312 Association of American Geologists and Naturalists. 
of North and South America.* The effect of these cold currents was 
such that the temperature of the sea at the Gallapagos Islands, under 
the equator, was from ten to twenty degrees below that of the Gulf of 
Mexico, and the waters of the Gulf Stream on the coast of the United 
States. Moreover, the observations had shown a great difference in 
the temperature as taken on opposite sides of these islands. This dif- 
ference he had ascribed to the low temperature of the inflowing current 
from the southern hemisphere, which from the observations obtained 
he had supposed to sweep near these islands. Analogous effects had 
also been noticed on the western coast of the African continent; and 
the obvious bearing of the observations which he had collected from 
other parts of the Pacific was to establish the existence and approximate 
outlines of a general system of currents in that vast sea, and which, 
as in other oceans, controls and modifies the temperature of its waters, 
most remarkably, even on the same parallels of latitude. 
He had mapped out the results of his former inquiries on this pre- 
vailing system of both winds and currents on blank charts furnished 
by Mr. Dana, which were intended for the use, as well as correction, of 
the observers of the Expedition. These maps he regretted to say had 
been lost before the end of the cruise, in the wreck of the Peacock. 
He was now pleased to find, however, that the main results as to ocean 
temperature and currents, which had cost him no inconsiderable labor 
at earlier periods, no longer rested on scattered observations made by 
different navigators; but that Mr. Dana, among other highly valuable 
labors, had carefully examined and brought to bear on the case the un- 
deniable evidence of innumerable register thermometers afforded in the 
living corals, which serve to mark with greater certainty and precision 
the extent and boundaries of the warmed waters of the Pacific Ocean. 
Mr. John L. Hayes differed from Mr. Dana on the question of 
general elevation and subsidence in the areas of coral islands; 
his belief was, that according to the views of the great Prussian 
geologist Von Buch, the districts of elevation were limited and 
not contemporaneous. 
Prof. Rogers enquired of Mr. Dana what was the maximum 
rate of subsidence consistent with the growth of corals. 
Mr. Dana replied that there were no definite facts bearing on 
the subject, but that it must of necessity be very gradual. 
Prof. Rogers remarked that if accurate measurements could 
be made for a sufficient period of time on existing reefs, of the 
depth of the water from fixed points, evidence might be accumu- 
* See Mr. Redfield’s paper, at page 293 of this volume. 
