316 CORALS AND CORAL ISLANDS. 



the west shores of the Gulf of Mexico, as well as the northern, 

 like West Florida, are mostly low, and without reefs ; they 

 are within the influence of the Mississippi and other large 

 rivers. Some species of reef corals however occur in the 

 vicinity of Aspinwall (p. 113). The Bermudas are of coral 

 origin, and the most northern point of growing reefs. 



South of the equator, on the east coast of South America, 

 there are reefs at intervals, from the vicinity of Cape St. 

 Roque to the Abrolhos shoals in latitude 18°, as described by 

 Prof. C. F. Hartt, while reef corals extend south to Cape Frio. 

 Descriptions of part of the Abrolhos reefs are given on page 

 140. North of the Abrolhos reefs, there are others of coral 

 stretching on to Point Carumba ; again, off the Bay of Porto 

 Seguro, and across the Bay of Santa Cruz ; in the vicinity of 

 Camamu, around Quieppe Island ; along the shores of Ita- 

 parica Island ; and at Bahia and Periperi ; then, after an in- 

 terruption, off Maceio, in the vicinity of Pernambuco. More- 

 over the Roccas, a cluster of reefs in the latitude of Fernando 

 do Noronha, are, as Hartt observes, probably of coral. 



It is thus seen that the earth is belted by a coral zone, 

 corresponding nearly to the tropics in extent, and that the 

 oceans throughout it abound in reefs, wherever congenial sites 

 are afforded for their growth. It has also been shown that 

 the currents of extra-tropical seas, which flow westward, and 

 are interrupted and trended toward the equator by the con- 

 tinents, contract the coral seas in width, narrowing them to a 

 few degrees on the western coasts of the continents ; while 

 the tropical currents flowing eastward, diverge from the equa- 

 tor, and cause the belt to widen near the eastern shores. The 

 polar currents flow also by the eastern coasts, preventing the 

 warmer waters from increasing the width of the coral zone as 



