BRANNER: THE STONE REEFS OF BRAZIL. 169 
from the other rocks along the coast. A microscopic examination of the 
Rio 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 Élisée 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 tho 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. 
б. The partly choked up bays, such as Santos and Victoria. 
1 Élisée Reclus, Nouvelle géographie universelle. Tome XIX. Amérique du 
Sud, p. 146-147, Paris, 1894. 
