Chapter V—Galapagos Archipelago.

Chatham Island.—Craters composed of a peculiar kind of tuff.—Small basaltic craters, with hollows at their bases.—Albemarle Island; fluid lavas, their composition.—Craters of tuff; inclination of their exterior diverging strata, and structure of their interior converging strata.—James Island, segment of a small basaltic crater; fluidity and composition of its lava-streams, and of its ejected fragments.—Concluding remarks on the craters of tuff, and on the breached condition of their southern sides.—Mineralogical composition of the rocks of the archipelago.—Elevation of the land.—Direction of the fissures of eruption.