18 



Epomeo. Some of the lavas of Ischia are remarkably brecciated 

 and zoned, 1 — with varieties of grain, texture, and mineral composi- 

 tion. 



The intermediate district between Somma and Ischia, properly 

 called the Campi Phlegrei, including the islands of Procida and Ni- 

 cida, exhibits the traces of between twenty and thirty crateriform 

 basins, many of very large diameter, but in general much degraded, 

 and sometimes almost obliterated, by the erosive action of the sea 

 and of rains on the loose conglomerates of which they are partly 

 composed, and by the ejections of later, neighbouring eruptions. 

 Ten at least of these cones, with their included craters, are however 

 very nearly entire ; such are the Monte Nuovo, produced in the 

 year 1538; Capo Mazza, a hill entirely composed of silky pumice 

 and its detritus ; the Monte Gauro, which incloses a deep circular 

 crater a mile in diameter ; Astroni, which is nearly equal to the 

 last in size, and precisely similar in figure ; the basins of the lakes 

 Averno and Agnano ; the island of Nicida ; the southern extremity 

 of the island of Procida ; the Capo di Miseno; and the Solfatara of 

 Pozzuoli. 



The author disputes the existence of any large vaulted cavity 

 under the floor of the last-mentioned crater; and attributes the rever- 

 beration produced when it is struck sharply, to the cellular nature of 

 the beds of indurated clay which form this floor, and have been de- 

 posited from the washings of the surrounding slopes, and hardened 

 by the influence of heat and moisture. 



The author accounts for the production of two varieties of Piso- 

 lite, which occur in the tufa and decomposed lava of the Solfatara. 

 This hill is recorded to have been in eruption in A. D. 1180; and 

 the present crater may have been formed at that late epoch. The 

 hill which supports the Camaldoli, 1 643 feet above the sea, is a re- 

 markable mass of indurated tufa ; from beneath which, on the N. E. 

 side, crops out a bed of gray-stone, in which a singular, concretion- 

 ary separation has taken place, of the augitic from the felspathose 

 parts ; the former appearing as lenticular patches in a base consist- 

 ing of the latter. This and other somewhat similar lavas in the 

 same neighbourhood, give rise to important inferences as to the 

 condition of such substances at the period of their emission from the 

 earth. The solid tufa of Capo di Monte and other hills envelops 

 shells of the same species with those which at present inhabit the 

 Bay of Naples. It is likewise in some points traversed by vertical 

 veins of a finer and harder matter, seeming to have exuded from 

 the sides of a fissure formed in the rock, before it was completely 

 desiccated. 



The author attributes the formation of all these volcanic hills to 

 vsuccessive eruptions from below the surface of the sea, though on 

 a shallow shore : and, from the existence of loose tufa over the 

 whole plane of the Campagna, and even to some distance up its prin- 

 cipal valleys, he infers that the sea once washed the foot of the 

 Apennines behind Capua; and that this plain has since suffered an 

 elevation of 200 feet at least, — an elevation in which the whole 

 western coast of Italy and the Apennines probably shared ; as ap- 



