2& Account qftlu 



stagnate in the Pontine marshes. The whole of this range is 

 composed of secondary limestone, and is properly a branch of 

 the Apennines. The Circeian Promontory is a lofty insulated 

 mass, rising 1729 feet above the sea, also composed of limestone, 

 but of a totally different kind from that of the neighbouring 

 mountains of the Volsci, being, geologically speaking, of a 

 much older formation, and belonging to the transition class. 

 There is a remarkable circumstance connected with this rock, 

 for, in the face of the precipice next the sea, it is perforated, at 

 the height of forty feet above the present level of the water, 

 with holes formed by the Mytilus lithophagus, portions of the 

 shell of the animal being sometimes found in the holes, — a clear 

 proof, among many others on this coast, of a change in the re- 

 lative level of the sea and land, since the formation of our pre- 

 sent continents. That the Circeian Promontory was at one 

 time an island, is evident from the proofs that exist of the sea 

 having at one time covered the whole of the Pontine marshes to 

 the base of the Volscian mountains. Excavations made near 

 the sources of the UfFente, which is nearly ten miles from the 

 shore, gave, at the depth of seventy-two feet, sea-sand mixed with 

 shells, and the remains of marine plants in tolerable preservation. 

 Lower down in the marshes, a section across the Appian Way 

 gave, at the bottom, a clay mixed with sea-shells, above which 

 came a bed, between five and six feet thick, of peat, and over 

 that a bed of clayey soil, mixed with fragments of limestone. 



North of the Montes Lepini, connected by a ridge, at the 

 base of which the small town of Ulubrae is supposed to have 

 stood, rises a group of hills, the site of many places of great re- 

 nown, Tusculum, Aricia, Alba Longa, Velitrae; Mons Algi- 

 dus, Mons Albanus, and the Alban Lake. The highest of 

 these hills, Mons Albanus, now Monte Cavo, rises to the height 

 of 3160 feet. Mons Ariemisius, the point which rises imme- 

 diately above Velitrae, is 3018 feet above the sea, and the town 

 of Velitrae itself is situated at an elevation of 1187 feet. These 

 differ in form and structure from any yet named, being wholly 

 volcanic; not, however, composed of recomposed stones from 

 ashes and cinders, but of hard compact lava, streams of which 

 appear on every side ; the waters of the Lacus Albanus and the 



