ITALY. LETTER XIV. 193 



careous incruftation on the afcent of the calcareous 

 hill of Tivoli, near a bridge in a cavern to the 

 right hand of the road ; which proves 4 that thefe 

 fuperincumbent incruftations are by far pofterior 

 to the volcanic alhes. 



The porous -limeftone produced by the calca- 

 reous waters on the defcents, and on the foot of 

 the Apennines near Tivoli, is called Pietra Tra- 

 vertina. It is commonly ufed at Rome, fivoli, 

 and other places, in the mafonry of churches and 

 private houfes. Though found in many other 

 parts of Italy, its original local name is become in 

 Italy a generical one, and it is called every where 

 Pietra Travertina. The quarries, whence came 

 that name, are three Italian miles diitant from 

 ttvoK) and are in fome large hills immediately 

 under the Apennine-limeflone mountains. The 

 rubbifh of thefe quarries is burnt in large heaps to 

 quick-iime. 



Grotta di Nettuno is a deep ravin in the hill of 

 Twol*, by which the great cafcade of ^e^erone 

 falls into the city. This river depofes likewife cal- 

 careous fediments, and many Travertino hills feem 

 to be produced by its former inundations or bed- 

 dings. 



Le Cafcadette defcending from the fame hill are 



very fine. To the right of the road, which leads 



to the oppofne part, whence thefe cafcades are beft 



O feen, 



