Columns of
Sicily.

in this and other instances, the centre alone is in the prismatic forms, which are sometimes found enclosed in amorphous lava, identically the same with the columns, sometimes in tufa, and sometimes even in volcanic glass. But he seems never to have seen or observed the remarkable articulations, not only convex and concave, but strengthened by projecting angles and recipients, which were first noticed and engraved by Da Costa, and afterwards by Pictet, in their representations of the giants' causey. This striking characteristic, which seems unaccountably to have escaped most writers, can scarcely be ascribed to mere desiccation; but seems rather to rival the process by which nature produces regular rock crystals, in the vast caverns of the Alps, of enormous size, and weighing many

tons.

Other basaltic columns occur in Sicily at Vizzini, where the columns are articulated and a foot in diameter, but only a few feet high, curiously arranged on a curved basis; and they gradually become

irregular, and pass into the amorphous lava. At the Motta, already mentioned, they are about two feet in diameter, partly vertical partly inclined. At the bottom of the colonade the peasants made an aperture, where, on introducing the hand, heat was perceived, and the hand smelled of sulphur. Above are great masses of sand, red drosses, and puzzolana; and he infers that the prisms are in the centre of the volcanic mass. It may be said indeed," that heat thus enclosed becomes inextinguishable; and he mentions that, two years ago, the lava of 1669 being perforated at Catania, flames issued; and within these eight years it yielded, after rain, smoke and great heat. This lava is about two hundred feet in depth, and two miles in breadth, and had run about fifteen miles. Other basaltic columns appear near Bronte, on the west of Etna, which gave a title to the glorious Nelson. They are in beautiful hexagonal groups, which disappear in the incumbent chalk or earthy limestone. Some not only project from one centre,

No modern lava prismatic.

but are bent as if to cover a convex surface. On the east of Etna, the rock of the Cyclops, here also engraved, presents on its east side beautiful columns of primeval lava, disposed in the form of an organ, like the Organ Rock near the giants' causey. Near the castle of Aci, the ancient Acis, are found masses of lava in balls, with concentric layers, eight or ten inches in diameter, involved in a bed of bluish volcanic glass. The superincumbent limestone has infiltrated and crystallised in the little cavities of the glass. A reddish baked clay also appears, and little prisms of lava about two inches in length. In the neighbourhood volcanic balls are also found in tufa, with fragments of lava, glass, drosses, and sand. They are generally about six inches in diameter, and often break into regular pyramids, which are joined in the centre as in balls of pyrites; which, he might have added, marks the same influence of iron*. Our learned author totally denies, even

* P. 95, 116, 123, 135, 137.

in opposition to his friend Spallanzani, that the modern lavas on the east of Etna assume the prismatic form when they reach the sea; and regards this opinion as a mere illusion arising from the fissures common in amorphous lavas, and which may be equally observed in those that are inland. " I must therefore repeat," says he, "that the prismatic lavas around Etna, do not belong to the modern eruptions of that volcano, but to the ancient volcanoes under the ocean; and that modern lavas, whether on the land or in the sea, and under whatever circumstances, never pass into regular forms; but only appear in shapeless masses, or in such accidental shapes as arise from their site or refrigeration. Two or three prisms which I have found of modern lava near Mount. Finocchio, on the upland skirts of Etna, and some small ones in the clefts beneath, must, from their singularity, be ascribed to an accident, which can never establish a general system: and I am of opinion that to the same accident may be ascribed the two or four prisms, which

some naturalists have found in other modern lavas; and the great difference ought to be remembered between these scarce trifles, and the vast masses of prisms, groups of columns, and fascicular assemblages, of which even the fragments tend to regular divisions, which constitute their characteristic quality."*

Even the amorphous lava of the primeval period is very compact, sprinkled with filiform crystals of felspar, and some of siderite, with grains of chrysolite. That of Cape Passaro takes a beautiful polish. “The prismatic lavas are very hard and compact, and always of a dull ashy colour, or a bluish black; and I have never observed any pores in prismatic lava."† Among these primeval products is also found black or blue obsidian, sometimes in fragments, sometimes in tables in the slits of the lava, and sometimes concave,

* P. 144. He had before said, p. 112, "In generale posso dire che le lave prismatiche, le lave basaltine, i basalti, che sono intorno alla base dell' Etna appartengono agli ANTICHI VOLCANI, e non mai alle eruzione moderne di questo volcano."

† P. 176.