256 CORALS AND CORAL LSLANDS. 



observations of various voyages with those of the Expedition, the 

 author has been enabled to draw these boundary lines with a 

 considerable degree of accuracy, and they are laid down upon 

 the chartof the world published in his Report (Wilkes's Explor- 

 ing Expedition) on Geology, and, with other isocrymal lines, 

 on a full isocrymal chart of the globe, in his Report on Crus- 

 tacea, from which it was reproduced in volume xv. (1853) of 

 the second series of the Ame?'ican Journal of Science, which is 

 now again issued at the close of this volume. 



In the Pacific Ocean, this coral boundary, or isocryme of 

 68°, excludes the Galapagos from the coral sea-s, making a 

 bend around them, and passing for a short distance even north 

 of the equator, instead of near the parallel of 28° south, its 

 position in mid-ocean. Captain Fitzroy, R.N., found the 

 surface temperature of the sea at the Galapagos, from Sept. 

 16 to Oct. 18, 1835, 62° to ,70° F. Oct. 23, in lat. 0° 30' S., 

 and long. 99° 4 W., the temperature of the sea was 66° F. ; 

 Oct. 24, lat. 0° 23' N., long. 96° ^53' W., temp, yoi", 714° F. 

 While, under the equator, about the middle of the Pacific, the 

 range of surface temperature of the sea through the year is 

 81° to 88° F. 



On the side of Asia the boundary line bends far southward, 

 and reaches the coast of Cochin China within 15° of the 

 equator, although 30 ° from the equator a little to the eastward. 

 On the west side of the Atlantic, the northern line starts at 

 Cape Florida, in latitude 15 ° N., stretches abruptly northward, 

 and bends around the Bermudas in latitude 33 ° N. On the 

 African coast opposite, the northern line curves dow^nward to 

 the latitude of the Cape Verds, and the southern upward 

 nearly to the equator. The following table gives the positions 

 of the coral boundary lines where they meet the coasts of the 

 continents : — 



Pacific Ocean. Atlantic Ocean. 



East side of ocean — Northern, Lat. 21" N Lat. 10° N. 



Southern. 4° S 5° S. 



West side of ocean— Northern. 15° N. 26° N. 



Somhern. S 3°° S., N Holland. j ^^„ g, 

 ( 29° S., Africa ) 



