92 James D. Dana on a 
On a Change of Ocean Temperature that would attend a 
Change in the level of the African and South American 
Continents. By JAMES D. DANA. 
The idea of a change of climate consequent upon a change 
in the distribution of land and water on the globe, brought 
forward by Sir Charles Lyell, has recently been discussed 
with much ability and precision, by Prof. Hopkins, especially 
with reference to the Northern Atlantic. As there is profit 
' in this consideration of possibilities, whether we can prove 
the actual occurrence of the supposed events or not, we 
briefly remark in this place upon another geological change 
that would affect the temperatures of both the Pacific and 
Atlantic Oceans. 
Upon the oceanic isothermal chart issued with the last 
number of this Journal, and discussed in that and this num- 
ber, it is observed that the whole western coast of South 
America is bordered by cold waters; and that while in the 
Pacific, 80° F. is the coldest temperature of the year in mid- 
ocean, towards South America, even under the equator, the 
ocean temperature of 74° is not found, in the cold season, 
short of a distance of 2500 miles from the coast. 
We have also remarked upon the evidence that a similar 
southern or extratropical current affects the temperature of 
the whole southern Atlantic, and makes this literally the 
cold ocean of the globe. 
It is moreover evident from the temperature of the waters 
off western South America,.that the extratropical or antarctic 
current has a vastly wider influence here than in the southern 
Atlantic ; the positions of the lines of 68° and 74° in the two 
regions make this sufficiently apparent. It is also obvious, 
that the South American Continent, by extending so far 
south,—22 degrees, or 1800 miles, beyond the south point of 
Africa,—should necessarily intercept to a large extent the 
antarctic current, and thus occasion, in connection with other 
causes, the northern flow that influences so widely the tem- 
perature of the waters off this coast. The position of the 
isocryme of 35°, shews that this same current flows on, rising 
somewhat northward towards Cape of Good Hope; yet the 
