This geographic district in the State of Matto Grosso is indifferently called the cordillara of Parecys, but does not present a mountainous aspect except on the South side. On this scarred side, the rock is cut into peaks, or cut away into obelisks. On the other side towards the Tapajóz and Xingú, a long range extends and gradually declines into the plains of the State of Amazonas. D’Orbiguy found in the high northern part of Matto Grosso, the existence of beds pertaining to the carboniferous age and corresponding to rocks of the same nature which on the opposite side of that region are found in the Bolivian bases of the Sierra of Santa Cruz. After this Hart and Derby verified the fact that the southern parts of the Araxá, which are the elevated borders of the tableland, date probably from paleozoic epochs, and there are found the carboniferous, devonian and silurian beds. Fossil beds found by the Geologist Smith below the hillocks of the plains, 50 kilometers east of Cuyabá, place these facts beyond doubt. More to the North is the zone of the rocky places, which in links cut the Madeira, Tapajóz, Xingú, Tocatius and their tributaries, the walls denuded by erosion, are all of the crystalline formation, granite, gueis, porphory and quartzite. The elevations that unroll in the direction of the South, between the sources of the Paraguay and Araguaya, following between the Paraguay and the Paraná, do not present the same characteristics as the tablelands of the North. The high parts of Western Matto Grosso were separated from the East and West sides and devastated by lateral excavations, take in certain places the aspects of true mountain chains, and for this reason they are named, from the North to the South, the Sierras of S. Jeronimo, Maracajú and Anhauhaly. Eruptive rocks, called basaltic in this country, probably porphyritic rend the beds of sandstone, of which the mountains are composed and appear to form by their disintegration “red lands,” similar to those which give the farmers of S. Paulo their abundant harvests of coffee. In a sort of circle limited by a semicircle of elevations isolated masses have been lifted up, rocks whose outlines, seen from a distance, have a perfect regularity. The hills proper, for the greater part, have geometrical forms, which it should be said, great forces have crumbled, leaving smooth walls like the sides of pyramids. The tops of the tablelands, as well as summits, have been maimed by a force certainly corresponding to the other summits, which now may be seen as part of the same prairie. According to Taunay, who traveled over the country, these masses of sandstone in horizontal beds regularly placed one above another, are formed of marshy sediment deposited by the sea of fresh water, which in former times covered this region. [Illustration: COLLECTING THE LATEX.]