And here Lamarck, in spite of his uniformitarian principles, is strongly cataclysmic.

What he seems to have in mind is the great equatorial current between Africa and the West Indies.

To this perpetual movement of the waters of the Atlantic Ocean he ventures to attribute the excavation of the Gulf of Mexico, and presumes that at the end of ages it will break through the Isthmus of Panama, and transform America into two great islands or two small continents.

Not understanding that the islands are either the result of upheaval, or outliers of continents, due to subsidence, Lamarck supposed that his westward flow of the ocean, due to the moon's attraction, eroded the eastern shores of America, and the currents thus formed "in their efforts to move westward, arrested by America and by the eastern coasts of China, were in great part diverted towards the South Pole, and seeking to break through a passage across the ancient continent have, a long time since, reduced the portion of this continent which united New Holland to Asia into an archipelago which comprises the Molucca, Philippine, and Mariana Islands." The West Indies and Windward Islands were formed by the same means, and the sea not breaking through the Isthmus of Panama was turned southward, and the action of its currents resulted in detaching the island of Tierra del Fuego from South America.

In like manner New Zealand was separated from New Holland, Madagascar from Africa, and Ceylon from India.
He then refers to other "displacements of the ocean basin," to the shallowing of the Straits of Sunda, of the Baltic Sea, the ancient subsidence of the coast of Holland and Zealand, and states that Sweden offers all the appearance of having recently emerged from the sea, while the Caspian Sea, formerly much larger than at present, was once in communication with the Black Sea, and that some day the Straits of Sunda and the Straits of Dover will be dry land, so that the union of England and France will be formed anew.
Strangely enough, with these facts known to him, Lamarck did not see that such changes were due to changes of level of the land rather than to their being abandoned or invaded by the sea, but explained these by his bizarre hypothesis of westward-flowing currents due to the moon's action; though it should be in all fairness stated that down to recent times there have been those who believed that it is the sea and not the land which has changed its level.
This idea, that the sea and not the land has changed its level, was generally held at the time Lamarck wrote, though Strabo had made the shrewd observation that it was the land which moved.