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B. Observationer i Søen og tieres Resultater.
B. Observations at Sea, and their Results.
Ved Expeditioner^ Udrustning var det paatænkt, at
der skulde gjøres fuldstændige magnetiske Observationer
ombord, naar man var i Søen. Hertil havdes fuldstændigt
Apparat i Admiralitets Standard-Kompasset og
Fox-Cir-kelen. Med denne sidste foretog jeg i 1876, under Skibets
Udrustning, paa Bergens Observatorium de nødvendige
x\f-vejninger. Under Expeditionens Ophold i Husø fra den
10de til 19de Juni samme Aar gjordes alle de fornødne
Basis-Observationer. De magnetiske Elementers Størrelse
bestemtes, som ovenfor vist, i Land ved absolute Maalinger.
Deviationen bestemtes saavel for Styre-Kompasset som for
Fox-Cirkelens Plads og med Fox-Cirkelen maaltes
Inklination og Intensitet under forskjellige anlagte Kurser, idet
Skibet blev svunget ved Hjælp af Trosser. Der toges
Svingnings-Observationer til Bestemmelse af Coefticienterne
f.1 og Å.
Ved Beregningen af de med Fox-Cirkelen ombord
maalte Inklinationer og Intensiteter, fandt Prof. Mohn, at
disse ikke kunde bringes til indbyrdes Harmoni, med mindre
Indexfejlen for Fox-Cirkelens Naal sattes hele 19 Minuter
større, end den fandtes af de Observationer, der var gjorte
i Land paa samme Sted og til samme Tid med
Fox-Cirkelen og med Inklinatoriet.
Da vi den 22de Juni 1876 i meget roligt Vejr og
rolig Sø forsøgte Observationer meel Fox-Cirkelen, viste det
sig, at Skibet, vel nærmest paa Grund af det langsomt
virkende Styreapparat,1 ikke kunele holdes paa Kurs meel
den Støhed, som udfordredes til at Observationerne kunde
gjøres meel nogenlunde Nøjagtighed, ligesom Skibets
vertikale Bevægelser uagtet clen rolige Sø viste sig yderst
hindrende i samme Retning. Beregningen af Observationerne
gav ogsaa et utilfredsstillende Resultat. Kun en Gang
senere forsøgtes, nemlig under Sejladsen ind til Thorshavn,
Observationer meel Fox-Cirkelen. Det yderst urolige Vejr,
som Expeditionen havde i 1876, forbød alle videre Forsøg
i dette Aar.
I 1877 hinelrede saavel Vejret, som den
Omstændighed, at jeg maatte gaa fra Husø til Bergen for at faa
indsat ny Mellemaxel i Maskinen, mig i at foretage
Basis-Observationer. I 1878 var Expeditionen under Rejserne
saa ganske optagen af andre mere nødvendige Gjøremaal,
at eier ikke levnedes Tiel til at tage andre magnetiske
Observationer ombord end til Bestemmelse af Misvisningen.
Saaledes forenede sig Skibets magnetiske Konstitution,
om jeg saa maa kalde elet, dets langsomtvirkende
Styre-apparat, dets Letbevægelighed og ringe Bredde, uroligt
Vejr, Reparation af Maskinen og Hensynet til
Expeditionens Hovedarbejder, Lodninger, Temperäturmaalinger og
Skrabninger, til absolute Hindringer mod Fox-Cirkelens
1 C. Wille. Apparaterne og deres Brug-. Side 4.
The Scheme of Work approved for the Expedition
included complete series of magnetic observations at sea,
for which we had the Admiralty standard compass and the
Fox circle. With the latter instrument, I undertook in
1876, at the Bergen Observatory, whilst the ship was
fitting out, the necessary weighings. During the stay of
the Expedition at Husø, from the 10th to the 19th of June,
same year, were taken all necessary base-observations. The
eleviation was determineel alike for the steering-compass and
the position of the Fox circle, and inclination and intensity
were observed with the Fox circle on different courses, the ship
being swung the while by means of hawsers. Observations
of vibration were taken to determine the coefficients f.i and I.
In his computations of inclination anel intensity
observed on board with the Fox circle, Professor Mohn could
not, lie found, attain satisfactory agreement for the
respective results unless the index-error for the needle of the
Fox circle were put as much as 19 minutes greater than
the error found from the observations taken on shore in
the same place and at the same time with the Fox circle
anel with the dip circle.
On taking a few preliminary observations with the Fox
circle, June 22nd 1876, in very fine weather and a calm
sea, it was found impossible, chiefly no doubt owing to the
tardy action of the steering-apparatus,1 to keep the ship
sufficiently steady on her course for observing with
comparative accuracy; moreover, the vertical motion of the
vessel, calm as was the sea, proved a serious obstacle to
the attainment of anything like trustworthy determinations.
The computed results, too, were not to be relied, upon.
Only once afterwards, viz. when nearing Thorshavn, did
we try to observe with the Fox circle; indeed the
boisterous weather encountered by the Expedition throughout the
summer of 1876, precluded any further attempt on the
first cruise.
In 1877 I had no opportunity of taking
base-obser-vations, both by reason of the weather anel the eliscovery,
on arriving at Husø, of a defect in the engine-shaft,
necessitating our immediate return to Bergen to get a new one
put in. In 1878 the prosecution of other anel more
important exploratory work left no time for magnetic
observations save those required to determine declination.
Thus, the ship’s magnetic properties, so to speak, the
slow action of lier steering-apparatus, her great mobility
and trifling breadth of beam, rough weather, time lost in
repairing the engine, anel regard to the main objects of
the Expedition, viz. sounding, determining temperature, and
elreelging the bottom, — proveel one with the other in-
1 C. Wille. The Apparatus, and How Used, p. -1.
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