1913-] REGION ABOUT NATAL, BRAZIL. 455 



hardness but usually rather unconsolidated. The amount of iron 

 in the rocks seems to determine their color and also their hardness. 

 These colors vary from white through all sorts of shades, especially 

 red, brown, purple and yellow. Sometimes they are banded or 

 streaked. Sometimes, as at Barreiras do Inferno, certain beds have 

 concentrated all the iron. At this place the undermining action of 

 the waves causes huge iron-sandstone blocks to break off and drop 

 from a ledge three meters thick and these form a pile of irregular 

 shaped boulders along the coast, all cemented together. These 

 cliffs extend for about a kilometer along the coast. Their maximum 

 height is twenty-five meters and they are perpendicular or sometimes 

 overhanging. It is very difficult to pass back of them on account 

 of the deep ravine structure formed there. 



Just south of Barreiras do Inferno there are caves formed in 

 the sandstone, which is harder and stands up better than in other 

 places. These caves are formed by the waves at high tide. One 

 cave was noticed which was one meter high, seven meters wide, and 

 ran back five meters into the rock. 



Usually the sandstone bluffs are not much over five meters high 

 and the bedding is invisible on account of the peculiar banded per- 

 pendicular leaching. This was especially noticed at Morcego and 

 at Pirangy. Here the iron is concentrated in perpendicular bands 

 or columns, leaving a soft sandy or putty-like material in between. 

 Over these bluffs the sand-dunes rest. Probably the rain, which 

 sinks down through the sand-dunes, is regulated in seepage in such 

 a way as to have this peculiar leaching effect on the beds below. 



Farther into the country this sandstone series is easily recognized 

 by its peculiar reddish color, visible especially along the low bluffs 

 which border the wide valleys. Also it is seen where the wind- 

 blown sand is only thinly scattered over the surface of the ground. 



In all these beds not a single sign of any organic remains was 

 found. 



The vegetation on this series is always poor, scanty, and scrubby 

 in form, sometimes almost entirely lacking. 



