Chapter 18

Rio Negro.—S. Josef.—Port Desire, white pumiceous mudstone with infusoria.—Port S. Julian.—Santa Cruz, basaltic lava of.—P. Gallegos.—Eastern Tierra del Fuego; leaves of extinct beech-trees.—Summary on the Patagonian tertiary formations.—Tertiary formations of the Western Coast.—Chonos and Chiloe groups, volcanic rocks of.—Concepcion.—Navidad.—Coquimbo.—Summary.—Age of the tertiary formations.—Lines of elevation.—Silicified wood.—Comparative ranges of the extinct and living mollusca on the West Coast of S. America.—Climate of the tertiary period.—On the causes of the absence of recent conchiferous deposits on the coasts of South America.—On the contemporaneous deposition and preservation of sedimentary formations.