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I. 



Introduction. 



There is no more striking geologic phenomenon along the eastern 

 shores of South America than the stone reefs of Brazil. 



These reefs are supposed by many persons to be of coral, and this error 

 has been propagated by writers of books of travels and by works on the 

 navigation of the south Atlantic. There are several reasons for this 

 error : coral reefs border many tropical coasts in a similar manner ; there 

 are extensive coral reefs on the coast of Brazil ; the stone reefs of Brazil 

 are unique, or rather they are found nowhere else in the world except 

 on a very limited scale ; seen from a vessel sailing along the coast or 

 even near at hand, the stone reefs are scarcely distinguishable from 

 coral reefs even by an expert ; and, finally, the sandstone reefs are 

 generally covered with calcareous growths common to coral reefs. The 

 only thing that is especially characteristic of the form of stone reefs 

 is their straightness, and this is not always apparent to one looking at 

 them either from the shore or from the ocean. In Brazil the only men 

 who really seem to know the dififereuce between the two kinds of reefs 

 are the lime-burners who make lime of the corals, and a few of the 

 masters of barca^as, or sugar boats. Among these men distinction 

 is made between the coral rock, which they know as j^edra de col (lime 

 rock), or as caber^a de carneiro (sheep's head, referring to Pontes and 

 oLher solid heads), and the sandstone which they call pedra de encantaria ; 

 that is, stone i.;sed for window and door sills and facings, as the reef 

 rocks have been used from the earliest times. 



In a sense the sandstone reefs are local, but the forces and agencies 

 that have formed them have been in operation along the entire coast, 

 from near Maranhao to southern Bahia, while local conditions have pre- 

 vented their formation at some places, or have favored their preservation 

 or destruction at others. 



The ports and towns behind the stone reefs owe everything to them. 

 Without these reefs there would be no Pernambuco, no Rio Grande do 

 Norte, no Porto Seguro, no Santa Cruz, to say nothing of the minor 

 ports like Rio Formoso, Serinhaem, Suape, Traigao, Mamanguape, and 



