Notice of Active and Extinct Volcano^. 259 



rests on too slender grounds to deserve a place in a scientific 

 treatise." 



" The soil of Rome, as an eminent Italian geologist has since 

 fully proved, is in reality composed of an alternation of sandy or 

 calcareous beds, with a tuff containing fragmentsfof scoriform as 

 well as compact lava, often rolled, and accompanied likewise 

 with pebbles of the Appenine limestone, that display evident 

 marks of attrition. There is however no proof that these frag- 

 ments of lava were ejected by any volcano which occupied the 

 immediate site of Rome, on the contrary the nearest spot from 

 which we can suppose them to be derived, is the Lake of Albano, 

 more than twelve miles distant." 



" The whole of the country for several miles around Alba- 

 no, abounds in volcanic appearances. Amongst the mountains in 

 this group are no less than four lakes, which appear originally to 

 have been craters, the one already mentioned, that of Nemi, 

 Joturna, and Vail. Aricia. With respect to the latter place, 

 Pliny mentions a report that the ground would set fire to charcoal, 

 and Livy notices a shower of stones that fell there, as well as the 

 bursting out of a warm spring, having its water mixed with 

 blood, which Heyne supposes to have been bitumen. 



" Yet the differences of mineralogical character between the 

 volcanic rocks of these mountains, and those found at Rome it- 

 self, oblige us to abandon the idea that the latter can have been 

 derived from the same quarter. The hills in the immediae vi- 

 cinity of Rome, consist of that aggregate of volcanic materials 

 which all are agreed to designate as tuff, whilst the neighbor- 

 hood of Albano is constituted of a material which the Italian 

 geologists have chosen to mark as a separate rock under the 

 name of Peperino. It is easy, says Von Buch, to distinguish these 

 two substances ; in peperino nearly the whole mass is fresh, unde- 

 composed, and bright to the eye, whereas in tuff the greater part 

 is dull, and appears weathered. The former resembles a porphy- 

 ry, the latter a sandstone and other similar aggregates. The sub- 

 stance, of which peperino consists, preserves almost uniformly 

 an ash-grey colour, but the tuff of Rome is generally darker. 

 With respect to its fracture too, peperino is less friable than tuff, 

 and the mica, which is distributed over it either in detached plates, 

 or collected into masses, sometimes as large as a cannon-ball, 

 mixed with crystals of augite and magnetic ironstone, preserves 

 its original black colour and lustre, which in the tuff is not the 

 case." 



Professor Daubeny is of opinion not only that the materi- 

 als constituting the immediate substratum of Rome and of 



