THE LONGITUDE BY TELEGRAPH.
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with the coast survey, having proven altogether successful
we have now the satisfaction Of laying the following very in
ierestng paper upon that subject before readers We
commend IT. at the me the astronomers and engi-
neers beyond the Atlantic Union
DIFFERENCE OF LONGITUDE BY TELEGRAPH.


one o. the earliest uses Of Moses Electro gnetc Tee-
graph was that OF determining geographical longitude
few signals passed between Washington and Baltmore
IN 1914, under the direction of Capt Wilkes by carving
chonomeers from astronomical stations the telegraph Offices
But the most complete trial Of this method extant has recent
y been made under the direction of the present
dent Of the United States survey Professor Bache


In the autumn of ls45 arrangements were for
making an experiment the whole of the line from
Jersey City to Washington distance of $50 miles I'm
medatey after the completion of the line in S46 trials were
made The violent storms OF the autumn and the continual
repairs along these new lines prevented complete success in
ie4o Accordingly, in the months of July and August Of
this year operations resumed the new and more per
fectly insulated lines.


Professor Bache had built at the expense of the survey


line from the Washington post Office the National Obser-
vatoy He had procured the three Of Wash
lngton, Philadelphia and Jersey City, full complete ee-
graph apparatus, and had connected them with the main ne
50 as to make these obsevatoes temporary telegraph offices
having rented the line Of the Telegraph Company for asro
nomcal purposes only Professor Bache had ALSO at the ex
pense OF the survey erected the temporary observatory at
Jersey CITY, and engaged the services Of Professor Loon
the late distinguished director of the Western Reserve Obse
vatory, now IN the chair of physics the New York Uni
versy He had also engaged the of Professor KEN
DALI the director of the observatory Of the Central High





OF the National Observatory, had, early in Is45 rendered to
Professor Bache the cooperation of that establishment The
arrangement OF the details Of the work entrusted to Sears
T. Walker of the the survey Il is under
stood that full and detailed report Of these operations will
be made this autumn by the superintendent to the Secretary
OF the Treasury As partial notices of the work have
already found their way prematurey into the public prints,
we are authorized to lay before readers an authentic
form, general view Of the Of these operations of
which the results will, in proper time, be made public


Ihe clocks at the observaores having been carefully egu-
"a hx ~
session of the line for the night is given to the asrono-
mers and skiul operators accompany them station


The performances Of the Sd of August, ls47, may be
quoted example of successful nights work The
source OF electrical power Groves constant battery
having ortyour halfpnt cups The magnets were adjust
ed by the operators and twenty clock signals given by
Mr. Zantznger the operator at Jersey City, intervals Of
ten seconds EACH and at condolences with the clock BEATS
These twenty signals were compared with the Jersey City
clock by Professor Loom and by Professor Hubbard IT, s.
Navy, (hen on visit to Jersey City, The same twenty
were received and compared with the clock of the Phlade
Phia Observatory by three Observers Messrs Walker Rey-
nolds and Mason, professor Kendall being absent The
same set OF twenty signals also received and compared
with the clock the Washington Observatory by Professor
Keith, the officer charged with this duty by Lieut. Maury


In the same manner the twenty signals from Philadelphia
and rem Washington recorded the three stations II
known that no two Observers with the instru-
nent and clock, obtain for the correction Each has
his peculiar habit of seeing hearing 1t became necessa-
y for all the observers to meet together and make obser
vaons at the same place. the evening, with the





correction to normal or average value.


Alter applying this correction for the pecuaes of the OBJ
servers 1t be presumed from the excellence Of the nsu-
mens and experience of the Observers that the corrected clocks
at Washington, Philadelphia and Jersey City indicated the
true sderea time of these merdians within quarter-per-
haps within tenth part-of second.


The method adopted Of observing zenith before and
alter reversal OF the transit instrument gives the clock
time, after correcting for personal equations precision little
short of the actual leveng. Now with the levels in use at
these places second OF arc or seventy feet of longitude
represented by line, tenth inch The precision of
full nights work may be readily reduced within forty feet so
lar as the levelling instrument is concerned.


III these clocks chronometers corrected could be sud-
denly brought sdeby side without derangng their motions,
simple comparison of their corrected readings for the same in
slant Of time would give the difference of longitude with pre-
cson not far short of the clock themselves or of
the evens observations on which they chiefly depend This
method forms the basis OF the chronometer expeditions of
which extensive and successful made by Robert Treat
Paine, Esq, in the Massachusetts survey


is in the that the observaores Liverpool
England and of Cambridge, New England have been con-
necied together by Wm Canch Bond ESQ., by means Of the
chronometers of the Liverpool steamers.


But the magnetic telegraph method dpenses with the trans
portaon of chronometers and only transports the essential
portion viz. the clock beat ITSELF


The practsed observer readily strike on his KEY with
such precision tina, the delicate cannot distinguish
any want of accord between the clock key beats
This method of beating time resembles the process the lead
er of an orchestra.


So far then, the giving of signals concerned no error
need be appehended But the party who another obse





codng the best of his Judgment is liable three separate
and independent of error


The first is in the time (if amy employed by the electro
magnetic fluid, wave, in traversng for instance the two
hundred and fifty miles of the wire that connects the Wash
ngon and Jersey City observatores.


The second is the time that eapses after the fluid or wave
has aversed the interval and commenced the induction of
magnetic action in the receiving magnet before il brings
the armaure and beat that recorded
by the receiving observer.


The third the committed by the receiving observer
noting the fraction oa second between the clock beats pre-
ceding and following his armature beat.


From this enumeration of the sources of error il appears
that when take the of the two values for the onpi-
ude between two obscrvaores by the eastern and the es
Signals the result requires four corrections one is for the
difference, personal equaton of the clock corrections
one for that of clock nongs third is for that Of circuit
lime, (asronomcay, alteration time y and fourth for that
of arndture fine.


The first Two corrections asceaned by bringing the
Two observers together The Of the other may be
obtained by subtracng the longitude by signals from
The longitude by eSfrn signals Half the remainder the
sum Of the two circuit times and of the two arraature
times.


Now the more the experiments repeated, and the
greater the bestowed hem the nearly does the
sum of these four approach to nohpg The concu-
sion from this circumstance irresistible If sum of
bese two pairs of quantities Gall posive snapprocabe the
difference between the two similar individuals Of these s is
Tor stronger reason, insensbc


The number Of clock signals transmitted along the line is