Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/303

times in deep ravines, gradually rose in height till the summits were lost in those of the central chain, while on our right we were rapidly gaining an elevation above the lower range of the peak. This range forms one flank of the plain or valley of Oratava, stretching from south-east to north-west, and is broken into steep precipices, cut down in some places perpendicular to the horizon, and called las Horcas: it joins the central chain at the high elevation of the pumice plains, sweeps down the side of the valley, and forms a headland near 200 feet high, projecting into the sea, some miles from Oratava; we traversed this country an hour or two, till we reached the point of intersection of las Horcas with the plains of pumice. On the road are several small conical hills or mouths of extinct volcanoes, the decomposed lava on the edges of these craters having a strong red ochreous tint; by degrees the lava becomes more and more covered by a small ash, and the masses or heaps of pumice gradually increase, till the surface is completely concealed. At length an immense undulated plain spreads itself like a fan, on all sides, nearly as far as the eye can reach, and this plain is bounded on the west south-west, and south south-west, by the regions of the peak; and on the east and north-east by a range of steep perpendicular precipices and mountains, many leagues in circumference, called by the Spaniards Las Faldas. M. Escolar informed me that the wall could be traced for many leagues, the whole circumference of which evidently formed the side of an immense crater. This tract, called Las Canales, contains, according to the same authority, 12 square leagues. As we entered this plain from the south-west, there are to be seen several declivities of lava and strata, broken inwards towards the plain, and evidently a continuation of the above mentioned line of wall and the remains of the original crater. There