The southern point of South America, south of the Rio Negro, as far as the Straits of Magellan, known as the plateau of Patagonia, is a true table-land of from 1200 to 1400 feet in height. It is composed of ragged strata of porphyry or of vast lava-masses, and has been explored by Captain Fitz Roy, in 1837, from the mouth of the Santa Cruz River to the snow-capped Andes in the west. The plateau diminishes gradually in elevation from west to east, till it touches the sea line. In North America the broad plateau extending through Northern Texas and the Indian Territory, and lying on both sides of the Arkansas River, increases in elevation gradually from St. Louis, on the Mississippi, less than 500 feet above the sea, to Santa Fé, on the upper course of the Rio Bravo, 7000 feet above the sea. It ascends so slightly that the rise is imperceptible to the eye, the broad plains there taking the name of prairies. St. Louis is 420 feet in absolute elevation; the eastern Arkansas plateau 1500 to 3000 feet; the high western Arkansas table-land from 3000 to 7000 feet, where, at the point of greatest altitude, lies the City of Santa Fé, in the Territory of New Mexico, 7047 feet above the sea. This broad, sloping tract reaches out to a great extent at the north, crossing the Missouri, and embracing the colossal North American lakes. Lake Huron and Lake Michigan, about 578 feet deep, and Lake Superior, 627 feet deep, lie in vast hollows in that great continuous plateau, which extends into the British Possessions, rises again to 800 or 1000 feet in elevation, and is rocky and craggy, yet not enough so as to take the name of a mountain chain, but simply to form a clearly-marked water-shed, which Fremont and Nicollet have measured. In Australia and Europe plateaus of the second grade of elevation are not wanting. In Australia, however, they are limited to the triangular district in the southeast, which has become the place of settlement for the chief English colonies, and which, bearing the name of King’s Table-land, rises to a height of 2500 feet, and occupies the largest area of all the Australian table-lands. In Europe this physical feature is displayed most distinctly in the Spanish plateaus, which occupy by far the largest proportion of the entire peninsula. Madrid lies on one of these plateaus, at a height of 2100 feet, five times as high as Paris, on the Seine, and as high as Innspruck, in the very heart of the Tyrol; Toledo, in the valley of the Tagus, is 1734 feet above the sea. The average elevation of New Castile, the central part of Spain, is 2000 feet. Old Castile, which borders it on the north, separated from it by the Guadarrama ridge, is about a thousand feet higher. Burgos, in the center, is 2700 feet above the sea; Segovia, to the south, 3100 feet. The average elevation of Old Castile is 3000 feet.