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de observerede store Afvigelser, saaledes tilskreves stærke
Bevægelser af Havoverfladen* enten ved Storme eller paa
anden Maade den Evne’at forøge Surstofmængden og
forringe Kulsyremængden, ligesom rigt Dyreliv ogsaa:
tilskreves en meget stor Indflydelse paa Sammensætningen af den
i Søvandet opløste Luft.
I 1871 udgik atter igjen denne Gang fra Tyskland
en Expedition til Undersøgelse af Østersøen, hvormed som
Chemiker fulgte Dr. O. Jacobsen. Med Resultaterne af
de fra de tidligere Expeditioner hidrørende Gasbestemmelser
for Øie besluttede han sig hverken for den ene eller den
anden af de ved Bonite eller Pörcupineexpeditionen anvendte
Fremgangsmaader men slog ind paa en Middelvei, den eneste,
som i dette Tilfælde kunde føre til paalidelige Resultater.
Han delte Undersøgelserne i to Dele og udførte den
uopsættelige Del af dem nemlig Gasarternes Udkogning
strax, medens han. indseende Umuligheden af at udføre
tilfredsstillende Gasanalyser ombord paa et Fartøi i aaben
So. opsatte deres nærmere Undersøgelse til Hjemkomsten.
Desværre gav Mangelen af en til Optagelse af
Dybvands-prover egnet paalidelig Yandheüter Anledning til, at det
lste Aars Udbytte ;rf denne Expedition for Gasanalysernes
Vedkommende reducerede sig til blot og bart Indsamling af
den Erfaring, som senere skulde komme til Anvendelse ved
det Aaret efter foretagne Togt’ i Nordsøen. Manglerne
ved den paa Porcupineexpeditionen benyttede Vandhenter
havde nemlig bevæget Jacobsen til ogsaa til Øsning af de
for Gasanalyser bestemte Vandprøver at benytte en
Vand-henter, eier nedsænkedes fyldt med Luft. Naar nu
Apparatet ’i Dybet aabnedes, absorberedes under det der
herskende store Tryk momentant en Del af* den nedbragte
atmosphæriske Luft, hvorved de paa disse Vandprøver
udførte Gasanalyser bleve saa upaalidelige, at der ikke
engang værdigedes dem en Offentliggjørelse.
De paa Østersøtogtet i 1871 indhøstede Erfaringer,
muliggjorde det imidlertid for Jacobsen ved en omhyggelig
Forberedelse til den i 1872 foretagne Expedition i
Nordsøen at overvinde eller omgaa de Vanskeligheder, som havde
bevirket Manglerne ved de paa Porcupineexpeditionen
foretagne Undersøgelser, og det lykkedes ham denne Gang som
Resultat af sine Arbeider at offentliggjøre en Afhandling,1
som giver en Række af vore Tiders Fordringer strengt
tilfredsstillende Oplysninger om Luften i Søvandet. Til
Optagelse af de til Gasanalyser bestemte Vandprøver fra
Dybet tjente paa Nordsøtogtet et af Dr. H.A.Meyer angivet
Apparat2 bestaaende af en tung Metalcylinder, som ved
Udlosning i det bestemte Dyb faldt ned over to vel islebne
koniske Ventiler, og derved afspærrede det mellem disse
"1 Ann. Chem. Pharm. 1 •>" — 1; Jahresbericht (ler Commission zur
wissenschaftlichen Untersuchung der deutschen Meere in Kiel, 1 sT-2
—7.5 — 43.
■ Jahresbericht der Commission zur wissenschaftlichen
Untersuchung der deutschen Meere in Kiel 1872—73- — 5.
pheric pressure is less. But they had recourse to other
means whereby to explain the great differences observed,
ascribing to the state of violent agitation into which the
surface of the ocean is thrown by heavy storms, or to some
other adequate cause, the ability of increasing the proportion
of oxygen and diminishing that of carbonic acid; an
abundance of animal life, too. was believed to exert very great
influence on the composition of the air absorbed in sea-water.
In 1871. an Expedition was despatched from (rermany
for the investigation of the Baltic. Dr. O. Jacobsen
accompanying it as chemist. Warned by ’ the unsatisfactory
results of former gas-analyses, he resolved to adopt neither
of the methods resorted to on the ’Bonite’ and •Porcupine"
Expeditions, but rather to take a middle course, which
indeed held out the only prospect of success.
Accordingly, he divided his observations. Experiments
admitting of no delay, such as boiling off the gas, were
performed’ at once, whereas all analyses of gas, impossible
as it is found to operate satisfactorily on board a vessel
in the open sea, were deferred till his return home.
Unfortunately. the -want of a trustworthy apparatus for
collecting samples of water from great depths, confined the
results obtained on the first voyage of the Expedition,
as regards analyses of gas, to the mere acquisition of
experience, which, however, there was ample
opportunity of applying on the cruise undertaken the following
year in the North Sea. The defective construction of the
instrument employed for collecting water on the
-Porcupine’ Expedition had induced Jacobsen to make use of an
apparatus which, even when drawing water for
gas-anal-yses, was sunk full of* air. Now, on opening this
apparatus at the required depth, some portion of the air it
contains, will, by reason of the great pressure, be
momentarily absorbed; and hence all analyses of gas with such
samples of water proved to that extent defective as to be
not even deemed worthy of publication.
Meanwhile, taking advantage of the experience
acquired in 1871 on the cruise in the Baltic, Dr. Jacobsen
succeeded, after careful preparation to meet the
requirements of the Expedition undertaken in 1872 to the North
Sea, in surmounting or evading the difficulties experienced
on the ’Porcupine’Expedition, and was enabled, as the result
of bis labours, to publish a treatise1 on the air present in
sea-water recording a series of eminently satisfactory .results.
For collecting samples of water wherewith to undertake
analyses of gas in water from the bottom, or from great depths,
an apparatus, described by Dr. H. A. Meyer, was made use
of on the cruise in the North Sea.2 It consists of a heavy
metal cylinder, which, at the required depth, will drop down
on two accurately fitted conical valves, cutting off all coni-
1 Ann. Chem. Pharm. 1 <i7, p. 1: Jahresbericht der Commission zur
wissenschaftlichen Untersuchung der deutschen Meere in Kiel, 1872
—73, p. ,43.
2 Jahresbericht der Commission zur wissenschaftlichen
Untersuchung der deutschen M’eere in Kiel, 1872—73, p. 5.
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