ITALY. LETTER XIV. 2OI 



and a flat country of volcanic afhes and hills, to 

 Rome. 



The ground about Rome is generally of that 

 nature , however, there are fome calcareous hills, 

 confifting of white, yellow, or grey porous lime- 

 or marl-flone, with plenty of fea-fhells. Such are 

 the hills which offer on the road of Porta del Po- 

 polo, beyond the vineyard Papa Gmlia, as far as 

 Aqua Acetofa \ fuch are, on the other fide, the hills 

 of the Vatican and monte Mario. I had no oppor- 

 tunity to obferve the extent and run of thefe cal- 

 careous hills on the other fide of Rome ; but the 

 before-mentioned may be eafily furveyed from 7W- 

 nita dl monte and the villa Medici. Some of the 

 feven Roman hills might, upon examination, be 

 found calcareous. 



Before Porta del Pepslo, near Papa Giulia, the 

 hills confift of grey, yellowifh, loofe calcareous 

 earth, mixed with lumps of yellow-brownifli cal- 

 careous oftescolla, produced by incruftated roots 

 and plant-ftems. Near Aqua Acetofa this calca- 

 reous mould is coagulated into a hard lime-done 

 tufo. Monte Mario is grey-yellow calcareous earth,, 

 mixed with fome clay and a fpecies of marl. Here 

 appears above ground a large flratum of loofe 

 great oyiter-fhells, of fmall bivalves, univalves, 

 balani, and echini, covered by red-brown loofe fea 

 apd. This is belt obferved in going by the com- 

 mon 



