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74
sernes Vedkommende af saadan Størrelse, at de i
Sammenligning med de smaa Differentser, som det lier gjælder at
paavise, lettelig paa sine Steder kunne gjøre sig gjældende
og frembringe Uoverensstemmelser, livor de i Tilfælde af
absolut nøiagtige Observationer ikke vilde lindes.
Hvilken Vægt man nu end vil tillægge disse faa
Forskjelligheder mellem de to Karter, saa meget er dog sikkert,
at de kun optræde som Undtagelser, medens den langt
stærkere fremtrædende Regel er Overensstemmelser af saadan
Art. at de ikke uden videre kunne tilskrives Tilfældigheder.
Der existerer uimodsigeligt en paa mange Puncter næsten
til Proportionalitet grændsende lovmæssig Forbindelse
mellem Saltgehalten og Kvælstofmængderne, som muligens ikke
turde lade sig forklare paa anden Maade end netop
gjennem den før omtalte Hypothese, som saaledes maa ansees
for at indeholde ialfald en stor Del Sandhed, idet den
samtidig bestyrkes, af to af hinanden fuldstændig uafhængige,
uensartede Observationsrækker, der i alt Væsentligt give
det samme Resultat.
Den, som det synes, største Vanskelighed ved denne
Hypothese bestaar i at forklare, hvorledes det i de store
Dyb flydende atlantiske Vand skulde have antaget en saa
lav Temperatur, som clet ifølge Observationerne viser sig
at besidde. Dette turde -dog maaske ikke synes saa
urimeligt, uaar man betænker, at den varme, søndenfra kommende
Atlanterhavsstrøm ved at flyde henover det underliggende
meget kokle Vand paa de nærmest til dette grændsende
Lag maa blive udsat for en meget stærk Afkjøling
nedenfra, og" at det først gjennem en saadan Afkjøling til
omkring 0° opnaar den høie specifiske Vægt, der er den
nød-.vendige Betingelse for, at det skal kimne synke tilbunds.
Det atlantiske Vand har altsaa, allerede førend det
begynder at synke, antaget en meget lav Temperatur og vil
desforuden uncler selve Synkningen, idet det da kanske i
et meget langt Tidsrum befinder sig paa alle Sider omgivet
af polart Vand, end yderligere blive Gjenstand for
Afkjøling, førend det naar Bunden. Det fremgaar forøvrigt
ogsaa af de endnu ikke offentliggjorte
Temperaturobservationer, som jeg desuagtet ved Velvillie af Professor Mohn
har faaet Anledning til at gjøre mig bekjendt med, at
Temperaturen i de store Dyb paa de med rød Farve
betegnede Partier er noget høiere end der, hvor Kartet er
farvet blaat, saaledes at i Virkeligheden ogsaa
Temperaturforholdene tale for den opstillede Hypothese.
Det vilde dog være paa urette Sted paa dette
Stadium at forsøge udredet alle Vanskeligheder, saalænge de
paa Expeditionen udførte talrige Temperaturbestemmelser
endnu ikke ere forelagte Offentligheden, da man alene ved
at tage tilbørligt Hensyn til det hele foreliggende Materiale
af Observationer vil kunne vente at faa det bedst mulige
Indblik i de mere indviklede Spørgsmaal 0111
Strømforholdene. Det er dog meget sandsynligt, at man senerehen
ved at combinere alle Data vil kunne kaste Lys over
meget, som nu maa synes dunkelt.
Uheldigvis var det ved Expeditionens Udreise ikke
muligt at forudse, at de chemiske. Observationer skulde
kunne føre til Slutninger af saadan Art som de her paa-
of the computations, they might easily affect the result,
and give rise to discrepancies which, with perfectly accurate
observations, there would be no fear of.
Whatever weight may be attached to these differences,
they must unquestionably be regarded as exceptional; the
rule is agreement, and of a character precluding the
possibility of ascribing it to chance. Many of the observations
prove incontestibly the existence of a definite, well nigh
proportional connexion between the amount of salt and
that of nitrogen,"a connexion difficult, perhaps, to explain
without having recourse to the aforesaid hypothesis, which
cannot but come near the truth, confirmed as it is by
two widely different series of observations, leading, each
independently of the other, in all essential points, to the
same result.
The greatest apparent difficulty involved in this
hypothesis consists in explaining the low temperature of the
Atlantic water in the deeper strata. We must, however,
bear in mind that the warm Atlantic current, in flowing
over the cold water of the lower strata, is necessarily
made to part with a very considerable amount of heat;
and that the high specific gravity, without which it could
not sink to the bottom, involves a temperature of about
0°. Hence, the Atlantic water will have acquired a very
low temperature before beginning to sink, and moreover,
being surrounded during its downward passage, possibly
for a considerable period, by Polar water, give off a further
amount of heat ere it reaches the bottom. For the rest,
it appears from the independent series of temperature
observations, not yet in print, with which Professor Mohn
has kindly made me acquainted, that the temperature at
great depths in the sections coloured reel in the Plate,
is somewhat higher than in those coloured blue; and hence
the hypothesis adopted here derives additional support from
the variation in temperature.
Meanwhile, it would be premature to attempt
disposing of all difficulties, till the numerous temperature
determinations performed on the Expedition shall have
been made public, since to elucidate fully the more
intricate questions connected with ocean currents, the whole
stock of materials must be dealt with. We may however
venture to hope, that, at a later stage of this interesting
inquiry, a geheral combination of data will throw light
upon much that is at present involved in obscurity.
Unfortunately, it was not possible to foresee on the
departure of the Expedition, that such inferences as those
here pointed out would be drawn from the chemical ob
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