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Stand er bestemt ved Tidssignaler. Den sandsynlige Fejl
eller Afvigelse fra den absolut jevne Gang sætter jeg, da
den midlere Gang hos Chronometret’ Reid viser sig saa
ud-merket jevn. til + 0/25 (D7).
Den galvaniske Strøm, ved hvilken Tidssignalerne
gives, gaar. ikke directe gjennem alle Stationers Apparater,
men sendes ved Overdrag videre fra visse
Overdrags-stationer. For de Stationers Vedkommende, hvorom
heier Spørgsmaal, er der Overdrag i Christiania, Throndhjem,
Lødingen og Kistrand. Ved Overdragene lider Signalet
en Forsinkelse. Størrelsen af denne lik jeg ved
Telegraf-direktør Nielsen’s og Telegrafintendant Colletts Velvilje
bestemt paa følgende Maade: Strømmen sendtes fra
Christiania over Throndhjem til Lødingen og tilbage til
Christiania ad to forskjellige Traade med 3 Overdrag paa Vejen.
Det med en Nøgel givne Signal kom igjen og hørtes paa
et ved Siden af Afsenclelsesapparatet staaende Apparat.
Naar jeg signalerede med Nøglen i Takt og Coincidents
med mit Lommechronometer. hørtes det tilbagekommende
Signal midt imellem de med Nøglen givne Signaler. Da
mit Uhr slaar 4 Tiendedels Secunder, var Signalets
Forsinkelse 0/20 for 3 Overdrag. Sættes Forsinkelsen lige
stor for hvert Overdrag, bliver den 0/07 for hvert, og
altsaa for 2 Overdrag 0/14. .og for 4 Overdrag 0/28.
Ved Beregningen af Normalpendelens Angivelse for
Signaløjeblikket er gaaet ud fra en Tidsforskjel af O’1 42’" 54/5
mellem Christiania og Greenwich. Efter den af Prof.
Auwers i Geographisches Jahrbuch für 1880 givne Tabel
over de vigtigste Observatoriers Bredde og Længde er den
nævnte Tidsforskjel 0* 42m 53/8. Forskjellen mellem de
to Tal beror paa de nyere telegrafiske Bestemmelser af
Længden af Kjøbenhavns Observatorium, med hvilket
Christianias er forbundet chronometrisk. Idet jeg gaar ud fra
den nyere Bestemmelse, bliver følgelig Klokkeslettet i
Greenwich i Signaløjeblikket 0/7 større end oprindelig antaget.
Observator Geelmuyden har velvilligen meddelt mig
de corrigerede Tidspunkter for Signalernes Afsendelse, der
ere beregnede efter Tidsbestemmelser gjorte saavel før som
efter Signalernes Afsendelse. Den følgende Tabel viser de
efter de oven anførte Correctioner, Strømtid,
Længdecorrec-tion og senere Tidsbestemmelser, rettede Signaløjeblikke,
som ere observerede under Expeditionen, samt
Hovedchrono-metrenes Stand og Gang.
at which its error was found by the time-signals. The
probable error or deviation from a uniform rate, I shall
put — the mean rate of the Reid chronometer having
proved so remarkably uniform — at + 0/25 i.Z)7).
The galvanic current by which the time-signals are
transmitted, does not reach every station direct, being sent
on by relays from certain stations selected for that
purpose. As regards the’ stations at which the time-signals
were observed on the Expedition, the relay-stations were
at Christiania, Throndhjem. Lödingen, and Kistrand. These
breaks occasion some loss of time in transmitting the signal.
The approximate extent of the delay I was enabled by the
kindness of Mr. Nielsen, Director of Telegraphs, and of Mr. Collett,
Electrician, to determine as follows: — The galvanic current
was transmitted from Christiania, via Throndhjem, to
Lödingen, and thence back to Christiania, by two different
wires, and broken by three relays. The signal, given with
a key, came back, being distinctly delivered from another
apparatus, also standing beside the observer. When
signalling with the key, its clicks coinciding with the beats
of my pocket-chronometer, the returning signal would be
heard at the mid-point of the interval between two*
successive signals given with the key. Now, as my
pocket-chronometer beats four-tenths of a second, the delay in
transmitting a signal must have been 0/20 with three relays;
hence, with one relay, assuming it equal for each, the
delay will be 0/07. with two- relays 0/14. and with
four 0/28.
In computing the indication of the. standard-clock for
the moment of the despatch of a signal, the difference in
time between Christiania and Greenwich has been put at
01, 42™ 54/5. According to the Table furnished by
Professor Auwers in Geographisches Jahrbuch for 1880.
showing the latitude and longitunde of the chief Observatories,
the difference is 0A 42m 53/8. The want of agrement in
the respective figures must be ascribed to the late
telegraphic determination of the longitude of the Copenhagen
Observatory, with which that at Christiania is
chronome-trically connected. Taking the latter of the .two
determinations. the assumed Greenwich time at the moment of
despatch will require a correction of -f- 0/7.
Mr. Geelmuyden, of the Christiania Observatory,
has kindly furnished me with the corrected moments for
the despatch of the signals, computed from transists
observed alike before and after transmission. In the
following Table will be found the moments of despatch for the
signals observed on the Expedition, corrected for the
above-specified errors, viz. the propagation of the current,
correction of assumed longitude, and subsquent determinations of
clock error — as also the error and rate of the chief
chronometers.
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