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A memoir was then read "On the Geology of the Island of Juan Fernandez, in the Pacific Ocean, by Alex. Caldcleugh, Esq. F.G.S."

After a sketch of the past history and present state of this island, celebrated as the place of exile of Alexander Selkirk, the author proceeds to state that it is about twelve miles in length and four in breadth, possessing three ports, and consisting of very high land, the culminating point of which rises to about 3005 feet above the sea.

The author could discover no trace of a volcano said to exist here by former visitors; all the rocks, according to him, consist of basaltic greenstone and trap of various mineralogical structure, both amorphous and vesicular, together withtrappean concretions, no other contained minerals being observable except olivine and chaux carbonatée metas-tatique. It is further mentioned that the basalt in parts is almost columnar, and in others has a peaked and serrated outline, the mass being, here and there, traversed by dykes.

Owing to the peculiar character of this basalt, and especially from the great quantity of olivine, the author compares its age with that of the basalt of Bohemia, the Rhine, the Vivarrais, and Beaulieu in Provence.

After the ordinary business of the evening had been concluded, a Special General Meeting was held, when it was unanimously resolved, that the Session should terminate, for the future, on the first, evening of Meeting in June.