434 JENKINS— GEOLOGY OF THE [May 29. 



sand at the points, forming a smooth straight shore Hne up to the 

 south side, and leaving a Httle cove on the north side. Tall cocoanut 

 palms may grow along the shores of this cove, waving over a tiny 

 fishing village and a little church. The fishermen can here embark 

 in their jangadas with greater ease than out on the windy south side 

 of the point. Usually into such a cove a stream flows, if not, the 

 people get their water by digging into the sand of the coast and a 

 bubbling supply of sweet water is easily obtained. Sometimes one 

 may see fresh water coming up through the sand right where the 

 waves wash. 



The sand is blown into the river mouths and tends to fill up 

 their south sides, causing the streams to cut into their northern 

 banks, where the sand is being swept away. Thus many of the 

 streams turn, just before reaching the sea, and flow northward as 

 they enter the sea. A view of a river's mouth from a vessel at sea 

 shows a high range of sand-dunes on the south side, while to the 

 north the country is low and rises gradually farther up the coast, 

 where it culminates at another river mouth. 



Fig. I. A view from a steamer towards a river mouth, showing how the sand 

 piles up at the south side of the stream. 



There is often a hardened sand-beach in front of the mouth of 

 such a stream, lying in a straight line parallel to the shore, where 

 the fresh water meets the sea water. These stone reefs^ have the 

 general appearance of an ordinary sand bar, but they are hardened 

 almost to a quartzite, and are difficult to break with the hammer. 

 They contain white quartz sand and marine shells now found along 

 the beaches. Often these stone reefs are found with no apparent 

 stream behind them, but if one goes farther back into the country 

 one may find an abandoned stream channel which formerly had an 

 outlet behind the stone reef. 



ij. C. Branner, "The Stone Reefs of Brazil," Bid. Mus. Comp. Zool, 

 Geol. Ser., VII., Cambridge, 1904. 



