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19
For Thermometer No. I have vi C = + Il59,
n.N = 0.105 x 24 = 4- 2.52 og J t = 128.8, hvoraf
Correctionsformelen for No. I for Skala bliver
saaledes
C r= + 0°.I05 — 0.0072 t.
Do efter denne Formel beregnede Va>rdier af
Cor-rectionerne ere opførte i ovenstaaende Tabel linder
Rubrikken B. 1 den sidste Rubrik staar Forskjellen mellem
den observerede og den beregnede Correction : C—B.
Summen af C—B er, uden Hensyn paa Fortegn, 1.27,
og den gjennemsnitlige Van-di, 1.27 : 24. er + 0«.053.
De Miller-Casella’ske Dybvandsthermometre ere
construerede saaledes, at Kuglen er beskyttet mod
Sammentrykning ved Vandets Tryk. Men Thermometerrøret er
udsat for Trykket, der gjør dets Kaliber mindre og driver
Kvilcsølvtraaden bort fra Kuglen, hvorved Aflæsningen giver
en for høj Temperatur. Paa Minimumsiden, hvor Indexen
er nærmest ’Kuglen, bliver denne Virkning af Trykket
ringe, men paa Maximumsiden bliver den merkelig stor,
da Kvilcsølvtraaden, der kun er lidet sanimentrylikelig,
antager en forøget Længde i det indsnevrede Kaliber. De
for Maximumsiden fra Oasella opgivne Trykcorrectioner
for vore Thermometre vare fra 0n.6 til l°.l for 2000
Favnes Vandtryk. Ved vore Undersøgelser benyttedes kun
Minimumsiden. Correetionen for Trykket paa denne har
jeg kunnet bestemme, i 1878, directe for hvert
Indexther-mometer ved Sammenligninger af de paa større Dvb gjorte
Registreringer med, hvad de Negretti-Zambra’ske
Vende-thermometre udviste paa samme Sted og til samme Tid,
idet de sidstes Registreringer ere ganske uafhængige af
Trykket. Ved Lodskuddene paa større Dybder lod jeg
et eller Here Indexthermonietre ledsage til Bunds af et
Vendethermometer og erholdt derved en Række
Sammenligninger til Bestemmelse af Indexthermometrenes
Tryk-correction. Ved Beregningen af denne kan Correctionens
Størrelse uden merkelig Fejl sættes proportional med
Dybden. Den skal, som ovenfor paavist, være negativ. I den
følgende Tabel indeholder den første Rubrik
Loddestätio-nens Nummer, den anden Rubrik Dybden i engelske Favne,
den tredie Rubrik Aflæsningerne af Minimumsindexen paa
Thernionieter No. I, corrigerede for Skalaens Feil efter
den ovenfor givne Formel, den fjerde Rubrik Aflæsningerne
af et af Negretti & Zambras Vendethermometre No. 89
eller No. 91, eorrigerede for Skalafejl (se nedenfor), den
femte Rubrik Forskjellen mellem Tallene i fjerde og tredie
Rubrik eller Indexthermometrets Trvkcorrection.
For Thermometer No. I, we have — C = -f- l.f>9.
11. N = 0.105 X 24 = + 2.52. and t = 128.8; hence
The formula of correction tor No. I (scale) will
accordingly be
C — —|- o°.io5 — 0.0072 t.
The values computed for the corrections according
to this formula have been given in the above Table.
Column B. I11 the last column, the difference between the
observed and the computed correction is C B. The
sum of C —B amounts, without reference to signs, to 1.27,
and the average value. 1.27 : 24, is + 0°.053.
The Miller-Casella deep-sea thermometers are so
constructed as to have the bull) protected from the pressure
of the water. But the tube of the instrument is exposed
to such pressure, which reduces the bore and forces the
thread of quicksilver away from the bulb, whereby the
reading gives too high a temperature. On the
minimum-side, where the index lies nearest the bulb, the effect of
this pressure is but slight ; but 011 the maximum-side il
gets remarkably strong, since the thread of mercury, which
is but very slightly compressible, assumes an increased
length in the contracted bore. The pressure-corrections
given by Casella for our thermometers 011 the
maximum-side, were as high as 0°.0 to l°.l for the pressure
at a depth of 2000 fathoms. With our investigations,
the minimum-side only was used. The pressure-correction
of this side I was able to determine direct, in 1878.
for each index-thermometer, by comparing the registrings
at great depths with the results exhibited by the Negretti
& Zambra inverting-therniometers in the same spot and
at the same time, the registrations of the latter
instruments being wholly independent of pressure. With
soundings undertaken at great depths, I sent down along
with one or more of the index-thermometers an
inverting-thermometer, and thus obtained a series of comparisons
for determining the pressure-correction of the
index-thermometers. When computing the latter, the correction may
be put, without serious error, proportional to the depth.
It should, as stated above, be negative. In the following
Table, the first column contains the numbers of the
Sounding-Stations, the second column, the depth in English
fathoms, the third column, the reading of the
minimum-index for Thermometer No. I, corrected for error of
scale according to the formula given above, the fourth
column, the reading of Negretti & Zambra’s
inverting-thermometer, No. 89 or 91. corrected for error of scale
(see below), the fifth column, the difference between the
figures in the fourth and third columns, or the
pressure-correction of the index-thermometer.
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