CHAP. VII. | DEEP-SEA TEMPERATURES. 307 
and northwards of the western entrance of the channel. 
We found that in these two areas, freely communi- 
eating with one another and in immediate proximity, 
two totally different conditions of climate existed at 
all depths below the immediate surface, where they 
differed but slightly. In the Féroe channel, at a 
depth of 500 fathoms, the bottom temperature aver- 
aged — 1°-0 C., while at a like depth in the Atlantic 
the minimum index stood at + 6° C., a difference of 
7 degrees Centigrade, nearly 13 degrees Fahrenheit. 
The conclusion at which we speedily arrived as 
the only feasible explanation of these phenomena 
was that an arctic stream of frigid water crept from 
the north-eastward into the Froe channel lying in 
the deeper part of the trough, owing to its higher 
specific gravity ; while a body of water warmed even 
above the normal temperature of the latitude, and 
therefore coming from some southern source, was 
passing northwards across its western entrance and 
occupying the whole depth of that comparatively 
shallow portion of the Atlantic from the surface to 
the bottom. 
Several important facts of very general applica- 
tion in Physical Geography had been placed beyond 
doubt by these observations. It had been shown 
that in nature, as in the experiments of M. Despretz, 
sea-water does not share in the peculiarities of fresh 
water, which, as has been long known, attains its 
maximum density at 4° C.; but, like most other 
liquids, increases in density to its freezing-point : and 
it had also been shown that, owing to the movement 
of great bodies of water at different temperatures 
in different directions, we may have in close proxi- 
x 2 
