On other occasions, a skin forms on the surface of the lava, which, gradually thickening, keeps flexible for some time, and then wrinkles or swells or extends and breaks to give egress to the hot fluid within, which, in its turn, skins over and repeats the same phenomena. This I shall call "_Lavas with a united surface_." These, in their course, discharge less smoke than the first, draw out more easily into threads, and, when cold, have a dark colour, something like bitumen or pitch. _The lava with fragmentary scoriæ_, when stretched, breaks easily, discharges smoke copiously, and, when hardened, has a more bluish tint, like clods of upturned earth (_formato di zolle_). It is noisy in its course, because the incoherent scoriæ that it carries along strike and crunch against each other; the other lava flows silently, except for a sort of crackling arising from the actual fracturing up of the solid skin by distension from the liquid matter within. If required to give the mineralogical characteristics of this lava, I would say that it was rich in leucite and contained little or no pyroxene; the fragmentary lava, on the contrary, is poor in leucite and rich in pyroxene. The lavas of 1871 were of the "united surface" character; those of 1872 were "fragmentary," with some characteristics which I shall describe: 1. They were of the clearest tint I have ever seen, when regarded superficially, but, when broken, the fracture was darker than any other lava. 2. They had very little leucite and abounded in pyroxene and olivine, and sometimes contained a few crystals of amphibole. 3. Their specific gravity varied with their porosity; the most compact attained 2·75. 4. These lavas carried along in their course a quantity of scoriæ which had long been subjected to the action of the acids of the fumaroles close to the craters, and also a great many bombs (_bombe_)--that is, round masses similar to those ejected from craters. These varied in size, some having a diameter of four to five meters. They frequently contained a large nucleus of very leucitic lava, like that of 1871, with a larger or smaller quantity of feroligiste (peroxide of iron). Others contained lavas changed by the action of the acid vapours near the craters. These bombs must have flowed out with the lava, for they are found through its whole course, and they were certainly not ejected from the crater; for not only are they found on the lava exclusively, but masses so enormous were not thrown up from the craters during the eruption; those lying on the cone near the craters seldom exceed a decimetre in diameter.