branner: the stone reefs of brazil, 169 



from the other rocks along the coast. A microscopic examination of the 

 Eio Formoso reef rock shows that the sand is derived from granites or 

 gneisses, — just such rocks as lie to the landward of the narrow strip of 

 Tertiary sediments that form the immediate coast at that place. 



The theory of the transatlantic origin of the Brazilian sands seems 

 to have had some support from Elisee Reclus, who puts forward the 

 equally remarkable theory that the sediments swept into the Atlantic by 

 the Amazonas are deposited upon the coast of Georgia and the Carolinas.^ 

 In such a case the Amazonian silts would have to cross some of the deep- 

 est places in the Atlantic Ocean, to say nothing of the flocculating and 

 precipitating influence of salt-water upon these sediments. 



Conclusions regarding Coast Changes. 



1. There is no evidence of a perceptible change of level of the coast 

 since the discovery of Brazil. 



2. Changes have taken place in the form of the coast-line, and in the 

 adjacent streams, bays, and estuaries in historic times, but they are all 

 accounted for by the ordinary processes now in operation. 



3. The stone reefs are not metamorphosed or folded, and they do not 

 rise above tide-level, except in a few instances, where blocks have been 

 tilted by the undermining done by the waves. 



4. The coast lakes have been formed by the damming in of estuaries, 

 by the sands blown along the coast, and by the throwing back into the 

 estuaries of detritus cut by waves from adjoining headlands or brought 

 down by streams from the land. 



5. The straightness of the coast-line is due to the long period of wear- 

 ing to which the coast has been subjected, and to the constant on-shore 

 winds and waves along the coast. 



6. During the dry season the waves of the sea are able to close the 

 mouths of many of the weaker streams. 



7. At such times only the large streams are able to keep their mouths 

 boldly open. 



8. Although no changes of level are known to have taken place within 

 the historic period, there are evidences of both elevation and depression 

 of the Brazilian coast in late geologic times. 



9. The evidences of depression consist of : — 



a. The open bays : Rio de Janeiro and Bahia. 



h. The partly choked up bays, such as Santos and A'ictoria. 



1 fjlisee Kechis. Nouvelle gc'ograpliie universelle. Tome XIX. Amerique du 

 Sud, \\ 146-147, Paris, 1894. 



