Weekly national intelligencer. [volume] (Washington [D.C.]) 1841-1869, 1847-08-14
LONGITUDE BY MAGNETIC TELEGRAPH.

The last Annual Report of the Superintendent of
the Coast Survey (ALEx. DALLAS BAcHE) gives an
account of the measures which had
been adopted for the determination of the difference
of longitude between New York, Philadelphia, and
Washington by the magnetic telegraph. The Jour-
nal OF Commerce furnishes the following summary
Of it:
line of wire extended last from the General
Post Office in Washington the Naval Observatory wire
was carried from the High School Observatory in Philadelphia
to the main Baltimore line; and another carried from the
Jersey City Telegraph Office temporary observatory
erected near the Presbyterian church. The observations
Washington under the direction of Mr. s. C. Walker
those at Philadelphia made by Professor Kendall and
those Jersey City by Professor LOOMS Each observer
had at his command good clock, and transit instrument for
regulating it with the greatest precision.
The clocks being properly regulated, all which is needed
for the determination OF the difference of longitude between
these three places is the exhibition OF some signal that
be heard simultaneously each station This is afforded by
the click of magnet which worked in the usual mode of
eegraphng communications. These experiments
menced last season. but only partially successful Sig
exchanged between Philadelphia and Washington
the 10th of October but obtained from Jersey
City.
We understand that these experiments have been resumed
the present season. and that they have been crowned with
The plan of operation learn to be the follow
ing At ten O'Clock in the evening" when the usual business
he Telegraph Company concluded the three Observable
ries above named put communication with each other
They then correspond in the ordinary mode of eegaphng
to ascertain whether the arrangements perfect the OBJ
all ready The observer Jersey City then gives
warning TO prepare for the transmission of clock signals At
the commencement of minute by his clock he strikes kew
(ike the key of piano. and click is heard simultaneously
ut Jersey City, Philadelphia, aud Washington The obsery-
at the three places record the time each his clock
In ten seconds Jersey City again strikes the key click is
heard, and all record the time At the expiration of another
ten seconds third signal given in the manner and
the number of twenty signals After pause of one
minute Philadelphia repeats the series of signals and
all three observers record the time After similar pause
Washington begins and gives another series of twenty sig
nails Thus the three observers obtain sixty comparisons of
their clocks which ought give their difference of time with
almost perfect accuracy This method is beautiful in theory
and apparently very slmpe but great many dsappont
mens have been experienced in reducing practice The
difficulties have however, been surmouned. On the
ing OF the 10Th umo twenty clock signals transmitted
from Jersey City Philadelphia and the same number were
eurned When the computations completed for the
act determination of the time of the respective places these
observations will give the precise difference of Longitude be-
tween Jersey City and the High School Observatory Pha
delphia. According to hasy comparison this difference
amounts to fur minutes and thirty seconds. Since the 10Th
instant similar of signals have been repeatedly passed be-
tween Jersey City and Philadelphia, and the comparisons will
be continued until further increase of accuracy be
expected.
This method of determining longitude was tried upon small
scale between Washington and Baltimore after the
ton of the telegraph wire; with this important difference
however, that the comparison OF time made by of
chronometer carried the telegraph Office In the present
experiments the wire is continuous from the Philadelphia OBJ
servaoy the Jersey City Observatory and the two clocks
be compared with about the precision they
standing side by side IN the
1t probable that this mode Of determining longitude
will supersede every other method between places where
Geographic erected The time required for the passage
of the electric fluid through the distance of hundred
thousand miles, entirely napprecabe and the compare
can be repeated at pleasure until the satisfactory result
obtained We understand is the intention Of the Supen-
enden of the Coast Survey in due time extend this method
to all the principal cities along We
that this method has been attempted in any part of Europe.