BRANNER: THE STONE REEFS OF BRAZIL. 5 



many others where the sugar boats load and take refuge along the whole 

 coast from southern Bahia to Ceara and Maranhao. 



The geological and geographical peculiarities of these stone reefs con- 

 sist in the facts that — 



I. They are of sand consolidated to a hard — in places almost 

 quartzitic — sandstone. 



ir. They stand about flush with the water at high tide, while at lovv 

 tide they are left exposed like long, low, flat-topped walls, with a width 

 of from five metres to one hundred and fifty metres, and a length of 

 from a few paces to several kilometres. 



III. They accompany the shore line with many and great interrup- 

 tions from north of Ceara to Porto Seguro, a distance of two thousand 

 kilometres. 



IV. With unimportant exceptions the reefs do not occur along the 

 Brazilian coast beyond these limits. 



V. They usually stand across the mouths of streams and estuaries 

 forming perfect natural breakwaters for the small harbors behind them. 

 Sometimes they follow the shore, either on the beach or at a short 

 distance from it. 



VI. They are all nearly straight. "When crooked, their curves are 

 gentle. 



VII. The structure and position of the reefs and the animal remains 

 they contain show that they have been made by the lithification of 

 beach sands in place. 



VIII. When stone and coral reefs occur together, the stone reefs are 

 inside or landward of the coral reefs. It is possible, however, that there 

 may be buried coral reefs in some cases to the landward of some of the 

 stone reefs. 



IX. The coral reefs are now growing over and upon the stone reefs in 

 some places, while at other places there are stone reefs overlying dead 

 coral reefs. 



X. In general appearance, elevation, and position the sandstone reefs 

 bear a striking resemblance to the coral reefs. 



My work on the reefs was begun in 1875-6-7, while I was a member 

 of the Commissao Geologica do Brazil ; it was extended at subsequent 

 visits in 1881-2-3, and ended in June, July, August, September, and 

 October, 1899, when an opportunity was afl'orded me by Dr. Alex- 

 ander Agassiz to finish it. This last visit has been of the utmost 

 importance, for I have thus been able to revise earlier and less trust- 

 Avorthy observations, to visit new localities, and also to study the prob- 



