734 R KANSAS CITY REVIEW OF SCIENCE. 
GEOLOGICAL CLIMATES. 
4 ADDISON GARDENS, 
KENSINGTON, 11th February, 1881. 
EpiTor Revi—Ew:—I venture to send you a number of JVature, with a let- 
ter of mine, which I have thought it necessary to write after the perusal of a con- 
troversy that has been carried on for some weeks past, between two distinguished 
men, namely, Mr. Wallace, ance of the Malay Archipelago, and Island Life, etc., 
_and the Rev’d Samuel Haughton, Professor of Geology in the University of Dublint 
on ‘‘Geological Climates,” the former maintaining that were there certain de- 
pressions, or rather submergences of portions of land, tropical currents would flow 
Northward through the openings, thaw all the Polar ice, and make the Arctic 
climate almost if not wholly temperate. 
Prof. Haughton takes quite an opposite view, and thinks the ice-cap at or 
near the Pole may be hundreds of feet thick, and that the Arctic current flowing 
South would interfere materially with the heating influence of the tropical stream. 
So much is required to explain the meaning of my letter, which, from fearing 
it would occupy too much space, I did not make so explanatory asI could have 
wished. Yours Truly, JouN Rae. 
‘¢T have read with much interest and attention the letters that have appeared 
in recent numbers of /Vature on the subject of ‘‘geological climates,” and although 
it must appear presumptuous on my part to doso, I shall endeavor to show that 
each of the distinguished writers of these letters may be somewhat in error on at 
least one point, which—if I am right— must materially affect the correctness of 
the conclusions they have come to. 
I think that Mr. Wallace, whilst very justly giving the Gulf Stream and other 
currents, which mgh¢ exist were certain lands submerged, credit for great influ- 
ence in ameliorating the rigor of climate, does not take into sufficient considera- 
tion the fact that the waters of the Gulf Stream, although warmer, are, in conse- 
quence of holding much more salt in solution, heavier than the colder and less 
saline Arctic current. 
Some experiments show, as s clearly as anything done on a en small scale 
can, that two waters brought as nearly as possible to the conditions of the Gulf 
Stream and the Arctic current do not mingle when simultaneously poured into a 
long narrow glass trough; the Arctic water invariably taking its place on the 
surface. 
Supposing then that these two currents meet somewhere about latitude 80° 
or 81° N., the Arctic water flowing south—if my experiments are of any value— 
will retain its position on the surface and the warm current pass underneath, and 
thus lose all its heat and influence on the air over a Polar area about 1000 geo- 
graphical miles or more in diameter. 
We can have no stronger example of this effect of difference of density of 
ocean water than is shown by the two currents zz and ou¢ of the Mediterranean Sea. 
