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40
Aneroid B.
Datum (Dan). N T A N—A oba. N—A ber. (comp.) Ob«. — Ber. fot». — Comp.) t
Aug. 11 753-6"" 7-°7 755-6"" — 2.0"" — 2.1m" + O.I"" 0
12 55-2 9- 7 57-0 — 1.8 — 1.8 O.O I
14 56-9 5- 2 59-9 — 3-0 — 2.7 — O.3 3
15 57-7 5- > 60.3 — 2.6 — 2.8 + 0.2 4
i6 56.1 5- 5 58.8 — 27 — 2.6 — O.I 5
■ 7 53-4 6.9 55-3 — 1-9 — 2.2 + O.3 6
i8 53-6 8-5 55-5 - 1-9 — 1-9 O.O 7
’9 54-2 5-6 56.5 — 2.3 — 2.4 + O.I 8
2 I 51-2 5-0 53-6 — 2.4 -2.4 0.0 10
22 49-4 6, 8 51 -5 — 2.1 — 1-9 — 0.2 11
23 49-3 6. 0 51-2 — 1.9 — 2.0 + 0.1 12
24 45-1 4.8 47-1 — 2.0 — 2.0 O.O • 3
Formel (Formula): N= A - 3.™m72 + 0.1801 T + 0.0503 (760 - A) + 0.01291.
e =+ 0.-177, ♂= + (».—118.
Aneroidbarometret B har herefter været meget
tjenligt, og fuldkommen saa godt som A.
Sammenligningen mellem Styrmændenes og mine
Aflæsninger af Aneroidbarometrene i 1878 giver følgende
Resultat. I Gjennemsnit have Styrmændene noteret 0.mm002
lavere end jeg. altsaa en umerkelig Forskjel. Den midlere
Afvigelse mellem os er + 0.mm09 og den største er + 0.mm3.
1878 Aars Barometerobservationer have saaledes i alle
Henseender mindst ligesaa stor Sikkerhed som 1877 Aars.
Efter disse Erfaringer om Aneroidbarometrenes Brug
til Observationer tilsøs tør jeg trygt anbefale at bruge dem,
under Forudsætning af, at der udøves en stadig Control
med dem. Hurtig og bekvem Aflæsning med en
tilstrækkelig Præcision (0.mml), i alle Tilfælder, selv under meget
oprørt Hav, Lethed at anbringe paa et for Observator
bekvemt Sted, Følsomhed for Lufttrykkets Variationer ere
Fordele, som Kviksølvbarometret ikke kan præstere i lige
Grad som Aneroidbarometret ombord i et Skib. Den største
Nøjagtighed vindes ved at bruge Aneroidbarometret som
Observations- og Variationsapparat, og, under dertil egnede
Forhold, at bruge Kviksølvbarometret som absolut
Lufttryks-maaler til Bestemmelse af Variationsapparatets Constanter
og deres Variation med Tiden — samme Princip som ved
Bestemmelsen af Jordmagnetismens Elementer.
Ved Beregningen af Constanterne i Formelen for
Aneroidbarometrets Reduction til Kviksølvbarometret har jeg ikke taget
Hensyn til, at Aneroidbarometret maaler Lufttrykkets Variationer
uafhængig af Tyngden, medens Kviksølvhøjden, ved samme absolute
Lufttryk, er omvendt proportional med Tyngdens Størrelse. I
Formelen skulde istedetfor N, den normale Barometerhøjde, staa Ud-
The Aneroid barometer B proved, accordingly, a most
serviceable instrument, and quite as good as Aneroid A.
A comparison between the mates’ and my own
readings of the Aneroid barometer in 1878. gave the following
result. On an average, the mates were found to have
noted 0."""002 lower than I — an inappreciable difference.
The mean deviation between our notations is + 0.’"m09,
and the greatest + 0.’"m3.
The barometric observations taken in 1878 have,
therefore, an accuracy quite as great as those taken in 1877.
From the experience thus derived in the use of
Aneroid barometers at sea, I can safely recommend these
instruments, provided they are submitted to constant control.
Quick and easy reading, together with adequate precision
(0.mml) in all cases, even in boisterous weather, facility of
mounting the instrument in a convenient place for the
observer, sensibility to the variations of pressure, — such
are the advantages in regard to which the mercury
barometer cannot compare with the Aneroid on board a
vessel at sea. The greatest accuracy is attained by using
the Aneroid barometer as an apparatus for observing the
variations of pressure, and by using, under favourable
circumstances, the mercury barometer to measure the absolute
pressure for determining the constants of the variation
apparatus, — the same principle, accordingly, as adopted for
determining the elements of terrestrial magnetism.
When computing the constants in the formula for the reduction
of the Aneroid to the mercury barometer, I have not had regard to
the circumstance, that the Aneroid measures the variations of
pressure independently of gravity, whereas the height of the mercury
with the same absolute pressure is in inverse proportion to the
intensity of gravity. In the formula, instead of A’, the normal height of the
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