9. _Volcanic Bisulphuret of Copper_.—M. N. Covelli, during his examinations of Mount Vesuvius, has observed some particular actions going on, especially in the fumeroles on the eastern side of the mountain, and within the crater. Speaking of the former, he says, “Here there are fumeroles in which pure chloride of lead [p227] sublimes into white and yellow crystallizations, which fusing in the hotter places form nacres, gum, and stalactites. In many parts the sulphuretted hydrogen, evolved within the fumeroles, reacts on the chloride, and forms sulphuret of lead, dispersed in small scales through the scoria. Other fumeroles produce very thin scales of the black oxide of copper; these are very brilliant, metalloidal, and flexible, and are produced by the action of the vapour of water at a red heat on the chloride of copper, which may be observed on disturbing the fumeroles. Here and there the reaction of aqueous vapour on the perchloride of iron produces metalloidal scales of the peroxide of iron; whilst further on, the same vapour, acting on mixtures of the two chlorides, produces oligiste iron in small crystals, aggregated on the scoria. The muriatic acid resulting from these actions, and the sulphuric acid which is formed by the decomposition of hydrosulphurets and sulphates, attack the iron, lime, copper, alumine, potash, &c., in the lavas and scoria, and hence result a number of other productions which line the passages of the fumeroles”. M. Covelli descended into the crater, until within 300 feet of the edge of the large eastern opening, from which the great current of lava flowed in 1822. Here the fumeroles presented the most beautiful crystallizations of sulphate of lime and sulphur. On examining the scoria they were found incrusted and covered with a substance, having all the shades of colour belonging to blue, green, and black. Sometimes it resembled a spider’s web in appearance, sometimes soot deposited in the cavities of the scoria. Many specimens were collected, and also a portion of water condensed from the vapours which issued forth, and which evidently contained sulphuretted hydrogen and muriatic acid. The temperature of the vapour was as high as 85° C., in some places, and even up to 90°, at half a foot beneath the surface. The water being examined was found to contain only a little sulphuretted hydrogen, and a little muriatic acid. The black substance was soon ascertained to be a pure sulphuret of copper. Being analyzed, 100 parts yielded 32 parts of sulphur, and 66 of copper, a loss of two parts being incurred, which accords very nearly with the composition of the bi-sulphuret of copper. The blue and bluish-green substances were found to be mixtures of this sulphuret with sulphate and hydro-sulphuret of copper.