254 Mr Forbes's Physical Notices of the Bay of Naples. 



of submarine volcanos, I shall at present content myself, hoping 

 at a future time ^to recur to the subject in a more general 

 form.* 



Resuming our account of the hill of the Camaldoli Convent, 

 we must notice one fact of importance. Mr Scrope remarks, 

 that a bed of graystone appears beneath the tufa to the 

 N. W. of the hill, though, from the very short abstract I have 

 seen of his paper,-f- the description is not very satisfactory. It 

 would appear, however, to be the same stratum as Breislak par- 

 ticularly notices in this direction under the name of Piperino. % 

 The want of consistent geological nomenclature, especially in 

 what relates to the volcanic forniations, is found to be a great 

 drawback in every inquiry ; but by a combination of the two 

 descriptions, we may arrive at some pretty distinct conclusions 

 on the subject before us. Mr Scrope elsewhere states, § that 

 graystone, according to him> is equivalent to the trachytes of 

 most authors ; and from this gentleman's intimate acquain- 

 tance with the most characteristic trachytes of the extinct vol- 

 canos of Auvergne, we may feel confidence in his designation 

 of this rock wherever he meets with it. We therefore con- 

 sider it as a rough porphyritic rock, composed almost entirely 

 of felspar, and once in a state of fusion. Mr Scrope particu- 

 larly mentions, as occurring in the bed beneath the tufa of 

 the Camaldoli, " a singular concretionary separation of the 

 augitic from the felspathose parts, the former appearing as 

 lenticular patches in a base consisting of the latter."" Breislak 

 describes the base of the rock as whitish, and containing crys- 

 tals of mica and specular iron ; and he draws some curious in- 

 ferences from the form of the cavities interspersed through it, 

 which he says contain basaltic crystals, sometimes resembling 

 pitch-stone, which undoubtedly correspond to the concretion- 

 ary augite of Scrope. The shape of the cavities he describes 



• I have not here touched on the more general and abstract facts, which 

 lead us to the conclusion, that the sea had'formerly a higher level, the marlcs 

 it has left on the rocks of Capri, and this limestone coast of Italy, and the 

 occurrence of shells in the tufas. 



j Phil Mag. New Series, i. 388. 



X Campanie, torn. ii. p. 41, &c. 



§ See Memoir on the Ponza Isles, Geol. Trans. New Series, vol. ii. 



