ITALY. LETTER XIV. 2Og 



with new ftrata of calcareous tophus, produced by 

 the calcareous waters of the Apennines, or the 

 overflowings of the tophaceous Lago d Tartari 

 and Lago df Bagni. 



Thefe few calcareous hills excepted, the foil 

 about Rome is volcanic, and covered with yellow- 

 brown volcanic allies. Commonly they are loofe, 

 and employed as puzzolana. The greater part is 

 dug alia Porta di S. Paolo near Rome, and by 

 the Tiber fhipped to Civita Vecchia\ whence it 

 is exported into feveral parts of Europe. In monte 

 Verde near Rome, alia Porta Portefe, to the right 

 of the road, thefe ames are ferruminated into a 

 tufo, which is employed at Rome in mafonry and 

 buildings. The varieties of tufo in the different 

 beds of the hill are as follows. 



1. Grey-yellow margaceous tufo, fprinkled with 

 white farinaceous round fpots of calcined or 

 mouldered garnet-like fherls. This tufo is fome- 

 \vhat calcareous as fermenting with acids; but it is 

 likevvife argillaceous, which feems to be owing to 

 an adventitious mixture, or to a fort of difiblution 

 by the air. The white farinaceous fpots are lefs 

 aftedted by acids. 



2. Grey-brown, loofe, friable tufo, with plenty 

 of little white round fpots as the before defcribed ; 

 fomething fermenting with acids, unfit for build- 

 ings. 3. A 



