374 G. A. Waring — Reef Formations of the 



by calcareous material. It is pale yellow in color and is pos- 

 sibly an example of recent cementation, though it does not 

 closely resemble the more typical reef north of the stream's 

 mouth. Rio do Fogo has only a slight flow during the dry 

 season, and at present does not support a growth of mangrove ; 

 but a bed of black clay exposed in the beach near its mouth 

 resembles the material of mangrove swamps. The relative 

 positions of the stream mouth, the bed of clay and the typical 

 reef to the north suggest that the stream formerly entered the 

 ocean somewhat farther north, while the wide reef of calcareous 

 sandstone to the south suggests that more recently its water 

 may have sought the ocean in that direction. Sand dunes now 

 crowd the stream channel back from the shore and absorb 

 most of its water, which reappears in part nearer the beach in 

 the form of small springs. 



Two miles north of Rio do Fogo, large slabs of the typical 

 rock are exposed at low tide, lying upon iron-cemented sands 

 at a small point near the village of Peroaba, while two reef 

 fragments 200 or 300 yards long are seen respectively 1-| 

 and If miles northward, at about half-tide level, partly 

 buried in the beach. 



Continuing along the beach, a few other masses of the rock 

 are to be seen in several places firmly cemented to red, iron- 

 cemented sandstone that forms fringe reefs, but the next 

 typical reef is met near Ponta Reducto, a number of miles 

 farther to the northwest. The rock here appears abruptly in 

 the surf and owing to the slight curve of the shore soon 

 reaches the beach. Thence the reef rock extends along the 

 beach, in large part as broken slabs piled up beyond ordinary 

 high-tide level, for a distance of If miles, to the southeastern 

 end of the point, where at low tide it is seen to be firmly 

 cemented to the red sandstone at the base of the bluff. In the 

 cove beyond the point a few slabs of the rock appear, and 

 again at a wide curve of the low beach 1-J- miles farther 

 northwest. Xear the next curve of the beach, one mile beyond, 

 the material appears on the shore above high tide, extends 

 along the upper border of the beach as a succession of broken 

 slabs, and disappears beneath a small sandy point. It reappears 

 on the other side of this point, however, and continuing partly 

 in the water but mainly along the upper part of the beach, it 

 finally disappears landward (fig. 3d). The total length of this 

 reef, including the portion hidden by the sandy point, is fully 

 3 miles. 



The calcareous sandstone is next seen 5 miles westward, at 

 a place called Queimadas. Here from an inward curve of the 

 beach line, a narrow reef extends into the water for perhaps 

 300 yards. It appears for a few yards on shore as a confusion 



