AND RIO GRANDE DO NORTE, BRAZIL. 5 



a part of the division line between the states of Rio Grande do 

 Norte and Parahyba, is another mountain range. Beginning with 

 the Serras S. Miguel, Luiz Gomes, and Serra Padre, which mark 

 the meeting point of the three states, Parahyba, Rio Grande do 

 Norte, and Ceara, and stretching away in an easterly direction are 

 the Serras Negra, Barriguda, Furada, Patu, and other minor ones. 

 Between the end of this line and the northeast point of the Serra 

 Borborema, here called Serra Mattos, lies the Serra Joao do Valle. 



All of the mountains or tablelands thus far mentioned are more 

 or less similarly constructed, that is, they arise abruptly from the 

 surrounding plain, are usually flat-topped and are composed entirely 

 of crystalline rocks ; some of them have a core of granite. Other 

 than the more important serras whose names have been given there 

 are many small isolated peaks or serrotes of granite and gneiss 

 which rise irregularly and sharply out of a rolling, caatinga-covered 

 plain. 



There is one other type of mountain found in these states illus- 

 trated by the Serras Martins, Porto Alegre, and Joao do Valle. The 

 Serra Joao do Valle I did not visit but saw from a distance. Mr. 

 Roderic CrandalP describes it as being of the same structure as the 

 others named. These serras represent an unusual phenomenon. 

 They rise abruptly from the plain of Rio Grande do Norte, to 

 an elevation of about 700 meters and their summits are remarkably 

 flat-topped. The bulk of the mountains are composed of crystal- 

 line rock, nearly all schist with some gneiss, as is also the surround- 

 ing country. But their summits are capped with sandstone, about 

 50 meters thick. These three mountains, in so far as I have been 

 able to determine, are peculiar in this respect. 



Drainage. 



The drainage everywhere in Parahyba and Rio Grande do Norte 



flows to the east or northeast ; in other words it takes the shortest 



course to the sea. Along the southern border of Parahyba the 



watershed marks the boundary between that state and Pernambuco. 



3 Roderic Crandall, " Geographia, geologia, supprimento d'agua, trans- 

 portes, e agudagem," page 6, Rio de Janeiro, 1910. 



