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Vestenfor Linien mellem Tromsø og Spidsbergen og
vestenfor samt nordenfor denne Ø styrter derimod Bunden
sig ned til et stort Dyb, der midt imellem Spidsbergen og
Grønland maaler 2650 Favne, en Dybde, der rivaliserer
med selve Atlanterhavets. Fra den nordlige Side af
Bassinet haves ingen Lodninger; kun ved man, at den
vulkanske Ø Jan Mayen styrter sig meget brat ned i Havet.
Heller ikke ved man, hverken hvorledes Bankerne paa
Islands Vestkyst eller Flakket mellem Island og Færøerne
gaa over til Ishavsdybet. Forholdene mellem Færøerne og
Skotland ere derimod nøie undersøgte af “Porcupine”-Expeditionen
i 1869. Her gaar fra Ishavet en smal Rende
paa 600 Favnes Dyb ned i Atlanterhavet. Denne Rende
samt den formodentlig dybe Rende mellem Island og
Grønland synes at være de eneste Communicationsveje i Dybet
mellem Atlanterhavet og vort Ishav. Paa den norske Side
strækker Kundskaben om Havbundens Fonn sig saagodtsom
ikke udenfor de af Fiskerne besøgte og af “Hansteen”-Expeditionerne
oploddede Banker. Kun paa et eneste Sted,
ved Storeggen, have disse Lodninger antruffet en rask
Heldning af Bunden ud mod det store Hav-Bassin. Ellers
ere vi totalt uvidende om, paa hvilken Maade vor Kysts
Banker gaa over i Ishavsdybet, om det sker brat, eller
langsomt, om det sker nær Kysten eller om det først finder
Sted langt ude i Søen. Kundskaben om dette Punkt er
det netop, som vi maa anse det for et Hovedpunkt at
vinde.
Med Hensyn til Temperaturen i det her omtalte Strøg
af Havet er vor Kundskab indskrænket omtrent til de
samme Localiteter, som de hvor Dybdeforholdene ere
undersøgte. Temperaturmaalingerne fra vor Kyst vise, at vore
Banker og vore Fjordes tildels store Dyb dækkes af Vand,
hvis forholdsvis høje Varmegrad viser hen til Atlanterhavet
som dets Udspring. Intetsteds langs Norges Kyst er der
paa Bankerne eller Fjordenes Bund fundet Kuldegrader.
Saadanne ere derimod fundne ikke alene saavel i Overfladen
som i Dybet ude i Havbassinets centrale Del og henimod
dets vestlige Rand, men ogsaa i den dybe Rende mellem
Færøerne og Shetland allerede i 300 Favnes Dyb.
Hvor langt vi maa gaa ud i Havet vestenfor Norge forat
træffe paa iskoldt Vand paa Bunden, derom staa vi aldeles
blottet for Kundskab. Her staa vi atter ved et Hovedpunkt,
thi denne Grændse mellem det varme Atlanterhavsvand og
det iskolde Polarvand maa, efter det hvad der kan sluttes
af lignende Forhold, betegne Grændsen for de i Havet
levende Væseners forskjellige Udbredelse til den ene eller
til den anden Side. End ringere end vor Kundskab om
Dybde- og Varmeforhold er vor Kundskab om Strømforhold,
der spiller en saa stor Rolle i Dyrelivet, om Havvandets
Bestanddele, der er af lige Vigtighed, og om de
jordmagnetiske Forhold, der for Theorien som for Skibsfarten er
af sær Betydning.
West of a line extending between Tromsø and
Spitzbergen, as also west and north of the latter locality, the
bottom sinks to a great depth, reaching between
Spitzbergen and Greenland 2650 fathoms, and accordingly
rivalling that of the Atlantic itself. Along the northern
boundary of the basin no soundings have as yet been taken;
all we know is, that the volcanic island of Jan Mayen
plunges precipitately into the ocean. Nor is it yet known
how or where the banks on the west coast of Iceland and
the flat between Iceland and the Færoe Islands, pass into
the depths of the Arctic Ocean. The section stretching
between the Færoe Islands and Scotland, was, on the other
hand, carefully explored on the “Porcupine” Expedition,
in 1869. In this tract, a narrow channel, 600 fathoms
deep, extends from the Arctic Ocean to the Atlantic. This
channel, and probably too the deep channel between
Iceland and Greenland, would appear to be the only highways
by which the depths of the Atlantic are connected with
those of the Arctic Ocean. Along the Norwegian coast,
what we know of the nature and contour of the bottom is
almost exclusively confined to that of the banks periodically
visited by fishermen, and which of late years have been
investigated on the Coast Survey expeditions with the
“Hansteen.” In but one locality — off the Storeggen bank —
was the bottom found to sink rapidly down to the great
ocean-basin. With this exception, we are totally ignorant
as to how and where the banks lying off the coast of this
country pass into the depths of the Atlantic, whether
gradually or precipitately, whether in close proximity to
the coast or possibly in mid-ocean. Now. the solution of
this problem appears to us of the greatest importance.
As regards the temperature throughout the aforesaid
ocean-tract, it is known only for most of the localities in
which the depth has been measured. The comparatively
high temperature distinguishing the water on our coastal
banks and in our fjords, many of which are of great depth,
points to the Atlantic Ocean as the source whence it is
derived. Nowhere along the coast of Norway, whether on
the banks or at the bottom of the deepest fjords, has 0°
been observed; but in the central part of the ocean-basin,
and at its western margin, the temperature has been found
to be below zero, both at the surface and in the depths;
nay, in the deep channel between the Shetlands and the
Færoe Islands 0° is reached at a depth of 300 fathoms.
At what distance from the western shores of Norway
the glacial bottom-area commences, we are unable to infer
from the data as yet obtained. Here, then, we stand in face
of another highly important question: for the limit at which
the warm water of the Atlantic meets the cold indraught
from the Polar Sea, must, reasoning from analogy, mark
the limit of distribution for the animals inhabiting the
warm and cold areas. But, trifling as is our knowledge
of depth and temperature in that ocean-region, we know
still less concerning the nature of its currents, — a
physical condition which everywhere exerts such great influence
on the character of the marine fauna, — concerning the
chemical constituents of its water, — no less important in
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