But instead of being hard, as Silurian rocks are wont to be, they are mere loose beds of dark sand and shale, yellow with sulphur, or black with carbonaceous matter, amid which strange flakes and nodules of white quartz lie loose, ready to drop out at the blow of every wave.

The strata, too, sloped upward and outward toward the sea, which is therefore able to undermine them perpetually; and thus the searching surge, having once formed an entrance in the cliff face, between what are now the two outer points, has had nought to do but to gnaw inward; and will gnaw, till the Isle of Monos is cut sheer in two, and the 'Ance Biscayen,' as the wonderful little bay is called, will join itself to the Ance Maurice and the Gulf of Paria.

In two or three generations hence the little palm-wood will have fallen into the sea.

In two or three more the negro house and garden and the mangrove swamp will be gone likewise: and in their place the trade- surf will be battering into the Gulf of Paria from the Northern Sea, through just such a mountain chasm as we saw at Huevos; and a new Boca will have been opened.
But not, understand, a deep and navigable one, as long as the land retains its present level.

To make that, there must be a general subsidence of the land and sea bottom around.