GENERAL TOPOGRAPHY AND GEOLOGY. 5 
half, and Sabatini of the eastern. For the present, the question must be left an open 
one, and this is the more advisable here, since, whatever be the facts as to the origin 
of the topographic features and structure, they have little- bearing on the predom- 
inantly petrological questions treated of in the present paper. 
Ciminian District. 
The Ciminian District immediately adjoins the preceding one on the north, and 
is bounded on the south by the Sabatinian District. Its area is approximately 900 
square kilometers. It is composed of two distinct volcanoes, that of Cimino on the 
north and of Vico on the south, the former being the earlier. 
The remains of the Cimino Volcano are made up of several hills, including 
Monti Pallanzana, Vitorchiano, Cigliano, and Soriano, surrounding on the west, 
north, and east the main mass of Monte Cimino proper, whose highest point has an 
altitude of 1,035 meters above sea-level. This complex is pretty clearly the remnant 
of a single volcano, though the original structure is largely hidden by the extensive 
erosion which it has undergone and which has been much aided by the tuff-like 
character of most of its rocks. 
Immediately to the south, or rather south-southwest, of Monte Cimino, whose 
southern flanks are partly covered by its ejectamenta, is the better-preserved Vico Vol- 
cano. Vico is a fairly well-preserved volcanic cone of the normal type of strato- volcano, 
the sides sloping up regularly (much more so than in the Vulsinian District) to the 
circular crest, inside which is the small, shallow Lake Vico. North of this lake is 
the site of the last eruption of the volcano, Monte Venere, a small hill, rising 325 
meters above the lake-level, and composed of lava flows with some tuffs and lapilli. 
The lake surface is 507 meters above sea-level, and the steep inner wall of Vico rises 
from loo meters above this on the south, where it is the lowest, to 456 meters at 
Monte Fogliano on the west. Though the almost perfect circularity of the rim is 
marred by the projection of this last summit, there seems to be no doubt that the 
hollow is a true crater and the volcano a simple one, with few parasitic cones. The 
feature of radial valleys eroded in the loose surrounding tuffs is well marked in the 
topography of this volcano. 
Of the towns which may be mentioned, the city of Viterbo lies in the angle 
between the two volcanoes, west of Soriano and north of Vico. About the Cimino 
Volcano we find the villages of Soriano on the east, Vitorchiano a short distance to 
the north, and Bagnaia on the northwest, while around Vico are San Martino near 
the northwest crater rim, Vetralla on the west, Capranica on the southern edge of 
the area, Ronciglione near the southeast shore of Lake Vico, and Caprarola and 
Canepina to the east and northeast. 
Sabatinian District. 
This lies immediately to the south of the Vico Volcano, with whose tuffs its own 
intermingle. The area covered by volcanic rocks is estimated by Moderni at 1,369 
square kilometers, so that in extent it is intermediate between the Vulsinian and the 
