74 J. C. BRANNER — GEOLOGY- OK NORTHEAST COAST OF BRAZIL 



tains known as Coqueiro, Sao Jose, Catimbao, Quyri d'Alho, Andorinho, 

 and Chapeo are all of sandstone. These sandstones dip toward the 

 southeast at an angle of from 10 to 15 degrees. 



The sandstones contain mica, waterworn quartz pebbles, and bits of 

 kaolin. They yield some salt and saltpeter, which are extracted by 

 leaching, and certain organic substances the character of which was not 

 determined.* Doctor Lombard regards these sandstones as of "primi- 

 tive or pre-Cambrian '' age. 



In the absence of fossils it is hardly worth while to speculate on their 

 age. It seems much more probable, however, that these sediments be- 

 long to the great Cretaceous area that covers a large part of the interior 

 of Piauhy, Ceara, Parahyba, and Pernambuco. The elevation of the 

 Buique sandstones (between 800 and 900 meters above tide; appears to 

 make it improbable that they belong to the Tertiary. 



L, E. Dombre, a French engineer connected with the department of 

 public works of the province of Pernambuco, traveled through the in- 

 terior of that province in the years of 1874 and 1875, and in his letters 

 to the director' gave many valuable notes upon the geology of the region 

 visited.f 



Dombre went as far west as Floresta, but reference is here made only 

 to his notes upon on the geology in the vicinity of Recife ao Sao Fran- 

 cisco railway. 



Of the general character of the geology Mr Dombre says J that the few 



*This organic matter is known in the region in which it is found as borra. A sample of it was 

 given me' by Doctor Lombard, and was submitted to Dr J. M. Stillman, the head professor of 

 chemistry at Stanford University, who gives me the following as the results of his chemical ex- 

 amination : 



" The substance submitted under the name of borra appears to be largely earth, sand, and 

 gravel cemented together by or permeated with a substance or mixtux*e of substances of organic 

 origin and of deep chocolate brown color. The organic matter is of that class of substances 

 which have been at times called mineral resins — Erdharze — for want of more definite names. 



" The borra is brittle and hard, does not melt or soften appreciably by heating. At high tem- 

 peratures it gives off vapors of pungent odor and burns with a yellow flame, leaving an earthy 

 residue in the form of the original mass and composing by far the greater part of the entire mass. 

 Rubbed to a fine powder and extracted with alcohol and ether the borra gives a small quantity of 

 colorless extract of a bitter taste. The residue from the alcohol-ether extraction when treated 

 with caustic soda solution gives a solution of dark brown color, reprecipitated on neutralizing 

 with acids as a brown resinous mass, insoluble in water, and but slightly soluble in alcohol, to 

 which, however, it imparts a color by partial solution. That portion of the organic matter not 

 dissolved by hot caustic soda was in the form of a dark brown pulverulent mass mixed with inor- 

 ganic residue, and is not easily soluble in the common solvents. In concentrated sulphuric acid 

 it dissolves at least partly with a dark brown color. 



" My interpretation of the above is that the organic matter in the borra is a mixture of sub- 

 stances largely oxygenated and of faintly acid character, such as are often characterized as 

 ' mineral resins,' or as are intermediate between these and the so-called humus substances. The 

 organic matter is present in too small quantity and too difficult to separate from its earthy admix- 

 ture to be more definitely characterized." 



f Viagens do Engenheiro Dombre do Interior da Provincia de Pernambuco em 1874 e 1875 

 In French and Portuguese 12°, 86 pp. Recife, 1893. 



t Loc. cit., p. 36. 



