204 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
Of the Pernambuco reef he says that bits of lava have been 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, he does not say. The reef in front of Pernam- 
buco, he says, extends from Bahia to Cape St. Roque (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. О. бее 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, rarely 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. New 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 loose 
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 coating of calcareous matter on its seaward face, 
