In describing the physical condition of Latium, I shall use the name in the sense in which we find it, for example, in Pliny, where it signifies the country between the Tiber, the Liris, and the Anio, though on the side of the Anio the frontier must not be taken too strictly. In our maps the boundary line is marked along the Anio; but this is incorrect, for not only Tibur is situated on its right bank, but also Nomentum, Corniculum, and other places. Latium, in a physical point of view, consists of three distinct parts. The first is of a volcanic nature, and its central point is the Mons Albanus (Monte Cavo), with which are connected the hills of Tusculum. This volcanic part extends from the Campagna di Roma as far as Velitrae, so that the country, as it approaches the Tiber and the sea, terminates in low hills and almost forms a plain. This part is at present called the Latin Hills (Monti Latini); the ancients have no corresponding name for it, though it is quite isolated. The second part is on the east of the first, and consists of a continuation of the Apennines, which runs across the Anio as far as the Liris; in front of it are the hills of the Hernicans, which are likewise essentially a part of the Apennines, for they consist of limestone and have no traces of a volcanic nature; they extend as far as the borders of the Pontine marshes. Between them and the neighbourhood of Tivoli, the country is low, and in some parts a perfect plain, as in the district where Gabii was situated; but although the country is level, it still shows traces of volcanic agency. This is the country of the Hernicans, with lofty Praeneste and the Latin colonies on the border of the Pontine marshes; further on, as far as the hills, the country contained the Aequian and Volscian towns. Those hills are extremely beautiful, and the high country of mount Algidus lies between them and the volcanic plain of Campania; the district of mount Algidus forms the watershed, the waters on the one side flowing towards the Liris, and on the other towards the Anio and the sea through the Pontine marshes. On the north-east of Velitrae there is a table-land with broken ground. The third part, or the country in the north-west, the west, and south, is of quite a different character, consisting of loose, volcanic ground, puzzolano and tufo, which are products of volcanic eruptions. The Tiber in the neighbourhood of Rome was once an arm of the sea, as is clear from the undoubted investigations of Brocchi, and pure marine sand is found there; but in whatever part of the country a mineral occurs, it always consists of an immense quantity of puzzolano, which in some parts has become tufo. Such is the nature of all the country round Rome, but strange to say, one part of the Aventine contains a vein of limestone. Towards the sea the nature of the country is, I believe, the same. On the coast, the land sinks down and becomes a plain of sand as in many barren