Northeast Coast of Brazil. 387 



the city itself irregular masses of the material several feet thick 

 are exposed in low bluffs near the harbor, a short distance 

 above tide level. The material was also encountered at ap- 

 proximately sea level in nearly every one of about 50 wells 

 that had been drilled in the upper part of the city prior to 

 1913 ; but so far as could be determined by examination of the 

 well records, the material is thinnest in the wells most distant 

 from the harbor. It was not encountered in wells sunk in the 

 lower part of the city (below the exposures in the bluffs) ; 

 neither was it met in a well sunk in the lowland across the 

 harbor channel,* nor in excavations made to depths of more 

 than 50 feet in the channel itself for the piers of a railroad 

 bridge. At the farther side of a wide flat across the harbor 

 from Natal the hard, iron-cemented material is exposed near 

 the base of a red sandstone bluff, but a bed which appears to 

 be a continuation of the material exposed in the bluff is seen 

 to thin out landward, along a railroad cut which ascends the 

 slope. About 20 miles south of Natal, in bluffs bordering a 

 tidal inlet or lagoon, broken masses of the iron-cemented sand- 

 stone show the presence of a layer 2 or 3 feet thick, but on 

 tracing it inland by occasional fragments along a railroad cut, 

 their decreasing size indicates that the hardened layer rapidly 

 thins. 



A few miles east of Fortaleza much indurated iron-sandstone 

 is exposed on the shore as low bluffs and fringe reefs. About 

 1\ miles inland the material was encountered in a well at 

 a depth of 6 feet, which well was continued to a depth of 16 

 feet without passing through it. This well is 300 yards from 

 the margin of a tidal lagoon. The material is also exposed in 

 a pit 100 yards nearer the lagoon, at a depth of only 2 feet, 

 and although it was not found along the border of the lagoon, 

 springs of fresh water issue a few feet above the margin, prob- 

 ably from about the upper surface of the impervious material. 



The eastern side of the harbor of Camocim is bordered by 

 large sand dunes that are continually encroaching on the water 

 and effectually cover the underlying formation. To the west, 

 however, the immediate coast is low, though backed by dunes, 

 and is bordered for several miles by a nearly continuous reef 

 of iron-cemented sandstone. Springs of fresh w T ater issue at 

 numerous places along the beach below high-tide level. There 

 is a wide fringe reef of the sandstone along the beach near the 

 Camocim lighthouse, but at the light, which is 175 yards back 

 from the beach, good water is obtained at approximately sea 

 level in a shallow well in which rock was not encountered. 

 The well, however, is possibly not deep enough to determine 



* A record of the materials encountered in this well is given in Jenkins' 

 paper, Proc. Am. Phil. Soc. No. 211, pp. 28-29, 1904. 



