Phijsical Structure (rf'tht Site of' Rome. 6 



hereafter to be described ; for they are covered with volcanic 

 ashes, and these last have a covering of more modern depositions 

 from lakes of fresh water, under which vast tracts of Italy must 

 have lain for ages. 



These tertiary deposits compose the low hills which skirt the 

 northern and eastern sides of the Apennines from Piedmont to 

 Otranto. On the Mediterranean side, they have been found in 

 patches at Nice and Savona, but not in Liguria, nor until you 

 come to the territory of Lucca and Pisa, where they occur, and 

 extend into the country around Arezzo, Volterra and Siena, and 

 beyond the latter place as far as Santa Fiora, after which they 

 are covered by the volcanic products which first appear there. 

 Within the Hmits of the volcanic country they appear in several 

 situations, as in the neighbourhood of Todi, Orvieto, Otricoli, 

 at Monterose, about half-way between Rome and Civita Vec- 

 chia. In some places these tertiary deposits rise up amidst the 

 volcanic materials, as will be afterwards shown in speaking of 

 the hills of Rome, in different parts of the Campania, and in 

 the Island of Ischia. 



The volcanic district of Italy is confined to that part of the 

 peninsula which lies between the promontory of Minerva, now 

 Capo Campanella, on the south side of the Gulf of Naples, of 

 which the Island of Capri is a prolongation, and the mouth of 

 the river Umbro (the Ombrone), which lies a little to the south 

 of the Island of Elba, a distance in a direct line of about 230 

 miles. The greatest breadth of this volcanic district is at Radi- 

 cofani, south-west of Clusium, which is forty miles from the sea- 

 shore ; and it is bounded on the east by a line passing through 

 Surrentum, Stabise, Nuceria, Nola, Capua, Teanum, up the 

 valley of the Liris to Frusino, thence in the hne of the Via 

 Latina, passing between Tusculum and Praeneste, Nomentum, 

 Capena, and a line east of the Lacus Vulsiniensis, crossing the 

 river Paglia and the ridge west of Clusium, of which the moun- 

 tain now called Radicofani forms a part, and which rises to the 

 height of 3060 feet ; and thence westward to the mouth of the 

 Umbro. There are also indications of volcanic action within 

 the proper district of the Apennines near Telesia, between 

 Capua and Beneventum ; and even at a considerable distance 

 from the great volcanic district, for Mount Vultur in Apuha, 



