212 Physical Notices on the Bay of Naples. 



chytic tufa at St Anastasia behind Monte Somma. I have 

 also a specimen in which the crystals are placed in cavities of 

 a leucitic lava of so late a date as 1817 ; but the most magni- 

 ficent specimens are those which occur in broad plates as bril- 

 liant as highly burnished steel, and not liable to tarnish. It 

 occurs lining the walls of cavities in calcareous masses. The 

 magnetic or octohedral iron ore also occurs, and abounds in 

 some lavas. 



Sulphur is an abundant production of the active volcano. 

 The hemiprismatic sulphur or red orpiment, in which arsenic 

 abounds, is found in the crater. My specimen was produced 

 by the eruption of 1822. The common or prismatic sulphur 

 is rarely found crystallized, although very pure. It is either in 

 filamentous crusts investing the rocks of the crater, or in glo- 

 bular concretions, or else in acicular crystallizations. 



At the southern base of Vesuvius, about a mile from shore, 

 there is under water a spring of petroleum, from which, when 

 the sea is perfectly calm, bubbles of the mineral oil, the size 

 of a pea, may be seen rising, which, on reaching the surface 

 of the water, make yellowish brown marks three or four inches 

 in diameter, and soon dissipate, leaving a very disagreeable 

 smell, which is carried by the wind to some distance. * It un- 

 doubtedly owes its origin to the volcano. 



Here I must close this imperfect enumeration of the most 

 conspicuous simple minerals of Vesuvius. I shall only add the 

 names of six new minerals from the appendix of Haidinger, 

 which occur here, and generally here alone, but whose charac- 

 ters have been very imperfectly determined. BreislaJcite, (see 

 p. 209;) Comptonite, (see the Edin. Phil. Journal, iv. 131 ;) 

 Forsterite, Humite, Somervillite, and Sulphate of Potash ; 

 likewise Davyne, (see No. xiv. p. 326.) 



The minerals of Vesuvius doubtless require much elucida- 

 tion ; and should Messrs Monticelli and Covelli succeed in 

 their efforts towards this end, they will perform an important 

 benefit to science. I now close this paper with the hope that 

 those who may read it with attention, will, notwithstanding its 

 many imperfections and omissions, derive both pleasure and 

 profit from the perusal. Of this I am convinced, that they 



* This notice is from Breislak, Cainpanic, i. 241. 



