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20
84. 85 og 87. fjerne sig om mere end 1 Procent fra det
almindelige Resultat, medens man af samtlige Observationer
kan bestemme en enkelt Observations sandsynlige Afvigelse
fra den efter denne Tabel optrukne Curve til + 0.52 °/0,
en Afvigelse saa liden, at en ikke ringe Del af den kan
skrives paa Observationsfeil.
De største Uoverensstemmelser optræde talrigst i et
Dyb fra 300—600 Favne (549—1097 Meter) men tindes
ogsaa enkeltvis i større Dyb.
Fra Bunden hidrører i de større Dyb kun to
Luft-prøver med væsentlig for høi Surstofprocent nemlig No.
68 og 87, optagne fra to Puncter, som mærkeligt nok
begge ligge paa en Linie paralel med og tæt ved
Grændsen mellem den nordover strygende varme Strøm og den
sydover forbi Jan Mayen gaaende Polarstrøm. Bortser
man imidlertid fra disse de væsentligste Uoverensstemmelser,
som bidrage til at give Curven et om end meget svagt
Minimum i .300—400 Favnes (549—732 Meters) Dyb, vil
man i Korthed kunne udtale Regelen for Surstofprocentens
Aftagen med Dybet saaledes: Surstofprocenten er i
Overfladen gjennemsnitlig 35.3 og aftager derpaa først
hurtigt senere langsommere til henimod 32.5 i 300 Favnes
(549 Meters) Dyb, hvorfra den med stigende Dyb holder
sig paa det Nærmeste constant. Det kan bemærkes, at af
de her undersøgte Vandprøver 40 ere øste lige ved
Havbunden. Man vil imidlertid forgjæves bestræbe sig for at
opdage nogen Forskjellighed i Egenskaber mellem disse og
de fra ligestore intermediære Dyb optagne.
Hvor det gjælder at studere Variationerne af den
absolute Luftmængde, maa det synes naturligt som Maal
for denne at benytte den opløste Kvælstof, idet den
observerede Luftmængde paa Grund af det vedvarende
Forbrug af Surstof i de dybere liggende Lag bestandig kan
forudsættes at være mere eller mindre forskjellig fra den
Mængde, som vilde absorberes i Overfladen under directe
Paavirkning af Atmosphæren. Kvælstofmængden kan
derimod paa Grund af denne Gasarts stærkt udprægede
Indifferentisme ligeoverfor andre Legemer uden synderlig Feil
antages uafhængig af locale Tilfældigheder.
Anvendes saaledes Kvælstofmængden som Maal for
den i Søvandet opløste Luft, viser der sig i Fordelingen
ogsaa hér en udpræget Lovmæssighed, naar undtages, at
der i cle af Svendsen paa det første Togt udførte
Observationer overalt er fundet en mindre Kvælstofmængde, end
man efter alle øvrige foreliggende Observationer skulde
vente. Bortser man imidlertid fra disse paa første Togt
udførte 14 Observationer, vil man se, at alle de Øvrige
paa laa Undtagelser nær meget vel stemme overens med
de Tal, man kan beregne efter den ved de ovenciterede
Forsøg bestemte Formel
85, and 87 exhibiting a difference of more than 1 per cent
as compared with the general result, whereas the probable
deviation of a single observation from the curve drawn
according to this Table may be computed at + 0.52 per
cent, a deviation so small as to arise, probably, in no
slight degree from errors of observation.
The greatest discrepancies refer chiefly to a depth of
300—600 fathoms (549—1097 metres); now and again,
however, they were met with in water obtained from greater
depths.
In only two of the samples of air expelled from
bottom-water drawn where the depth was great, did the
percentage of oxygen prove much too high, viz. in Nos. 68
and 87. the samples of water yielding them having been
obtained from two spots which, strange to say, are in a
line running parallel and in close proximity to the
boundary between the warm current flowing north and the cold
Arctic current flowing south past the Island of Jan Mayen.
Now, if we exclude from these differences the chief of those
that contribute towards giving the curve a very slight
but appreciable minimum at a depth of from 300 to 400
fathoms (540—732 metres), the rule according to which
the proportion of oxygen is found to diminish with the
depth may be expressed as follows: — The proportion of
oxygen, which at the surface is 35.3 per cent, begins at
once and continues to diminish, at first rapidly and
afterwards at a slower rate, till it has reached 32.5 per cent,
at the depth of 300 fathoms (549 metres), from whence it
keeps almost constant. I will not omit to observe, that of
the samples of water examined 40 had been drawn from
the bottom; is was, however, impossible to detect any
difference in composition between these and the samples
obtained from equal intermediate depths.
When investigating the variation in "the absolute amount
of air, .it will obviously be advisable to make use of the
nitrogen absorbed, since the quantity of air observed in
the deeper strata may. by reason of the steady
consumption of oxygen, be assumed to differ more or less from
that which would be absorbed at the surface under the
direct influence of the atmosphere, whereas nitrogen, from
the very slight affinity evinced by that gas for other bodies,
may, without involving appreciable error, be regarded as
proof against the accidents of locality.
If, therefore, the amount of nitrogen be adopted as
the standard of measurement for the air absorbed in
sea-water, a marked uniformity will liere, too, be found to
characterise the distribution, as determined by the
observations described, with the exception however of Svendsens,
on the first voyage, by which the amount of nitrogen was
found to be less than all subsequently instituted observations
gava reason to expect. Excluding, then, the 14
observations from the first voyage, all of the others, with but few
exceptions, agree closely with the figures which may be
found by the formula stated above -
iVrr 14.4 — 0.23 t.
N= 14.4 - 0.23 t.
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