No. VII. — Islands of Procida and Ischia. 343 



racter goes, the serpentine rocks at Monte Traverso, not far 

 from the famous gaseous exhalation at Pietra Mala in the cen-- 

 tral Apennines, as decidedly volcanic ; and Guettard disco- 

 vered serpentine in what he considered volcanic formations 

 between Rome and Loretto.* Faujas de St Fond f mentions 

 a lava in the volcanic district of Auvergne, which, from his 

 description, must undoubtedly be considered as nearly allied 

 to serpentine, and which he characterizes as " compacte argil- 

 leuse, d'*un verd tendre, savoneuse, et repandant une forte odeur 

 terreuse lorsque on souffle dessus." We may add, that Count 

 Borch, when examining the serpentines of Sicily, was, notwith- 

 standing the backwardness of mineralogy at that period, led: 

 to suspect their igneous origin. J 



But besides, we have several reasons for inferring that ser- 

 pentine might be in situ in Ischia, from the minerals with 

 which we should have found it associated. We find that in, 

 one of its most famed localities in the neighbourhood of Flor- 

 ence, it accompanies a marly clay of the same characters as 

 that we are about to describe near Casamicciola in Ischia. It, 

 is according to Ferber bluish grey or yellowish, which fur- 

 nishes the best materials to the potters of Impruneta for their 

 manufacture, becoming of a reddish colour in the fire. It is ac- 

 companied with sulphate of lime, and from the structure appa- 

 rently approaching sometimes to that of steatite, Ferber conjec- 

 tures that it may have had some part in its formation. § Now, 

 in Ischia, the clay in which I conjecture the serpentine to have 

 been imbedded, has all the characters just mentioned. It is 

 besides, accompanied with steatite, || and the springs which 

 issue from it contain sulphate of lime, ^ so that if we can con- 

 ceive the natural formation of noble serpentine in such a spot, 

 we have a very fit matrix prepared for it. But even if we 

 should not be disposed to admit its presence as an indigenous 

 rock, it may at least have been elevated by volcanic explosion 



• Ferber 's Travels, 282, S;c. 



f Mineralogie des Volcans, p. 394. 



X Mineralogie Sicilienne, 8vo. Turin 1780. p. 140. 



§ Travels, 275. 



il Siano, Notizie d'Ischia, § 49. 



IT Andria, Traiato delle acq^e Minerali, ii« 175. 



