AVAILABLE DATA 



195 



Enormous areas of the country are also covered by dense and almost 

 impenetrable forests, and of these trackless regions, some of them larger 

 than the State of Pennsylvania, there are no maps whatever. 



Of a necessity the gathering of geologic information mider such cir- 

 cumstances is much more difficult than it is in a" country like North 

 America, where we have roads everywhere, railways never far away, and 

 most of our forests open to persons on foot or even on horseback, to say 

 nothing of the helpfulness of our excellent Land Office maps, even when 

 there is nothing better available. 



Furthermore, only two of the States, Sao Paulo and Minas Geraes, 

 have attempted geological surveys, and there has been a federal survey 

 only since 1907. With these important exceptions, there is, therefore, no 

 bureau of the government to which geologists, engineers, or the public 

 can turn for information about the geology of the country. 



These facts, and others that need not be mentioned, have led me to 

 value highly every bit of geologic information that has come to my knowl- 

 edge, no matter how small it may be ; indeed, much of the data has been 

 gathered from individuals and from all kinds of publications, scattered 

 far and wide, and many of them difficult or even impossible of access to 

 most people. 



But, as all human knowledge is imperfect and must, of a necessity, 

 remain so, the best we can do is to push forward little by little the fron- 

 tiers of our information, and, holding on firmly to such knowledge as we 

 have, add to it as opportunity offers. It is only so that science makes 

 progress in any country and in any field. In such spirit this map has 

 been prepared, for the purpose of showing the state of our knowledge of 

 the geology of Brazil and to prepare the way for additions to that knowl- 

 edge. 



The scale of the map makes it quite impossible to show many of the 

 details that are known of the geology of some regions, while so little is 

 known of other regions that the only safe thing to do is to leave the areas 

 blank until our knowledge shall have been extended. 



The geology shown on the map is based largely on personal observa- 

 tions covering a period of ten years of actual work and travel in all of 

 the Brazilian States except Goyaz and Piauhy. Much aid has been re- 

 ceived also from the unpublished notes of Eoderic Crandall, who was 

 some time my assistant and who did valuable work on the geology of 

 Bahia, Minas, Ceara, Alagoas, Sergipe, and Amazonas. This direct in- 

 formation has been supplemented by all the data published and by much 

 that is unpublished, but kindly furnished by friends and acquaintances 

 who have a personal knowledge of the geology of certain parts of Brazil, 



