BRANNER : THE STONE REEFS OF BRAZIL. 93 



The outer reef is the largest, or rather the longest and most compact 

 of the three at this place. It is the Pratagy reef, properly speaking, and 

 lies across the mouth of the river, which flows north and south round 

 both ends of it. It has a width varying between eight and twenty 

 metres. 



The rocks of these reefs are quite hai*d and compact, and of a light- 

 brown color. 



One hundred and seventy metres south of the Pratagy reef is another 

 one of similar materials upon the beach. This one is about four hun- 

 dred metres long and seems to be a part of Lhe southward continuation 

 of the inner or beach reef exposed just north of the mouth of the river. 



The rock of this particular beach reef has a decided seaward dip, but 

 in addition the top of the reef is worn off so that the upper surface 

 itself has a seaward slope. 



Fig. 60. Section of the Rio Pratagy sandstone reef. 



This characteristic has been observed in several other of the rock reefs 

 of the coast. 



It is noticeable that these Pratagy reefs are not straight. 



Outside of the outer stone reef are two other parallel sets of reefs. 

 These reefs were not examined, but from their general appearance I 

 judge them to be coral reefs. The most distant one of these appears 

 to be aboixt one kilometre out from the beach and approximately parallel 

 to it. 



The stone reefs of Bahia. — I have visited the stone reefs of Bahia 

 several times, especially those at and near the lighthouse at the en- 

 trance to the bay, but I have not examined their full extent along the 

 coast to the east of the lighthouse. As is well shown in the accom- 

 panying illustration of these reef-rocks, the blocks about the lighthouse 

 have the appearance of having been undermined and broken into great 

 angular slabs. 



The Bahia reef is not exposed in a long beach-like line, as are most of 

 the other sandstone reefs. Here there has been no stream entering the 

 ocean from behind a bar, but the horizontal sand rock has been exposed 

 by the encroachment of the sea upon accompanying beds. The reef 

 appears to rest upon the edges of crystalline rocks. 



