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37
af en Observation af Aneroidbarometret. Den støtste
Afvigelse mellem os er 0."""4.
De i Observationstabellerne opførte Barometerhøjder
for 1877 ere Styrmændenes Noteringer af
Aneroidbarometret, reducerede til sand Barometerhøjde ved Havets
Overflade efter de her beskrevne Methoder.
I 1878 anvendtes de samme Barometre, paa den samme
Plads ombord og de samme Control- og Reductionsmethoder
som i 1877.
Som Rejsenormal medfulgte Stationsbarometer Adie
No. 1506, hvis Correction fandtes i Christiania
— O.«" 41 i Mai 1878.
— O. 37 i Oct. 1878.
Den første Værdi er anvendt. Desuden medfulgte
Expeditionen et Fortinsk Barometer af Sécrétan, der oftere
observeredes ved Siden af Adie 1506. naar Skibet laa roligt,
tilsyneladende uden verticale Bevægelser. Dette sidste var
en aldeles nødvendig Betingelse for, at det Fortinske
Barometer skulde kunne benyttes. Der skulde meget liden
vertical Bevægelse til at bringe dette Instrument til at
pumpe. Barometret Sécrétan stemte, naar dets i
Christiania bestemte constante Correction anvendtes, ret godt med
Adie 1506. Men som Controlbarometer var det, ophængt
ombord i et Fartøj i Havne, som Hammerfest, hvor der
næsten altid er en Smule" Dynning, ikke fuldt tjenligt,
hvorfor jeg ved Beregningen ikke har taget Hensyn til de
med samme gjorte Observationer. Stationsbarometret Adie
No. 1506 (Kew Model) derimod, var fortrinlig skikket til
dette Brug, da dets Rør er indsnevret saa vidt, at det
taaler en ganske svag Dynning uden at pumpe, paa samme
Tid som det er langt følsommere end et Søbarometer.
Observationerne med Sécrétan vare dog forsaavidt af Værd,
som de tjente til Control for, at Adie 1506 var i fuld
brugbar Stand.
De første Controlbestemmelser gjordes den 26de Juni
i Vardø, hvor Søbarometret observeredes ombord, medens
jeg under Inspection af den meteorologiske Station
sammesteds observerede Sécrétan i Land. Begge Barometres
Angivelser, reducerede til samme Øjeblik og samme Niveau,
gave for Søbarometret en Correction af — 0.mm62. Da disse
Sammenligninger ikke vare directe, har jeg ikke medtaget
dem i den følgende Tabel,- ihvorvel deres Resultat kommer
overens med det definitive. Den følgende Tabel giver de
Værdier af Søbarometrets Correction, der ere fundne af
directe Sammenligninger ombord, hvor begge Barometre
hang ved Siden af hverandre. Rubrikken •’Lufttryk" er
Observationerne af Adie 1506, reducerede til 0°, og
formindskede med 0.mn,41.
equal to the probable error, given above, of one observation of
the Aneroid barometer. The greatest deviation occurring
between my observations and those of the mates, is 0.mm4.
The height of the barometer given in the Observation
Tables for 1877, is the mates’ readings of the Aneroid
reduced to true barometric pressure at the sea-level,
according to the methods here set forth.
In 1878, the same barometers were made use of,
mounted in the same place on board, and the same methods
of control and reduction applied as in 1877.
As a travelling standard barometer, was taken out on
the Expedition the station barometer Adie No. 1506, the
correction for which had been’ found in Christiania to be
— 0.—41 in May 1878, and
— 0. 37 in Oct. 1878.
The first of these values was applied. Moreover, a
Fortin’s barometer, by Sécrétan, was also taken out on the
Expedition, the readings of which were also noted and
compared with those of Adie No. 1506, when the vessel lay
well-nigh motionless, and apparently without any vertical
movement. The latter condition was indispensible to admit
of observing the Fortin barometer. An exceedingly slight
vertical movement would cause the said instrument to pump.
The barometer Sécrétan was, on applying its constant
correction, determined in Christiania, found to agree pretty well
with Adie No. 1506. Meanwhile, as a control barometer,
mounted on board a vessel in port, — Hammerfest, for
instance, — where there is almost always a little swell, it
did not prove thoroughly serviceable; and hence, in making
the computations, I had no regard to the observations taken
with the said instrument. The standard barometer Adie
No. 1506 (Kew model) was, on the other hand, excellently
adapted for that purpose, its tube being so far contracted,
that it will bear a slight swell without pumping, and is
besides far more sensitive» than a marine barometer. The
observations taken with the Sécrétan instrument proved,
however, so far of value, as they served to show, that the
Adie barometer No. 1506 was in good order.
The first control determinations were made on the
26th of June, at Vardø, where the marine barometer was
observed on board, while I, when engaged in inspecting the
Meteorological Station of that place, observed the Sécrétan
instrument on shore. The readings of both barometers,
reduced to the same moment and to the same level, gave
for the marine barometer a correction of — 0."™62. These
comparisons, however, not having been • undertaken direct,
I have not included them in the following Table,
notwithstanding their result agrees with that definitively found. The
following Table gives the values of the correction determined
for the marine barometer by direct comparison on board,
where the two instruments were mounted side by side.
The Column "Pressure" contains the observations taken
with Adie No. 1506, reduced to 0° and diminished with
0.mm41.
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