The Press.
London, England, 1854-09-16 00:00:00

SEPTEMRER 16, 1854.

LONGITUDES OF GREENWICH AND PARIS.
EXPERIMENTS have been for some time in progress,
with the aid of electric telegraphs, to determine the
difference of the longitude of the Greenwich and
Paris Observatories in a more accurate degree than
had been previously accomplished, or than was pos-
sible, before the two terminal points had been placed
in instantaneous communication by means of the
galvanic wires. The completion and result of these
experiments are now announced by Professor Airey.
After describing the character of previous endeavours
to solve the problem by actual measurement through
a series of triangulations; by chronometers ; or by
interchanging a number of rocket•signals from station
to station between Greenwich and Paris, the Astro-
nomer Royal continues :

" No sooner did there appear to be a reasonable pros-
pect of success for the submarine telegraph, than the as-
tronomical authorities (the Astronomer Royal on the Bri-
tish side, and M. Arago and the Bureau des Longitudes on
the French side) addressed themselves to the Submarine
Telegraph Company, with the view of establishing a con-
nection by galvanic telegraphs between the two observato-
ries. By that company their applications were received in
the most liberal manner. The company's wires were
placed at the service of the observatories at the hours
most convenient for them ; the connections of wires ( when
necessary) were made by the company's officers, and no
remuneration of any kind was expected. For the actual
conduct of the observations it was necessary to employ in
each observatory a considerable force of galvanic batteries,
and the Electric Telegraph Company, forgetting all com-
mercial rivalry, supplied all that was required at the
Greenwich Observatory. The observatories were, in fact,
chargeable with no expense, except that of laying down
their own short junction-wires to connect the observatories
with the main lines, and that of employing their assist-
ants to make the observations.
" The death of M. Arago delayed the French prepara-
tions so long that a series of observations, directed to a
similar object, was first carried on with the observatory of
Brussels. As soon, however, as M. Le Ferrier was estab-
lished in the superintendence of the Paris Observatory,
the interchange of signals between the Greenwich and
Paris Observatories was organised. It is not necessary to
fp into details upon the method employed, or the extent to
which it was carried. It will suffice to say that several thousand
signals were interchanged ; so many, in fact, as to permit
of the rejection of the larger portion, retaining only those
(to the number of nearly 10,000) which were considered
to be made under unexceptionable circumstances. The con-
trast of this number with that of the rocket signals on
which the determination of 18211 depended is striking.
But the difference in the quality of the individual signals
is not less striking. The result of a single signal given by
the galvanic telegraph is perhaps as accurate as the mean
of all the results of the former operation. It is unneces-
sary, therefore, to say that no comparison can be made be-
tween the di&rence of longitude concluded from the for-
mer observations, and that found from the mass of the
late signals. The former determination is now shown to
he erroneous by almost a second of time* (a large quantity
in astronomy), and this correction is nearly certain to its
hundredth part For this gain of accuracy, this veritable
advance of science, we are indebted, in the first instance,
to the power of commercial associations of which we have
spoken. The power, however, would have availed little if
the possessors of it had not been willing to allow it to be
used for the benefit of society, in the precise way which
the professional men indicated. And it is most honour.
able to our great commercial bodies that they have practi-
cally shown so much readiness to aid in enterprises of
s:ientific character, that accredited men of science feel no
difficulty in asking their assistance."