Page:Popular Science Monthly Volume 46.djvu/601

Rh with the red, yellow, and white products of the solfatara. But the richest volcanic colors are seen in a solfatara opening in an eminence on the outer and southern side of the volcano. An explosion has laid bare a vertical wall above a mysterious opening, and from this opening different gases have passed out and coated the walls with yellow, white, orange, red, and violet incrustations; these hues are remarkably bright and are enhanced by the setting of ebony which surrounds them.

"The inundations of lava poured out from a series of pits or bocche di fuogo situated in a line below the cone, on the rent from which escaped all that overflowed from Etna in 1886. They are empty monticles, which have the appearance of having been formed of burned coke. They are two, three, and ten metres high, and it is difficult to believe, on looking at them, that they could have given birth to this immense sea of lava which has climbed cones thirty to forty metres high, and which rises with a formidable hill in its middle.

"All this coke which we see is not lava, it is only slag. But this slag, these scoriæ, cover everything up, though it would not have been visible had there not been a deep excavation along the course of the lava stream, next to the pits. This great ravine, nearly a kilometre in length, thirty to fifty metres in width, and from four to twelve metres deep, with vertical walls, enabled us to see the internal structure of a lava stream. It is formed by the superposition of alternating layers of compact lava, a yard thick, with black ashes. In certain places we could count five or six layers, one over the other.

"It appears, then, that the lava stream, itself the result of the eruption, is formed of sheets of lava, which flow out one after the other and pass one above the other, each covering the scoriæ, or rather a part of the scoriæ of the surface of the preceding layer, without filling the interstices. But while layers of ashes or scoriæ only ten to twenty inches thick separate the lava layers, the sides and ends of the lava streams form great heaps of large pieces of loose coke, amid which one can detect the compact lava."

We had left our mules some distance down the mountain, and, while the guide went for them, as we were to return by a different route, I strolled about, enjoying the wondrously beautiful scene far below. A gentle sirocco was blowing, and far down beyond the fields of ashes and cinders a soft, delicate haze hung over the land of the vine and orange, and spread over the deep blue Mediterranean beyond.

We returned to Nicolosi in the hot afternoon sun, passing around by the south of Monte Rosso, skirting the right side of the eastern lava stream, whose entire length was about four miles, and whose rough, broken surface is so well represented by the