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11
Deviationen.1 Værdien af B vai’ierede i 1878 fra 22°
(Vardø) til 30° (Nordspidsbergen), eller i det Hele 8°. I
1877 varierede B højst 5°. I dette og det foregaaende
Aar benyttedes de hvert Aar i Husø bestemte
Deviations-værdier. Deviationsprøven i Vestfjorden den 10de August
1877 kunde ikke benyttes til Reduction af dette Aars
Observationer, da nogle Jernmassers Stilling ombord ved den
forsætlig vare noget forandrede. Ved denne Prøve, samt i
1878, var Deviationen 0 for Nord og Syd, og meget nær
Maximum for Øst og Vest.
Den til Vindobservationernes Reduction benyttede
Misvisning er væsentlig taget efter de under selve
Expeditionen af Capt. Wille, dels paa Land, dels paa Søen tagne
Declinationsbestemmelser. Paa det ovenfor under No. 1
nævnte Kart vare Isogoner for hver 5te Grad optrukne
efter de ved Deviationsprøverne fundne Værdier af
Misvisningen. I Land bestemtes Misvisningen i Husø, i
Reykjavik, i Namsos, i Bodø, i Tromsø og i Hammerfest. De
benyttede Værdier af Misvisningen stemme paa det
allernærmeste med det af "Deutsche Seewarte" publicerede
Iso-gonkart-, til hvilket Nordhavs-Expeditionens Resultater ere
benyttede.
Skibets Fart bestemtes i 1876 ved den almindelige
Log eller ved Patentlog, i 1877 og 1878 med ’’Vandloggen".
Om denne indeholder Capt. Willes Afhandling om
"Apparaterne og deres Brug" følgende Beskrivelse:
„Paa et bekvemt Sted i Maskinrummet bores et Hul
i Skibshunden og fores med et 1 Toms Rør. Over dette
anbringes med Flens Røi-et b (se den lille Figur) saaledes,
at Aabningen i dette danner en Fortsættelse af Hullet i
Bunden. Paa Midten af dette Rør er en konisk Kran og
omkring dets øvre Ende er Skruegjænger til Pakningsringen
c. Gjennem Røret b og Hullet i Skibsbunden nedsættes
Røret a saa langt, at den lille Aabning i dets nedre Ende,
der forøvrigt er lukket, kommer omtrent 0.m5 (20 Tommer)
under Skibsbunden og visende ret forefter. Denne Afstand
fandt vi var den hensigtsmæssigste. Eu mindre Afstand
bragte Hullet for nær det af Skibsbunden medslæbte Vand,
en større Afstand rønnede for meget paa det fritstaaende
Rør under større Fart. Pakningsskruen c tilskrues.
Ovenfor c bør Røret a have en mindre Kran d. Fra a’s. øvre
Ende gaar et tyndt Blyrør til Stigerøret g, der har omtrent
lø cm (4 Tommers) Diameter. Dette maa placeres
midtskibs, verticalt og saa lavt, at dets nedre Ende er godt
under laveste (nederste) Vandlinies Plan. Det er forsynet
med Blænde, for at ikke Vandet under Skibets Bevægelse,
skal pumpe i Røret. I dette Stigerør er anbragt en Flyder,
’ Forøvrigt henvises til Capt. Willes Afhandlinger: Om
"Apparaterne og deres Brug", hvor Skibets Navigering er beskrevet, og om
"De magnetiske Observationer" i denne Generalberetning.
2 Annalen der Hydrographie und maritimen Metcorologie 1880.
Heft VII.
value of the deviation1 could be found on Plate 2. The
value of B ranged in 1878 from 22° (Vardø) to 30° (North
Spitzbergen), or 8°. In 1877 the range was scarcely
5°. In this and the previous year we calculated with
the deviation-values found on each cruise at Husø. The
deviation determined in the Vestfjord on the 10th of
August 1877 was of no assistance for reducing that year’s
observations, various masses of iron on board having been
purposely changed in position. On this occasion, as also
in 1878, the deviation was 0 for north, and the maximum
very nearly for due east and west.
The Variation for reducing the wind-observations was
principally taken from Captain Wille’s determinations of
declination, performed during the Expedition, partly on
shore, partly at sea. On Chart 1, mentioned above, the
isogonic lines for every five degrees were drawn in
accordance with the values for variation found from the
observations for determining the deviation. On shore, the
declination was determined at Husø, at Reykjavik, at Namsos,
at Bodø, at Tromsø, and at Hammerfest. The values for
variation agree very closely with those in the Isogonic Chart
published by "Deutsche Seewarte,"’2 for which the results
of the Norwegian North-Atlantic Expedition have been
adopted.,
The Rate of the Ship was determined in 1876 by the
ordinary log or by the patent log; in 1877 and 1878, by
the "water-log." Of this instrument Captain Wille has
given the following description in his Memoir on "The
Apparatus, and How used": —
"In some convenient spot in the engine-room, a hole
was bored in the ship’s bottom to receive a one-inch metal
tube, having fixed on to its top end the flange of the tube
b (see small Figure), in such manner that the bore of the
latter would form a continuation of the hole in the ship’s
bottom. This tube had a conical stop-cock, and its upper
extremity screw-threads fitting into the gland c. The tube
a was passed through the tube b and the hole in the ship’s
bottom, till the small aperture at its lower end, which for
the rest was closed up, had been made to project about
20 inches beneath the bottom of the vessel, while pointing
straight forward. This we found, by repeated experiment,
to be the right distance. If diminished, it would bring the
aperture too near the water carried along by adhesion to
the ship’s bottom; and if increased, it would, with greater
speed, expose the projecting tube to a serious strain. The
gland c has now to be screwed on. A little above the
gland, the tube a should have a smaller stop-cock d. From
the top of a a slender leaden pipe led to the upper tube
g, which had a diameter of nearly 4 inches. This tube
must be given a vertical position amidships, and far enough
1 For the rest, the reader is referred to Captain Wille’s Memoir
on "The Apparatus, and How used," in which the navigation of the
ship will be found described, and to his "Magnetic Observations,"
both published in the General Report.
2 Annalen der Hydrographie und raaritimen Meteorologie, 1880.
Heft VII.
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