Bafalt. ' 45 3 Let it not be thought prefumptuous, in thofe who have not feen living volcanos, to conteft the volcanic charadter of foffils witb thofe who have long and often contemplated thofe great pheno- mena; for, the rauft ingenuous of thofe who have beheld the(e eruptions acknowledge that very lit- tle is to be learned from them. Collini, who twice afcended Vefuvius. and witneffed its erup tions, complained that he was thereby no way forwarded in volcanic knowledge. Strange af- firms that the view of extindt volcanos is much more inftrudlive. " The phaenomena of recent “ volcanos (fays he) are very little caldulated to “ give us much inftrudtion. A few days tour in “ iuch countries as Auvergne, Velais, and the « Venetian ftate, are worth a feven years appren- « ticefhip at the foot of Vefuvius or AEtna.” In effcft, lavas, pouzzolana, tufas, &c. may as well be examined at a diltance as in the neigh- bourhood of volcanos, and are generally brought to diftant countriesas objedts of curiofity ; but amygdaloids, and decayed porphyries, and vvackens, which bear a ftrong refemblance to volcanic produdts, are not much attended to, nor commonly known by volcanic obfervers, and hence when they quic real volcanic countries, and mcct thefe, they miftake them for thofe produfts to which their eyes were accuftomed, and from theories poffibly very' lublime, but perfedHy ro- mantic. , r r Sir William Hamilton difcovered a few frag- ments of bafaltic columns, ejefied by Mount Ve- iuvius during the eruption of 1779- Th is Baron Veltheim deems a ftrong proof of his theory ; namely, that bafalts are formed by cryftalhza- tion in the bottorn of volcanos; to me, however, 0 g 3 1C