The rock among these mountains, as I have said already, is very seldom laid bare.

Decomposed rapidly by the tropic rain and heat, it forms, even on the steepest slopes, a mass of soil many feet in depth, ever increasing, and ever sliding into the valleys, mingled with blocks and slabs of rock still undecomposed.

The waste must be enormous now.

Were the forests cleared, and the soil no longer protected by the leaves and bound together by the roots, it would increase at a pace of which we in this temperate zone can form no notion, and the whole mountain-range slide down in deluges of mud, as, even in the temperate zone, the Mont Ventoux and other hills in Provence are sliding now, since they have been rashly cleared of their primeval coat of woodland.
To this degrading influence of mere rain and air must be attributed, I think, those vast deposits of boulder which encumber the mouths of all the southern glens, sometimes to a height of several hundred feet.

Did one meet them in Scotland, one would pronounce them at once to be old glacier-moraines.