1913-] REGION ABOUT NATAL, BRAZIL. 433 



The ways by rail afforded the gathering of geological data by 

 notes taken from the car windows, and by material collected at 

 the various places where the train stopped. At certain points the 

 party remained for several days and from these points horseback 

 trips and walks gave data of more detailed character. These side 

 trips were made around the towns of Taipu, Itapasaroca, Ceara- 

 Mirim, and Extremoz. 



A horseback trip from Carnahubinha to Macahyba and back 

 into the interior, followed one of the contacts and gave familiarity 

 with the general character of the country. 



Thus the map was compiled from compass traverses, notebook 

 sketches, railroad surveys, hydrographic charts, and the map of 

 the region made by Crandall and Williams to the scale of i to 

 1,000,000. 



Topographic Relief. 



The Coast. 



The vast stretches of sand are the most striking feature in the 

 region about Natal and the northeastern coast of Brazil. The wind 

 blows constantly up the coast to the northwest, driving the sand 

 before it, filling up the stream mouths, banking against the low 

 shrubs, sometimes planted by the people along the coast, forming a 

 great range of sand-hills parallel to the coast. It is swept back by 

 diverging currents over the low interior country for many kilometers 

 covering up the soil ^d rocks, filling up the broad valleys, and 

 forming long parallel sand-dunes all pointing to the northwest. 



Underlying sandstones outcrop along the coast at various points. 

 They form generally perpendicular cliffs from a few feet to about 

 seventy-five feet in height as those of Barreiras do Inferno. These 

 sandstones contain iron which is concentrated in certain places, 

 hardening them into limonitic rocks that ring like steel when struck 

 with the hammer. Sometimes all the pebbles of a portion of a 

 beach are cemented together in this manner, forming a prominent 

 point along the coast. These low points of dark, red-brown rocks 

 and parti-colored cliffs of sandstone break the continuity of the 

 white sand beaches. The wind, sweeping up the coast, banks the 



