THE 



AMERICANJOURNALOFSCIENCE 



[FOURTH SERIES.] 



Art. XXX. — Reef Formations of the Northeast Coast of 

 Brazil • by Gerald A. Waring. With Plate IX. * 



Location and character of the region. 

 Calcareous sandstone. 

 Eeefs. 



General features. 

 Mode of formation. 

 Eeefs north of Rio Grande do Norte. 

 Other occurrences of calcareous sandstone. 

 Iron-cemented sandstoue. 

 Cliffs. 

 Eeefs. 

 Coral reefs. 

 Summary. 



Location and Character of the Region. 



Lying wholly within the tropic zone, northeastern Brazil 

 forms the shoulder of the South American continent, To the 

 northwest is the Amazon region, noted for its abundant rains 

 and tropic vegetation. To the south also the country is well 

 supplied with water ; but the region between about 3 and 15 

 degrees S. lat. is arid and is subject to periods of great drought. 

 Few rivers drain this area, and except for a narrow belt along 

 the coast, water is scarce during the greater part of the year. 

 All of this coastal extent is low. For many miles the shore is 

 bordered by sand dunes, which extend back a few miles to a 

 gently rising plain, covered with a stunted forest of tall brush 

 and cactus, and interrupted here and there by small isolated 

 peaks and mountains. There are few settlements other than 

 fishing villages along this barren stretch of coast. Nearly all 

 the streams that enter the ocean discharge water only during 



* The writer is indebted to Dr. J. C. Brainier for encouragement in the 

 preparation of this article. 



Am. Jour. Sci.— Fourth Series, Vol. XXXVII, No. 221.— May, 1914. 

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