266 APPENDIX. 



be thought to be of coral formation, but when beheld at low 

 water might be mistaken for an artificial breakwater, erected 

 by cyclopean workmen. At low tide it shows itself as a 

 smooth level- topped ridge, from 30 to 60 yards in width, 

 with even sides, and extending in a perfectly straight line, for 

 several miles parallel to the shore. OfF the town it includes a 

 shallow lagoon or channel about half a mile in width, which 

 further south decreases to scarcely more than a hundred 

 yards. Close within the northern point, ships lie moored to 

 old guns let into the reef. Here, on the inner side, at low 

 water spring-tides, a section of about seven feet in height is 

 exhibited. This consists of hard pale-coloured sandstone 

 breaking with a smooth fracture, and formed of siliceous 

 grains, cemented by calcareous matter. Well-rounded quartz 

 pebbles, from the size of a bean, rarely to that of an apple, are 

 embedded in it, together with a very few fragments of shells. 

 Traces of stratification are obscure, but in one spot there was 

 an included layer of stalactitic limestone, an eighth of an inch 

 in thickness. In another place some false strata, dipping 

 landwards at an angle of 45°, were capped by a horizontal mass. 

 On each side of the ridge quadrangular fragments have sub- 

 sided ; and the whole mass is in some places fissured, appa- 

 rently from the washing out of some soft underlying bed. One 

 day, at low water, I walked a full mile along this singular, 

 smooth, and narrow causeway, with water on both sides of me, 

 and could see that for nearly a mile further south its form re- 

 mained unaltered. In Baron Roussin's beautiful chart of 

 Pernambuco (Le Pilote du Bresil) it is represented as stretch- 

 ing on, in an absolutely straight line, for several leagues ; how 

 far its composition remains the same, I know not ; but from 

 the accounts I received from intelligent native pilots, it seems 

 to be replaced on some parts of the coast by true coral-reefs. 



The upper surface, though it must on a large scale be 

 called smooth, yet presents, from unequal disintegration, nu- 

 merous small irregularities. The larger imbedded pebbles 

 fctand out supported on short pedestals of sandstone. There 



