J.D. Dana on a supposed change of Ocean Temperature. 391 
Arr. XLIL—On a change of Ocean Temperature that wou 
attend a change tn the level of the African and South American 
Continents ; by James D, Dana. 
Tue idea of a change of climate consequent upon a change 
in the distribution of land and water on the globe, brought Bs 
ability and precision, by Pro - Hopkins, especially with i Be 
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. 
pon the oceanic isothermal chart issued with the last number 
dered by cold waters; and that while in the Pacific, 80° F. is 
the coldest temperature of the year in mid-ocean, towards South 
merica, even under the equator, the ocean temperature of 74° 
is not found, in the cold season, short of a distance of 2500 miles 
rom the c 
We besa also remarked upon the evidence that a similar south- 
ern or extratropical current affects the temperature of the whole 
Southern Atlantic, me page 320) and makes this literally the 
cold ocean of the 
t is moreover sah ol from the temperature of the waters off 
lantic ; 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 
1300 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 temperature of the waters off this coast. The posi- 
tion of the isocryme of 35°, shows that this same current flows on, 
rising somewhat northward towards Cape of Good Hope; yet the 
African continent lies so far to the north, that it can in fact inter- 
cept but a —_ part of the southern current, which consequently 
to a large extent passes on south of the Cape ; yet this small part 
produces a pn BiH effects pointed out.* 
* We find that at the recent meeting of the British Association, Mr. A. G. Find- 
lay, in the course of a paper on the oceanic currents of the Atlantic and — 
takes the common view that the — tae is the origin 0 clin 
flows up the West African coast, a view shown on page 322 eckn wae 
