Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/309

Rh surmounted all difficulties and seated ourselves on the highest ridge of the mountain. This uppermost region does not appear to contain in superficies more than an acre and an half, it is composed of a lava similar to that on its sides, though decomposed and changed white or grey by the action of the sulphurous acid; this acre and an half is itself a small crater, the walls of which are the different points on which we sat, and are plainly visible from below. Within, the lava is in the most rapid state of decomposition; losing its brown colour and shade of red, and acquiring a whitish grey almost the colour of chalk; large masses of sulphur are depositing, which are crystallized in minute though distinct forms; there is also a coating of alum produced by the union of the sulphurous acid with the argil of the lava; the surface is hot to the feet and the guides said it was dangerous to remain long in one spot; as it was, some of us sunk to our knees in the hot deposit of sulphur; upon striking the ground with the feet the sound is hollow, similar to what is produced by the same impulsion on the craters of Vesuvius and Solfaterra. I estimate the depth of the crater to be, from the highest ridge to the bottom, about 200 feet forming an easy and gradual descent, the whole being in a state of rapid decomposition, and charged with sulphur, large masses of which are every where depositing. I searched in vain, for any of the arseniate so common on Vesuvius, nor could I find those siliceous stalactites resembling strung pearls, which are met with in the island of Ischia, in the crater of the Solfaterra, and in the Maremma of Tuscany. The sulphur is pure and fine, and is sold for a considerable price at Orotava. We were not able to go all round the walls or exterior summit of the crater, and hence could not distinguish its southern or western declivity; M. Escolar assured me they are similar to, though more rapid than the side by

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