204 BULLETIN : MUSEUM OF COMPAKATIYE ZOOLOGY. 



Of the Peruambuco reef he says that bits of lava have beeu thrown 

 upon the reef from which it has been stated that the reef is of igneous 

 origin ; this he says should deceive no one. 



Cazal, Ayres de. Corografia Brazilica. Rio de Janeiro, 1817, II. 169 

 The author says the bay at Cururipe is protected by a reef, but 

 whether coral or stone, lie does not say. The reef in front of Pernam- 

 buco, he says, extends from Bahia to Cape St. Eoque (173) parallel with 

 and a short way from the shore ; that it is at the level of high tide, 

 and six feet above low tide, perpendicular on the inside and sloping 

 outward. 

 Dapper, Dr. O. See Montanus, A. 



Darwin, Charles. On a remarkable bar of sandstone off Pernambuco 

 on the coast of Brazil. The London, Edinburgh, and Dublin Philo- 

 sophical Magazine and Journal of Science. Oct., 1841, XIX., p. 257- 

 261. 



This is the earliest geological description of the Pernambuco stone 

 reef. It contains a cut showing a cross-section of the reef. He says 

 that "it consists of a hard pale-colored sandstone, breaking with a very 

 smooth fracture and formed of siliceous grains cemented by calcareous 

 matter. "Well-rounded quartz pebbles from the size of a bean, rai'ely to 

 that of an apple, are imbedded in it, together with a very few fragments 

 of shells." 



He thinks that its having withstood the action of waves so long is 

 " owing to the protection afforded by the thin coatings of Serpulae and 

 other organic beings." He thinks that it is formed by the agency that 

 made the linear islands on some coasts, such as the Gulf of Mexico. It 

 is suggested that if the nucleus of a sand spit were once consolidated, 

 a small change of level or of currents might cause the loose sand to be 

 washed away, leaving such a structure as the reef, which might be pre- 

 served from complete destruction by protection of animals. 



Darwin, Charles. Journal of researches into the natural history and 

 geology. Voyage of the Beagle. Xew York, 1878, p. 198-199. 

 Mr. Darwin here remarks that he doubts " whether in the whole world 

 any other natural structure has so artificial an appearance." He ex- 

 presses the opinion that the reef was formed by the consolidation 

 (through percolation of calcareous matter) of a long spit or bar of looce 

 sand, and afterwards gradually upheaved. " The oldest pilots know of 

 no tradition of any change in its appearance." This durability he at- 

 tributes to the coatins: of calcareous matter on its seaward face. 



