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Siile
tog jeg den 22. August 1878 i Advent Baj, Spidsbergen,
i 15 Favnes Dyb ved 0°.9 og i Overfladen ved 4°.8.
Den 20. November 187.S prøvedes samtlige Nulpunkter ved
det meteorologiske Institut i Christiania i smeltende Sne.
Denne og følgende Dag foretoges Sammenligninger ved
højere Temperaturer mellem Dybvandsthermometrene og
Xornialthermometret.
Ved Indexthennometrene er jeg af Erfaring bragt til
at gjøre følgende Bemerkninger. Ved de ældste
Miller-Casella-Thermometre (I—IX) staar Skalaen med
Gradinddelingen red Siden af Thermometerrøret, Dette gjør
Aflæsningen noget vanskelig, naar den yderste
Nøjagtighed søges opnaaet. Gradskalaen var fæstet til
Ebonitpladen med en Skrue i hver Ende. Man maa passe vel
paa, at disse Skruer ikke ere løse. da der i dette
Tilfælde kan opstaa en Usikkerhed ved alle Aflæsninger paa
flere Tiendedele af en Grad. Ved Forsøg, anstillede paa
disse Thermometre, medens de vare omgivne af smeltende
Sne, fandt jeg den 29. November 1879, at der var en
ganske liden Forskjel paa Aflæsningen, enten jeg aflæste
den frie Kviksølvtop eller den til samme med Magneten
nedtrukne Index. Denne viste sig at trykke Kviksølvtoppen
flad, og gav saaledes en højere Temperatur. Correctionen
beløb sig i Middel for sex Thermometre til -†- 0.03 +
(•".011. Ved de Aflæsninger, der ved Sammenligningerne
mod Norinalthermoinetret eller ved Nulpunktbestemmelsen
ere gjorte paa Kviksølvtoppen, er denne bleven corrigeret
mod -f- 0".03 forat faa den Aflæsning, der svarer til
In-doxens nedre Ende. Dot or de saaledes corrigerede Tal,
som ere opførte i do følgende Tabeller.
En Ulejlighed ved Indexthennometrene or, at
Kvik-solvtraadcn undertiden splitter sig. Dotto kan i Regelen
lot rettes paa ved at svinge Instrumentet i en Slynge med
Kuglen inderst. Centrifugalkraften driver da Kviksølvet
sammen paa dets rette Plads. Undertiden sidder Indexen
saa fast, at en Magnet ikko formaar at flytte den. I
saadanne Tilfælder har jog mod Hold brugt to olier tre
Magneter, enten en paa hvor Side af Roret — som dot
undertiden var nødvendigt at løsne fra Indfatningen — olier
som magnetisk Magazin. Værre er det, uaar Kviksolvet
or kommet forbi Indexen og holt eller delvis indeslutter
denne, thi da formaa Magneterne ikke at drage den ud
deraf. I saadanne Tilfælder, naar Centrifugalkraftens
Anvendelse ikko har forstaaet, har jog med Held brugt den
Fremgangsmaade at afkjøle Thcrmonietorkuglon, undertiden
vod Hjolp af fordunstende Æther. Kviksølvet — paa
Minimumsiden, som jog her altid har for Øje — trænger
da ind i Kuglen eller don under samme van-ende
Kaliberudvidelse, samler sig i dennes nederste Dol med en mindre
Højde og on større Diameter og lader Indexen saa fri,
at den kan extraheres mod Magnet. Ved den følgende
ditions as those under which the actual observations were
made. On the 22nd of August 1^78, I made a similar
experiment in Advent Bay Spitzbergen, at a depth of
15 fathoms, temperature 0".9, and at the surface of the
sea, temperature 4°.8. On the 29th of November 1878,
the zero-points of all the thermometers were tested at
the Meteorological Institute in Christiania, by immersing
the instruments in molting snow. On this and the
following day, comparisons wore undertaken at higher
temperatures between tlio deep-sea thermometers and the
Standard-Thermonieter.
As to the index-thermometers, experience has lod mo
to make the following remarks. The oldest Millor-Casolla
instruments (I—IX) have the graded scale at the side of
the tube. This renders the reading somewhat difficult
when great accuracy is sought to be attained. The
scale was made fast to an ebonite plato by means
of a screw at either end. Care must be taken
lost those screws got loose; for if they do, an
uncertainty to the extent of several tenths of a degree may
arise in all the readings. When experimenting with
these thermometers, on the 29th of November 1879,
whilst they were immersed in molting snow, I found
a very slight difference in the reading whether
I read the free upper surface of the mercury or
the index drawn down to the latter by the magnet.
The index was found to press the surface of the
mercury flat; and hence it indicated a higher
temperature. The correction amounted in the mean for six
thermometers to -f- 0°.03 + 0U.0U. When reading off the
upper surface of the mercury — for comparisons with
the Standard-Thermometer or determining zero-points —
a correction of -f- 0".03 has been applied, in order to
obtain the reading that corresponds to the lower end of the
index. The figures thus corrected are those given in tho
following Tables.
Ono inconvenience attaching to tho index-thermometers,
is that the thread of mercury will sometimes break. This
can as a rule be easily rectified by swinging tho
instrument in a sling, with the bull) inwards. Tho centrifugal
force will then force back the mercury into its right
position. Occasionally the index gets jammed, so that one
magnet is quito unable to move it. When such is the
caso, I have successfully mado use of two or three
magnets, either one on each side of the tube — which it
sometimes proved necessary to loosen from the frame — or as
a magnetic magazine. It is a matter of far greater
perplexity when the mercury has passed tho index and either
wholly or in part surrounds the latter; for the magnet is
thou powerless to draw it out. In such cases — the
application of centrifugal force being found insufficient — I
have resorted with success to the following mode of
procedure, viz., that of cooling the bulb of the thermometer,
occasionally by means of evaporating ether. The
mercury — that on tho minimum-side, which is always to be
understood — pushes through into the bulb or the expansion
of the bore below it. and collects there in tho lowest part with
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