118 Account of the Mountains of ancient Latium. [Aug. 



bodies, according to him, have been washed from the mountains 

 of ancient Latium, and have been more or less agglutinated 

 together. 



But as no pumice has hitherto been observed in the mountains of 

 ancient Latium, neither these beds, nor the mountains Aventine 

 and the Capitol, and the monti Verdi, can have drawn their origin 

 from these mountains. The tuff of the Monti Verdi, and of the 

 Aventine and Capitol, must rather he reckoned among the most 

 ancient volcanic products of this country, thrown out in the very 

 places where it is now found, and therefore traces of it are to be 

 seen no where else. But in consequence of the great lapse of 

 time since it was produced, it is too much shattered and covered 

 with other minerals brought hither by water, to enable us to find 

 any traces of a crater. Hence, though I admit, with my friend 

 Breislak, that this tuff was thrown out of a crater not far from 

 Rome, I am not of opinion that any thing certain can be pointed 

 out respecting its exact situation. 



As to the common volcanic earth, which abounds in fragments 

 of lava and in leucites most usually decomposed : and the puzzuo- 

 lana which always lies under the common, although their spreading 

 out into beds that cover the whole plain of Rome, may seem to 

 prove that they have been deposited from water; yet I cannot 

 admit them to be derived from the mountains of old Latium, 

 which indeed are sometimes covered with a little earth, but 

 generally of too fatty a nature to be employed for making 

 a cement, and at the same time containing very few leu- 

 cites. Hence, I do not consider it as absurd to suppose, that the 

 lakes Gabinus and Regillus were formerly craters which threw out 

 lava, afterwards spread by the agency of water over the whole 

 plain of Rome. Probably there were even more craters in this 

 plain which are now entirely obliterated. One of them perhaps 

 threw out the melanites which are found at the bottoms of so many 

 mountains of ancient Latium. But the formation of the common 

 volcanic earth and the puzzuolana seems to have been the most 

 recent of all, not only as it covers all the bottoms of the moun- 

 tains, but as it in some places alternates with beds of travertino. 



The peperino, in that part which lies towards mount Albanus, is 

 covered with the same scoria? as the lava sperone, and no doubt 

 with that lava itself. In other parts it is merely covered with an 

 earthy crust which seems derived from its own decomposition. As 

 it is not capable of resisting the action of the weather, its surface 

 is split into soft crusts which are continually going to decay. 



The peperino is divided into distinct beds, from a few feet to 

 more than a hundred in thickness. These may be seen very well 

 on the west side of the hill on which the town Marino stands. In 

 that place beds of harder and softer peperino appear to alternate. 



These beds appear to ascend from all quarters towards the lakes 

 which I have mentioned above. They are almost parallel to the 

 declivity of the hill ; but in that part where the lake Albanus is, 



