Down, however, we went, by a natural ladder of Matapalo roots, and saw at once how the cove was being formed.  The rocks are probably Silurian; and if so, of quite immeasurable antiquity.  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.  For surf, when eating into land, gnaws to little deeper than low-water mark:  no deeper, probably, than the bottoms of the troughs between the waves.  Its tendency is—­as one may see along the Ramsgate cliffs—­to pare the land away into a flat plain, just covered by a shallow sea.  No surf or currents could nave carved out the smaller Bocas to a depth of between twenty and eighty fathoms; much less the great Boca of the Dragon’s Mouth, between Chacachacarra and the Spanish Main, to a depth of more than seventy fathoms.  They are sunken mountain passes, whose sides have been since carved into upright cliffs by the gnawing of the sea; and, as Mr. Wall well observes, {117} ’the situation of the Bocas is in a depression of the range, perhaps of the highest antiquity.’

We wandered along the beach, looking up at a cliff clothed, wherever it was not actually falling away, with richest verdure down to the water’s edge; but in general utterly bare, falling away too fast to give root-hold to any plant.  We lay down on the black sand, and gazed, and gazed, and picked up quartz crystals fallen from above, and wondered how the cove had got its name.  Had some old Biscayan whaler, from Biarritz or St. Jean de Luz, wandered into these seas in search of fish, when, in the beginning of the seventeenth century, he and his fellows had killed out all the Right Whales of the Bay of Biscay?  And had he, missing the Bocas, been wrecked and