Dr. Donati on the Eruption of Mount Vesuvius. 297 



verted cone, of a somewhat elliptical form, was about one 

 hundred and sixty-six toises ; the surface of the upper part 

 consisting of semivitrified lava, containing much amphigene 

 and pyroxene; and from the south-west to the north, divided 

 here and there, like basalt, by vertical fissures, to the depth of 

 two toises. Other varieties of lava which occur here present 

 occasionally capillary amphibole, of a reddish brown colour, 

 produced by the eruption of 1822. 



Many small volcanic mouths (fummaioli) in the interior of 

 the crater, exhaling aqueous vapour, together with sulphureous 

 and muriatic gas, had generated sublimations of muriate of 

 soda and of copper. These apertures, which, during the 

 eruption of 1822., presented a scene completely volcanic, 

 appeared to be re-animated in November, 1824, by an in- 

 crease of temperature, and emitting dry vapours, produced the 

 corneous muriate of lead (cotunnia) already described in the 

 catalogue of Vesuvian productions. 



Active smoking apertures and broad clefts began to be 

 visible in April, 1826, in the interior of the crater facing the 

 north ; from these arose aqueous vapour united with sul- 

 phureous gas, which attacked the lavas, decomposed them, 

 and generated considerable quantities of sulphate of lime in va- 

 rious forms, acicular, radiated, dendritic, and a bouquet. Lower 

 down, but not far from these apertures, were others which 

 afforded sublimations of a blue colour, semi-crystallized, which, 

 upon examination, proved to be the bisulphuret of copper. 

 The last-mentioned apertures no longer exist, having been 

 precipitated into the bottom of the crater, together with part of 

 the sides, to which they were attached. At the bottom of the 

 crater was a large funnel-shaped opening about three toises in 

 depth ; and in June, 1826, appeared two new and active volcanic 

 mouths to the east and north of it. I descended boldly ; but 

 the excessive heat and acidulous vapours impeded respiration ; 

 I could not approach near to the eastern one. The northern 

 one afforded sublimations of trisulphuret of iron, brown and 

 confusedly crystallized in small rhombs ; and abundance of 

 sulphate and persulphate of iron and manganese, and also 

 muriatic salts. Every step and stroke, however slight, on the 



