ashes and volcanic sand. Even before we reached the pine-forest there was evidence of the action of water, which had covered the slope of the mountain with beds of thick compact tufa, composed of these lapilli mixed with fragments of lava. The water-courses had cut deep channels through these beds, and down into the rock below; so that the streams from the melted snow rushed down between walls of lava, in which traces of columnar structure were observable.
The snow we had travelled over was sometimes dry and powdery, and sometimes hard and compact. There were no glaciers, and no glacier-ice, properly so called. It never rains at this elevation; and, though evaporation goes on rapidly with half the pressure taken off the air, and a great increase in the intensity of the sun’s rays, the snow either passes directly into vapour, or carries the water off instantaneously, as it is formed. Only so much water seems to be produced and re-frozen as suffices to make the snow hard, and in some favourable places near the rocks to form lumps of ice, and some of those great icicles which the Spaniards brought down from the mountain on their first expedition, so greatly astonishing their companions.