1850.] MURCHISON — EARLIER VOLCANIC ROCKS OF ITALY. 297 



marly subsoil of the central depression is seen to be a lacustrine de- 

 posit, fig. 3, 5, & fig. 4, 5, which is charged with Lymnece andPlanorbes, 

 whether of extinct or living species I could not ascertain. It is, 

 therefore, clear, that if ever Hannibal's Camp were the crater of a 

 true terrestrial volcano, as I believe it may have been, its activity 

 ceased at a very early period, and the depression became in sub- 

 sequent ages the station of a lake which in its turn was let off, and 

 the ground desiccated, probably ages before the Carthaginian invasion ! 

 A remarkable feature in this depression is, that precisely in its centre 

 is a conical hill called ' Monte di Vescovo,' formed of the same vol- 

 canic materials as the surrounding margin, the escarpment of which 

 is nearly equidistant from the central mount at all points (see Map, 

 fig. 3, page 284, and section, fig. 4). 



Besides the chief central crater or Camp of Hannibal, there are two 

 other parasitic and smaller adjacent craters, one of which is called 

 La Tartaruga, which lie immediately to the south of it, in the valley 

 of La Molara, which separates the group of Hannibal's Camp from 

 the sloping ridges of Tusculum on the north. Whether viewed in 

 nature or on the Map (fig. 3), these smaller craters certainly much 

 resemble some of those in Auvergne, and, like their larger neighbour, 

 they have each broken-down rims on their north-western faces. It 

 is also probable from the nature of the rocks, that the same volcanic 

 matter, which issued in Hannibal's Camp and its parasites, also forced 

 a vent in the Lake of Regillus, and at Colonna on the north, and at 

 Civita Lavinia on the south of this system. 



Having already expressed my opinion that the flanking masses of 

 Alban peperino are of higher antiquity than the scoriaceous rocks of 

 Hannibal's Camp and Monte Cavi, I may say another word or two, 

 better to explain why I thus differ in opinion from my friends 

 Spada and Ponzi. These authors suppose, that the peperino was 

 formed upon land by a sort of lateral mud eruption which issued 

 from the side of the great subaerial volcanic vent. They base 

 their inference chiefly on the fact, that some grass-like vegetables 

 have been found within the peperino which have their stalks pressed 

 down conformably with the slope of what they consider to be the 

 former coulee of mud in which these vegetables descended; and lience 

 they suppose that the peperino flowed upon land. Seeing that these 

 vegetables have not been torrified or carbonized, these authors ex- 

 plain this circumstance, by saying that the mud issuing from the 

 volcano, though hot, was not in a state of fusion. Again, they 

 spoke to me of bones of deer having been found under the ruins of a 

 house at L'Arricia as a proof of terrestrial conditions. But the latter 

 observation had not been verified by their personal inspection when 

 I left Rome, and even if it be in all respects correctly stated, it does 

 not, as it seems to me, establish their case. Masses of matted sedge- 

 like vegetables which grew upon the adjacent Apennines only three 

 or four miles distant, and the bones of deer which fed upon these 

 grasses, may both have been very naturally washed into the waters 

 bathing this coast, at the period when those igneous operations were in 

 activity which I presume gave rise to the solid and massive peperino 



