BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 7, pp. 255-314, PLS. 10-14 FEBRUARY 4, 1896 



DECOMPOSITION OF ROCKS IN BRAZIL 



BY JOHN C. BRANNER 



{Read before the Society August 28^ 1895') 

 CONTENTS 



Page 



Introduction 256 



Evidences and results of decomposition 256 



Decay in place 256 



General distribution and character of the decomposition 256 



Areas studied and their characteristics 257 



Absence of decomposition 265 



Land-slides .... 266 



Talus and its decomposition 268 



Exfoliation 269 



In general 269 



Exfoliation of peaks , . . . 269 



Exfoliation of boulders 277 



Fluting 280 



Agencies of decomposition 280 



Mechanical agencies 281 



General discussion 281 



Temperature and disintegration 282 



Range of temperature 284 



Temperature and exfoliation 285 



Color as related to decay 293 



Texture as related to decay 293 



The cause of fluting 294 



Organic chemical agencies 294 



General discussion 294 



Burrowing animals 295 



Ants 295 



Termites 298 



Chemical work of plants 300 



Supposed work of bacteria 303 



Inorganic chemical agencies 304 



Carbonic acid (CO.^) 304 



Nitric acid (HNO3) 306 



XXX— Bull. Geol. Soc. Am , Vol. 7, 1895. (255) 



