2 VIEW OF THE FAUNA OF BRAZIL 



dip to the east. It rests upon a vast mass of talc slate, which 

 dips at an angle of 90° to the east, and forms the outermost 

 member in connection with the higher central range : and 

 farther from this principal chain, it alternates w^ith beds of 

 siliceous and clay slates. It often contains veins of quartz, 

 but I have never yet found in it any trace either of metals or 

 of organic remains. These limestone hills form smooth, 

 rounded ranges, which, however, have often a wild and pic- 

 turesque character, from the extraordinary disruption of their 

 masses, and the projection of their bare and steep walls of 

 rock. They are also clothed with a peculiar vegetation ; and 

 among the isolated outliers of this same formation, are nu- 

 merous lakes. Another physical phenomenon peculiar to the 

 limestone district, is the sudden disappearance of rivers (Su- 

 midouro), which again emerge at greater or less distances. — 

 This phenomenon arises from the number of fissures by which 

 the limestone is traversed, both above and below the surface. 

 Of the form of these fissures no universal description can be 

 given. Sometimes they appear as perpendicular clefts, run- 

 fiing in one direction ; sometimes they are intersected by a 

 number of transverse fissures; sometimes they run in zigzags ; 

 but often expand into passages, chambers, halls, and other 

 similar forms, in which breadth predominates. It is more 

 particularly this latter form of which I think it necessary to 

 give a more detailed description. 



The first thing that strikes the observer in these caves, is 

 the rounded form presented by them. The roof is arched, 

 and passes into the side walls by a regular curve. The floor 

 can seldom be seen ; but when visible, it exhibits the same 

 mode of junction with the sides ; and it is impossible to avoid 

 remarking, that all the angles which project at the different 

 divisions or bends of the passages, are in like manner rounded 

 oif. If we examine the walls and roof more carefully, we 

 perceive that the surface of the rock is full of protuberances 

 and hollows, blending into each other with the gentlest curv^e. 

 But especially do we observ^e numerous round holes, of all 

 sizes, both in the sides and roof, which penetrate more or less 

 deeply into the rock, and are closed at the bottom. Fre- 

 quently, where the walls project beyond the regular line, these 

 holes penetrate from one side to the other, and thus form pas- 

 sages, usually narrow, but sometimes large enough to admit 

 of our creeping through them, and presenting, on a smaller 

 scale,, the same phenomena already described in speaking of 

 the principal passages. 



The surface of the stone is moreover smooth, often to such 

 a degree as to reflect light : which circumstance, combined 



