Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/301

Rh ash and pumice eruption of Vesuvius and Ætna. The bed of soil is here very deep. I examined some ravines that the rains had laid open to the depth of 30 or 40 feet: the strata were indurated at the bottom, and resembled the tufa in the vicinity of Naples, and all contained the substances mentioned above. This tufaceous character changes as you ascend the hill that separates Laguna from Santa Cruz; the hill itself, and the whole neighbourhood of the latter city is one continued stream of lava, hardly at all decomposed, with little or no vegetation; but here and there in the hollows some few stunted plants of the aloe algarvensis, and the cytisus.

Having given a general account of the island, I shall now attempt to describe the country of the peak, which mountain ascended on the 16th of September, 1810. The road from Puerto Orotava to the city of Orotava, is a gradual and easy slope for three or four miles, through a highly cultivated country. The soil is composed of volcanic ash and earth, and to the eastward of the town of Puerto di Orotava are the remains of a recent volcano, the crater and cone being distinctly visible. Leaving the town of Orotava, after a steep ascent of about an hour through a deep ravine, we quitted the cultivated part of the slope or valley, and entered into a forest of chesnuts; the trees are here of a large size. This forest of chesnuts is mixed with the erica arborea, or tree heath, which shrub rises to the height of 18 or 20 feet. Some of the stems are as thick as the arm of a man, joined together in bunches or tufts like the common heath. The form of this forest is oblong, it covers the flank of those hills which I have already denominated the central chain, from their summit to half their elevation from the plain. The soil here is deep, and formed of decomposed lava, small ash, and pumice. I examined several channels in the strata or ravines

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