“To the eastward of Santa Cruz, the island appears perfectly barren. Ridges of hills run towards the sea; between which ridges are deep valleys, terminating at mountains or hills that run across, and are higher than the former. Those that run towards the sea, are marked by impressions on their sides, which make them appear as a succession of conic hills, with their tops very rugged. The higher ones that run across, are more uniform in their appearance. “In the forenoon of the 1st of August, after we had anchored in the road, I went on shore to one of these valleys, with an intention to reach the top of the remoter hills, which seemed covered with wood; but time would not allow me to get further than their foot. After walking about three miles, I found no alteration in the appearance of the lower hills; which produce great quantities of the _euphorbia Canariensis_. It is surprising that this large succulent plant should thrive on so burnt-up a soil. When broken, which is easily done, the quantity of juice is very great; and it might be supposed that, when dried, it would shrivel to nothing; yet it is a pretty tough, though soft and light wood. The people here believe its juice to be so caustic as to erode the skin[83]: but I convinced them, though with much difficulty, to the contrary, by trusting my finger into the plant full of it, without afterwards wiping it off. They break down the bushes of _euphorbia_, and suffering them to dry, carry them home for fuel. I met with nothing else growing there, but two or three small shrubs, and a few fig-trees near the bottom of the valley. “The basis of the hills is a heavy, compact, blueish stone, mixed with some shining particles; and, on the surface, large masses of red friable earth, or stone, are scattered about. I also often found the same substance disposed in thick _strata_; and the little earth, strewed here and there, was a blackish mould. There were likewise some pieces of slag; one of which, from its weight and smooth surface, seemed almost wholly metalline. “The mouldering state of these hills is, doubtless, owing to the perpetual action of the sun, which calcines their surface. This mouldered part being afterwards washed away by the heavy rains, perhaps is the cause of their sides being so uneven. For, as the different substances of which they are composed, are more or less easily affected by the sun’s heat, they will be carried away in the like proportions. Hence, perhaps, the tops of the hills, being of the hardest rock, have stood, while the other parts on a declivity have been destroyed. As I have usually observed, that the tops of most mountains that are covered with trees have a more uniform appearance, I am inclined to believe that this is owing to their being shaded.