310 Association of American Geologists and Naturalists. 
Arr. X.—Abstract of the Proceedings of the Fourth Session of 
the Association of American Geologists and Naturalists. 
(Concluded from page 165.) 
Saturday, April 29, 1843.—After the reading of the minutes, 
Mr. Dana read a paper on the distribution of corals, alluding to a for- 
mer statement of his, (p. 145) that the reef-forming corals are limited in 
their distribution in our present seas by the temperature of 66° Fah., and 
also to the fact of the absence of corals from the Gallapagos under the 
equator, and their presence at the Bermudas, added farther, that owing 
to these currents the coral zone limited by this temperature was singu- 
larly contracted on the western shores of the continents by the extra- 
tropical currents, and expanded on the eastern by the intratropical cur- 
rents. On the western shores of America it was reduced to 16° of 
latitude in width, and in those of Africa to at least 12°, while in the 
mid ocean the zone is fully 56° wide, and on the eastern coast of Asia 
and New Holland 64°. These facts with regard to the influence of 
oceanic currents, may explain many anomalies in the distribution of 
fossils. Mr. D. denied the truth of Mr. Darwin’s principle, that islands 
with barrier reefs are subsiding, and those with fringing reefs rising, 
and stated that he was not satisfied by his observations, that any eleva- 
tions or subsidences were now in gradual progress in the Pacific or on 
the South American coast. His observations fully confirmed Mr. Dar- 
win’s theory, that atolls or coral islands were once barrier reefs around 
high islands, which high islands have disappeared by subsidence. From 
the distribution of these islands, he drew conclusions different from those 
of Mr. Darwin, with regard to the areas of subsidence. Ifa line were 
drawn in an E. 8. E. direction from New Ireland by the Navigator and 
Society Islands, the islands to the north, with two or three exceptions, 
would be found to be low and coral, and those to the south, high and 
basaltic.* These coral islands diminish in number and size as we re- 
cede to the north from this line, and over a large area between the 
Sandwich Islands and the equator there is an open ocean without is- 
lands. As we go south from the same line, the extent of the reefs 
around the high islands diminishes. From these facts he concluded that 
the subsidence in progress during the formation of these islands was 
greater under the equator where the coral islands were few and small, 
than farther south, where they are numerous and large : that still greater 
subsidence took place over the open seas where the currents were too 
* See the map accompanying Mr. Dana’s article, published in the present vol- 
ume of this Journal, page 131. 
