PHYSICAL FEATURES OF MATTO GROSSO. 253 



Farther south, letween the sources of the Paraguay and those of the Ara- 

 guaya, and also between the Paraguay and the Parana, the uplands have been 

 eroded both on the east and the west, so that in some places the intervening 

 heights assume the aspect of real mountains, disposed in the direction frora north 

 to south. Such are the Serra de S. Jeronymo, and the Maracaju and Anham- 

 bahy ranges. Eruptive rocks, locally called basalts, have here cropped out above 

 the prevailing sandstones, and to their decomposition appears to be due a " red 

 earth " analogous to that which yields the coffee growers such splendid returns in 

 S. Paulo. 



Within the cirque-like space enclosed by the semi-circular range of heights, 

 the surface is broken by a number of rocky isolated masses, which are visible from 

 a great distance, and which are stratified with perfectly regular layers. The heights 

 themselves affect, for the most part, geometrical forms, as if vast slabs of rock 

 had scaled off, leaving smooth surfaces like the sloping sides of a finished pyramid. 

 The summits, as horizontal as if the ci"ests had been cut away by a sharp instru- 

 ment, correspond to other summits of like formation, so that all evidently at one 

 time formed part of a continuous terrace. 



From the disposition of the lines of disintegration round the flanks of the hills, 

 a conjecture may be hazarded as to the direction likely to be followed in the 

 process of destruction still going on. According to de Taunay, who resided 

 several years in the district, and traversed it in all directions, these sandstone 

 masses, with their perfectly regular horizontal series of stratification, consist of 

 lacustrine sedimentary matter sifted and distributed by the great freshwater lake, 

 which formerly covered the whole region. 



The detritus washed down from the surrounding slopes and escarpments has 

 also had its share in modifying the general aspect of the land. This detritus, 

 accumulating in the form of talus at the base of the hills, has been caught up 

 and redistributed by the running waters, in some places covering the ground 

 with fresh matter to a great thickness. Mountain masses formerly connected 

 with the inland plateaux and ranges, now appear completely isolated, because 

 their base is concealed by the accumulated débris, so that they rise abruptly 

 above the surface without any transitional talus formation. These isolated 

 masses, which have received the name of ifamhé, like the great mountain of the 

 serra d'Espinhaço, near Diamantina, shoot up in peaks and domes above the 

 surrounding woodlands, looking from a distance like colossal structures raised by 

 the hand of man. 



In the eastern districts of South Matto Grosso, the heights belonging to this 

 geological system are disposed in ranges or grouped in archipelagoes, standing 

 out above the sea of verdure. In the direction of the west they become con- 

 tmually less elevated and less numerous, or else appear completely isolated within 

 the circle of the horizon, though still extending in solitary groups all the way to 

 the right bank of the Paraguay, and even reappearing on the opposite side. As 

 already remarked by d'Orbigny, the Chiquito heights belong rather to this 

 Brazilian system than to that of Bolivia. 



