New South Wales. Sandstone formation. Embedded pseudo-fragments of shale. Stratification. Current-cleavage. Great valleys. Van Diemen’s Land. Palaeozoic formation. Newer formation with volcanic rocks. Travertin with leaves of extinct plants. Elevation of the land. New Zealand. King George’s Sound. Superficial ferruginous beds. Superficial calcareous deposits, with casts of branches. Their origin from drifted particles of shells and corals. Their extent. Cape of Good Hope. Junction of the granite and clay-slate. Sandstone formation. The “Beagle,” in her homeward voyage, touched at New Zealand, Australia, Van Diemen’s Land, and the Cape of Good Hope. In order to confine the Third Part of these Geological Observations to South America, I will here briefly describe all that I observed at these places worthy of the attention of geologists. NEW SOUTH WALES. My opportunities of observation consisted of a ride of ninety geographical miles to Bathurst, in a W.N.W. direction from Sydney. The first thirty miles from the coast passes over a sandstone country, broken up in many places by trap-rocks, and separated by a bold escarpment overhanging the river Nepean, from the great sandstone platform of the Blue Mountains. This upper platform is 1,000 feet high at the edge of the escarpment, and rises in a distance of twenty-five miles to between three and four thousand feet above the level of the sea. At this distance the road descends to a country rather less elevated, and composed in chief part of primary rocks. There is much granite, in one part passing into a red porphyry with octagonal crystals of quartz, and intersected in some places by trap-dikes. Near the Downs of Bathurst I passed over much pale-brown, glossy clay-slate, with the shattered laminae running north and south; I mention this fact, because Captain King informs me that, in the country a hundred miles southward, near Lake George, the mica-slate ranges so invariably north and south that the inhabitants take advantage of it in finding their way through the forests.