Physical Structure of the Site of Rome, 19 



it is found, inasmuch as it has given the name to the stone, is 

 Tivoli, the ancient Tibur ; and hence it is called Lapis Tibur- 

 tinusy modernized into Travertino *. 



A great number of the most splendid edifices of ancient and 

 modern Rome are built of travertino, derived from the quarries 

 of Ponte Leucano, on the right bank of the Anio, a little below 

 Tivoli. 



These fresh-water deposits appear in so many places, that 

 there is every reason to believe that they extend over the whole 

 area on which Rome stands. They are found on the sides of 

 the greater number of the hills along the left side of the great 

 valley of the Tiber, and several miles from the city, as far as 

 Monterotondo, which is near the ancient Nomentum. The 

 quantity of travertino and calcareous tufa found on the hills on 

 the left bank from the Porta del Popolo to the Milvian Bridge 

 is astonishing. They form a series of successive horizontal strata, 

 from the bottom to the summit of these heights, and frequently 

 contain impressions of leaves of trees, and encrusted branches. 

 The extensive beds of travertino on the side of the Aventine 

 Hill next the Tiber, and the fresh-water deposits in the inter- 

 montium of the Capitoline, have been already noticed. They 

 are found at the height of 150 feet above the Tiber on the Es- 

 quiline. 



On the right bank, the tower called Torre di Quinto, nearly 

 opposite the confluence of the Anio with the Tiber, which is 

 three miles from Rome, is built upon a mass of travertino, rest- 

 ing on calcareous sand, which sand rests on volcanic matter. 

 Beyond this tower, at Prima Porta, a considerable height above 

 the river, there is a great mass of travertino, full of fresh water 

 univalves. Beds of travertino are also found in that part of the 

 valley which lies between Rome and the sea, particularly on the 

 Via Ostiensis, near Torre di Valle. 



But there is a circumstance connected with these fresh water 

 deposits which is yet to be noticed, of the greatest interest as 

 connected with the physical history of this region, viz. that they 

 are found to contain bones of elephants and other land animals, 



• For a description of the mode of formation of this stone at Tivoli, see 

 Lydl's Friuciples of Geology, vol. i. p. 208. 1st edition. 



B 2 i^i^iiA-luii;. .ii 



