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Siile
Ganske anderledes stiller Forholdet sig. naar
Temperaturen stiger raslet med Dybet. En vastrukken
Trækasse kan da komme til at lade Thermometret registrere
ganske fejlagtige Temperaturer. Et slaaende Exempel
herpaa havde vi paa Station No. 37b. I 170 Favnes Dyb
gav Kviksølvpiezometrct en Temperatur af 2".4<>. Ved
Bunden, i 204 Favnes Dyb, altsaa kun 34 Favne dybere,
gav Kviksolvpiezometret — 0°.51 og Miller-Casella No. i
— ()°.33. begge reducerede for Skalafejl og for Tryk.
Ven-dethermometret Negretti & Zambra Xo. Si) registrerede
Ö°.49. altsaa næsten en hel Grad for højt. Lignende
Forhold vise Stationerne No. 327, 328 og 338. Allerede
i de første Dage af vor Kejse i Øst-havet blev jeg
opmerk-soni paa disse Uregelmæssigheder, og lod derfor altid et
Indextherinometer følge med et Vendethermometer ved
Lodskuddene. Eftersom Trækasserne ved gjentagen Brug bleve
vastrukne, lot! jeg Tømmermanden gjöre nve Kasser, der
benyttedes til de mindre Dybder, saalænge de. efter
anstillet Forsøg i Havvand, bevarede sin Flvdeevne. De
vastrukne Kasser brugtes kun paa større Dyb. Det er ikke
muligt ved Maling eller Fernissering at beskytte Tra>kasserne
saaledes, at de hindres fra at tabe sin Flvdeevne. Heller
ikke er det muligt at gjengive vastrukne Kasser denne ved at
tørre dem og give dem noget Overdrag. Paabundne
Korkstykker kunne hjelpe, men kun for en Tid. Sterke
tilsmeltede Glasrør, indsatte i Kassen, kunde raade Bod paa
disse Ulemper. Nu for Tiden vil man dog foretrække de
senere i Brug komne Vendemekanismer, ved hvilke
Vendingen besørges under Begyndelsen af Ophalingen af en
Skruepropeller, og det vendte Thermometer ikke senere faar
Anledning til at vende sig om igjen. Dette sidste er af
Vigtighed ved Teniperaturnekker, naar man bar liere
Thermometer paa Lødlinen i forskjellige Dybder, og der er
nogen Søgang, ruder saadanne Omstændigheder kan man,
naar man bruger Trækasser, frygte for, at et
Vendethermometer, der allerede har registreret sin Temperatur, vender
sig om igjen paa et højere Trin. idet Fartøjet sænker sig
i Søen.
For at linde den Tid. de forskjelligartede
Dybvands-therinometre behove for at antage det omgivende Vands
Temperatur, gjorde jeg en Bække Forsøg. Thermometret
stilledes i Vand eller en Blanding af Sne og Vand. efter
først at være bleven bragt paa en højere Temperatur. Et
Normaltherinometer angav Vandets Temperatur. Begge
Thermometre stode rolige i Vandet, og dette rørtes ikke
om. Til visse Mellemrum afla’stes
Dybvandsthermome-tret og samtidig dermed af en Assistent Tiden efter et
Sekund ur; umiddelbart oveupaa afladtes
Normalthermome-tret. For hver Aflæsning beregnedes Forskjellen mellem
begge Theriuometres Udvisende. Hermed fortsattes, indtil
at denne Forskjel var bleven constant. Med Argument:
Atla’ste Tidsminuter og Sekunder og Ordinater:
Beregnet Forskjel mellem Theriuonieteratlæsningerne opconstru-
Tlie case is very different when the temperature
increases rapidly with the depth. A water-soaked wooden
frame can then cause the thermometer to register utterly
erroneous temperatures. We had a striking example of
this tact at Station No. 375. At a depth of 17») fathoms
the mercury-piezometer indicated a temperature of 2". 40.
At the bottom, in a depth of 204 fathoms, accordingly
not more than 34 fathoms deeper, the mercury-piezometer
indicated — 0°.nl and the Miller-Casella No. 1 — 0".33.
after reducing both instruments for error of scale and
for pressure. The inverting-thermometer, Negretti and
Zambra No. 89, registered <>".49. or almost a whole degree
too high. The same phenomenon was observed at Stations
327. 328, and 338. As early as the first days ol’ our
cruise in the Barents Sea. these irregularities attracted my
attention, and therefore I had an index-thermometer
invariably sent down with Negretti A’ Zambra’s instrument.
No sooner had the wooden cases got soaked through with
water than I ordered the carpenter to make new ones,
which were used for the minor depths, so long as. after
careful testing in sea-waiter, they had been found to retain
their buoyancy. The water-soaked cases were made use
of for greater depths only. It is not possible by means of
paint or varnish to protect the wooden cases, and thus
prevent them from losing their buoyancy. Nor is it possible
to restore buoyancy to the water-soaked cases by drying
or giving them a. covering of some kind or other. Pieces
of cork are of use, but only for a time. Strong glass
tubes, sealed at the ends, may serve, when put in the
cases, to counteract these drawbacks. At present, however,
preference will generally be given some one of the
various kinds of inverting-inechanism, recently devised, which
cause the instrument to turn over on hauling in tin1 line,
by means of a propelling screw, and then prevent it from
turning back again. This is a matter of importance
with series of temperatures, if several thermometers are
attached to the sounding-line at different depths and a
sea is running. Under such circumstances there is
danger, with the wooden cases, of an
inverting-thermometer that has already registered the temperature turning
over again, on a higher level, when the vessel dips in
the sea.
To find how long a time the various kinds of
deep-sea thermometers require to take the temperature of the
surrounding water. I instituted a series of experiments. The
thermometer to be tested was placed either in water or a
mixture of snow and water, after having first been given
a. higher temperature. A standard-thermometer indicated
the temperature of the water. Both thermometers were
allowed to remain undisturbed in the Huid, which 1
did not stir. At given intervals the deep-sea
thermometer was read off. an assistant noting simultaneously
the time by a watch, and immediately after the
standard-thermometer. For every reading, the difference was
computed between the indications of the two
thermometers. This operation I continued till tin- said »lifter
ence proved to be constant. With argument: minutes
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