On Coral Reefs and Islands. 339 
of the thermometrical observations of various voyagers with 
those of the Expedition, I have been enabled to draw this coral 
boundary with a:considerable degree of accuracy ; and it is laid 
down upon the chart of the world accompanying my Report. 
In the Pacific it is observed to exclude the Galapagos,* and reach 
the South American coast north of the equator, instead of at the 
parallel of 28° south, the position in mid-ocean... On the coast 
of Asia it curves from the equator beyond latitude 30°. In the 
Atlantic it forms an abrupt bend far to the north, in the line of 
the Gulf Stream, and includes the Bermudas in latitude 32° N.; 
while on the African coast the northern line curves downward to 
avis Pacific Ocean, . Atlantic Ocean. 
East side of ocean—Northern, Latitude 21° N. Latitude 10° N. 
; outhern, =, 4°N. *'s. 
West side of ocean—Northern. ° 84°N. 84° Ni, 
' 80° S., New Holland, o 
Southern. 29° S.. py by ae 8. 
It follows from the above, that while the coral-reef seas are 
about fifty-six degrees wide in mid-ocean, they are in the Pacific 
Seventeen degrees wide on the west coast of America, and sixty- 
four degrees on the Asiatic side. In the Atlantic, they are about 
fifteen degrees wide on the African coast, and fifty-six degrees 
on the coast of America. If we reckon to the extremity of the’ 
bend in the Gulf Stream, the whole width off the east coast of 
America, north of the equator, will be over forty degrees. It is 
‘Obvious that these facts enable us to explain many seeming 
anomalies in the distribution of coral reefs. 
Within the limits included by the coral-reef boundary line, 
those other causes operate which influence the distribution of 
No less 
the formation of reefs; and instances of this influence are nu- 
merous throughout the Pacific. The existence of narrow reefs, 
or their entire absence, may often be thus accounted for, For 
example, in the Sandwich Group, the island Hawaii, still active 
With volcanic fires, has but few traces of corals about it, while 
* Captain Fitzroy, R.N., found the surface temperature of the sea at the Galapa- 
oad a a 3, 1885, 62° to F. Oct, 28, in Int 0° 30/ 8, and 
. 99° 4’ W., the temperature of the sea 66° F. Oct. 24, lat. 0° 23’ N, 
long. 96° 53’ W., temp. 704°, 713° F. While under the equator, about the middle 
of the Excite, the meget suites Seapets ee ees toe 
88° Besl? A bon) emagn aes ats : hone! gre 
