b J. C. BRANNER — STONE REEFS ON COAST OF BRAZIL 



and is entirely within the tropics, it appears to the casual observer that 

 it must also be a region of great rainfall. As a matter of fact the country 

 about cape Saint Roque and for hundreds of miles west, southwest, and 

 northwest of there is a region of devastating drouths. 



PERIODICITY OF THE STREAMS 



Ordinarily the rains fall during two or three months of the year, but 

 some years the annual rains do not come, and the dry season is drawn 

 out to an entire year, to two years, or even to five or six years. At such 

 times all vegetation away from streams is parched, the streams disappear, 

 cattle die of thirst, and sometimes the people themselves are compelled 

 to leave the region. When the rains do fall they are frequently torren- 

 tial, and the precipitation even in this region of drouth is in fact much 

 larger than at Para, and many other notoriously wet places. The result 

 of these conditions is that the streams of the region are strongly inter- 

 mittent, some of them being big enough to float an ocean steamer at one 

 time, and completely disappearing during the ordinary dry seasons, to 

 say nothing of years of severe drouths. 



The Rio Sao Francisco is the only large perennial river along this 

 entire strip of coast, and that river rises, not in the drouth region of north- 

 eastern Brazil, but about latitude 21 degrees south, far to the west and 

 south of the highlands of Minas Geraes and more than 1,000 miles from 

 its mouth. On the maps many other rivers are shown, to be sure, but 

 they are all more or less intermittent. Under such circumstances it fol- 

 lows that the intermittent streams flow boldly into the ocean only during 

 the season of rains, while during the dry season they become so enfeebled 

 that the waves of the ocean throw their own silts and the beach sands 

 back into their mouths, and in some cases complete barriers are thus 

 built between the land water and the sea water. These processes have 

 been in operation along the northeast coast of Brazil ever since the land 

 took on its present approximate form. 



CLOSED STREAMS 



'My studies of the stone and coral reefs have been carried on partly in 

 small boats and jangadas or rafts, but I have also walked several hun- 

 dred miles along the beach for the purpose of examining them and of 

 seeing their geographic and geologic surroundings. Naturally one trav- 

 eling along the beach would expect to find difficulty in crossing the 

 streams, but as a matter of fact during the longest trip made on foot and 

 at the end of the rainy season only two streams were found that could 

 not be waded in a distance of something over 200 miles. At the mouths 

 of several rivers there was connection between the ocean and the streams 

 only during high tide, and at several other places where streams were to 



