludi; the
site of Pometia is uncertain. That Caesar intended to accomplish the
drainage of this tract is mentioned by Dion Cassius and Suetonius.

Setia (Sezza), noted for its wine, is on the Volscian hills (the Monti
Lepini), and on the eastern margin of the marshes. The physical
condition of this tract is described by Prony, in his "Description
Hydrographique et Historique des Marais Pontins," 4to. Paris, 1822;
the work is accompanied by a volume of plans and sections and a map of
the district. A sketch of the physical character of this district, and
of the various attempts to drain it, is also given in the 'Penny
Cyclopaedia,'--art. _Pomptine Marshes_. See also Westphal's two
valuable maps of the Campagna di Roma, and his accompanying Memoir,
Berlin and Stettin, 1829.]

[Footnote 587: Ostia, the old port of Rome, on the east bank of the
Tiber near the mouth of the river. The present Ostia is somewhat
farther inland, and was built in the ninth century by Pope Gregory the
Fourth. There are extensive remains of the old town, but they are in a
very decayed condition. "Numerous shafts of columns, which are
scattered about in all directions, remains of the walls of extensive
buildings, and large heaps of rubbis