The herald and mail. [volume] (Columbia, Tenn.) 1873-188?, 1875-10-22

! II we admit that, alike IN the NOrJn anu
in the South Atlantic, this upper stratum
is being drawn pole-wards by cis a
| frontre generated by the continual de-
scent of the water that comes under the
influence of polar cold, we see how the
excess of thickness it possesses In the
northern hemisphere enables 1t to lmpart
/ to the atmosphere above 1t correspond
| ing amount of warmth. For, as every
surfce-flm that has given up its heat to
the air above it, sinking until it meets
with water as cold as itself, Is replaced
| by the uprising eff warmer water from
| beneath, so, the further down the excess
of warmth extends, the longer will it be
/ before the temperature of the surface Is
reduced to that of the air abOve-just as
| the surface of a deep lake remains I'M
CONCEALED by frost which forms thick
layer of ice on a shallow pond or mere.
| 1t was urged several years ago, by the
late Mr. Findley. that supposing the Gulf
| Stream proper to have a continuous on
ward movement to the western shores OF
! Great Britain, the thinness OF It's eXpan-
! sion, and the slowness of its rate, where
| If is last recognizable as a current, would
| subject it to the loss of all its surplus
| heat. long before it reaches our coast and
this argument is strongly confirmed by
the fact, that the upper stratum of the
Mediterranean, though heated by the
summer sun to quite as high a tempera-
ture as that of the Gulf Stream in the
mid-Atlantic, loses its excess of warmth
with the seasonal reduction in the tenn
perature of the atmosphere above it;
whilst, as soon as its surface has been
cooled down to the constant temperature
90 ho1
further reduction, whatever may be the
temporary depression of the atmospheric
temperature. And in this manner we
find that the moderate, but permanent,
elevation of the uniformly heated mass
of Mediterranean water, has far more
potent influence in ameliorating the eli
mate of its northern shores, than the
transient experimenting of its surface
layer.
But it does not hence follow that Mr..
Findley was right in attributing the
ameliOration of the climate of north
western Europe, as DR.. Hayes has since
done, solely to the heat transported by
the south-westerly winds; for the very
careful and systematic observations which
have now been carried on for some years
under the able direction of Professor
temperatures of the air and the sea along
the coast of Norway, have shown that
the latter has an average excess of warmth
during the four winter months, amount
ing to 14'5o Fair. This excess he very
naturally attributed, in the first instance,
to the influence of the Gulf Stream; but
he has latterly expressed his concurrence
in my own view, that the pOleward trans
~ g Il of
a far larger and deeper movement, for
which the general oceanic circulation
alone can adequately account.
This view derives further confirmation
from the extension of the Challenger
inquiries into the Antarctic Ocean, by a
southwark DETECTION from her course be-
tween the Cape of Good Hope and
Sydney. For it becomes plain, from an
examination of the temperature-sectiOns
taken in this part of her voyage, that the
comparative GOODNESS of the southern
oceans is essentially due, not so much to
the want of a superheated surtace-layer,
As to the rapid reduction in the tempera-
ture of the whole comparatively thin
upper warm stratum under the influence |
of atmospheric cold: the isOtherm of |
40o, which lies below four hundred faith |
oms in lat. 80 S., rising to one hundred |
and fifty fathOms in lat. 460 s, and |
actually coming to the surface near |
Kerguelen's Land (lat. 500 5. }, while it |
lies below eight hundred fathOms in the |
corresponding northern parallel. Thusit |
comes to pass that the summer climate of
Kerguelen's Land, as Captain Mares re-
marks, is comparable to the winter eli
mate of che British Isles; and that |
glaciers there descend from the noun
tains almost to the waters edge, remind
ing us of the ice-sheet which covered the
surface of North Britain during the
glacial epoch.
The Challenger" approached the
antarctic ice-barrier in the height of the
southern summer, when the influence of
solar radiation was exerted in melting the
ice-bergs and the edge of the tield-ice,
and thus in lowering rather than raising
the temperature of the surface-water, |
which was found to be pretty constantly |
that of melting ice as far down as the
thickness of the ice extended. This was
exactly what had been anticipated; for
the water thus chilled does not descend, |
but remains floating at the surface, i'll
consequence of the lower proportion of
salt which it contains; and yet it does not |
rise in temperature, because any further
accession of heat it may receive from the
sun is expended in melting more ice.
But underneath this stratum of half-salt |
glacial water, there was found Il stratum
of ordinary sea-water having tempeTa
ture between 80 and 80 and this was
obviously continuous with the proper
surface stratum at such a distance from
the icG-barrier as to be out of the reach |
of melting ice; whilst there was every
reason to believe that the whole subia- |
cent mass down to the bottom had a tenn
perature of 80 or less. Now, it is
obvious that as this warmer stratum
could not have derived its heat from local
solar radiation, it must have brought it
from elsewhere; and as there is no Gulf
Stream in the southern ocean, there
seems no other agency to account for its
presence, than the polar indraught which
has been so frequently referred to.
HThus the observations upon ocean tenn
perature hitherto collected by the " ChaI-
lenger," in the North, Equatorial, and
South Atlantic, in the Antarctic, and in
Eastern Archipelago, not only prove con-
formable in very particular to the doc
trine they were designed to test, but do
not seem capable of any other expla-
nation.
The OBSERVATION-DISCLOSURES recently
made in the North Pacific by the United
States ship "Tuscarora, which was
commissioned to carry line of soundings
for a telegraph cable this vast ocean-basin
from the coast of California to Japan,
making the Sandwich Islands halfway
station, enable us to test this doctrine
by case which presents a marked dis
of conditions. For, although
the North Pacific has communication
with the arctic basin through Behring's
Strait, yet this is two shallow, as well as
narrow, to admit of any outflow of
glacial water from the latter into the
former. Now, as the average depth of
the North Pacific is considerably greater
than that of the North Atlantic, and as
there is reason to believe that this excess
extends to the South Pacific also, we
should expect, on the principle already |
stated (P. y, that the influence of an
tarctic cold will be strongly eXerted
throughout the whole of it; and this is
fully borne out by the "Tuscarora OBJ
;ervations. For the bottOm-temperature,
1t depths exceeding two thousand faith