branner: the stone reefs of brazil. 87 



are no indications of a northward continuation of it, unless they be 

 in the sunken rocks further out, and over which the waves break at low 

 tide. These breakers lie in the axis of the stone reef. 



There is a coral reef off shore at Praia da Gamella also in the axis of 

 the stone reef ; possibly it is built upon a base of sand rock. 



The outer or northern end of the stone reef is covered with barnacles. 

 A coral reef beginning here on the east side of the rock reef bends back 

 toward the south, and, being separated from it by a channel, protects it 



Fig. 54. Longitudinal section of an undermined portion of the stone reef, 



Rio Fornioso. 



from the force of the waves of the open ocean. It is only at their out- 

 ward or northern ends that these two reefs are joined ; the channel sep- 

 arating them becomes wider and wider till it passes the Barreta das 

 Jangadas, and at this end it is more than a hundred metres in width. 

 This channel has a bottom of coarse calcareous sand with very fine mud 

 in some places. Corals and other organic calcareous growths have 

 spread over the outer side of the sandstone reef, and in many places 

 have grown upon the stone reef as a base until they are now near the 

 surface of the water. 



It is noticeable that we here have corals thriving in front of a river 

 mouth. The fact is that the stream is deflected to the north by the 



Fig. 55. Across Rio Formoso stone and coral reefs. Tlie darker portions are corals. 



stone reef which thus protects the corals from the mud and fresh water 

 entering from the river. A similar state of affairs is found at several 

 other places along this coast. 



From the land end of the stone reef, following southward along the 

 sandy beach to a distance of eighteen hundred metres, there is another 

 (or the same) stone reef joined to the land and running out into the 

 embayment so as to make an angle of about twenty degrees with the 

 beach. This reef is about seventy metres wide. Just where it joins 

 the bead) the rock is the coarsest seen in this vicinity, the pebbles 

 being as big as pigeon's eggs. The piece is only short, being about 



