Iowa voter. [volume] (Knoxville, Iowa) 1867-1874, 1873-09-04
GREENWICH TINE.

NEVER had science more pleasant re-
treat than Greenwich Observatory appears
to be. this bright summer morning.
For all its pleasant aspect, however,
the idea of exploring it is decidedly a
formidable one At the very entrance
gates, one feels suddenly convicted of the
most abiect ignorance. Here are myster-
iOus metal pins fixed on the wall for the
determination of British measurements,
and the question at once arises, What have
these to do with astronomy? Then there
is great clock dial on which the hours
are reckoned from one to twenty-four, and
which is popularity believed to be kept
going by the sun.
Determined to clear the way as he goes
on, the visitor makes these outer Difficult
ties the subjects of his first inquiries on
gaining admittance, and he discovers to
his amazement that the very length ofhis
trousers, and the cut of his coat, and the
height of his hat have all been determin-
ed by measurements based upon the mo-
tons of the heavenly bodies.
A tailor's yard measure, it appears,
bears a certain proportion to the length OF
a pendulum which, under specified condl.
tons, beats accurate seconds OF time, and
seconds of time are determined by astro-
nOmical observation. If the tailor wishes
to verify his measure he has only to bring
it to the Observatory gate, where he will
find a standard absolutely accurate. AS
to the clock, it is an astronomers clock,
and astronomers know nothing of a. m. 8
and D. ms; their calculations are suffic-
iently complicated without them. The
notion that it is kept going by the sun is,
it need hardly be said, mere delusion.
I'm ho mortal
servatOry, the visitor finds himself in an
open courtyard, with an irregular pile of
buildings on his left hand. Entering a
low doorway in one of these, he is at once
interested to discover that he is really at
what may be considered the fountain
head of all our computations Of time. The
chief business of Greenwich, as all the
world knows, is to tell us the time OF day,
and in this small and somewhat mean
looking apartment is the great telescope
by which observations for this purpose
are effected.
This instrument-the transit circle as it
is technically called-is twelve feet in
length, and its largest glass is eight inches
in diameter. 1t is suspended by the mid
die between two massive stone buttresses
in such manner as to permit OF its
sweeping the sky in straight line over
head, though it cannot be veered round to
the right or left.
We have arrived, let us suppose, little
before noon the sun is about to cross the
meridian, and an observation is to be
made Shutters in the roof are thrown
open the great telescope is swung up and
fixed in position, and an observer seats
himself at the lower end of it. While we
are waiting for the great luminary, let us
take peep through the instrument. All
that can be seen is a number of vertical
lines-technically called wires, though
they are in reality So many pieces of cob
wed-stretched acr oss the field of Obser-
walton at irregular distances. The center
one is the celebrated meridian of Green
witch, or at all events it represents 1t, and
it is curious to reflect that from this Gen.
ter line ships of all civilized nations, and
in all parts of the known world, are reck-
oning their distances that this little piece
of cobweb is, practically, all that divides
the world into eastern and western hemi-
spheres.
While we are peering along the tele-
scope, the drowsy tinkling of innumerable
clocks is heard through the still summer
air, and we begin to think that for once at
least the sun is behind time. If not, then
it seems plain that all the Greenwich
clocks are wrong, a suppOsition which Is
quite at variance with all our traditional
ideas Of the place. On inquiry, it is graft
flying to find that ::our faith in Greenwich
timepieces is perfectly justified, and that
it really is the sun that is behind time
The apparent motion of the sun, as every
body knows, is really the motion of the
earth. Now the earth moves round the
sun in kind of oval pathway. When
she is on either side Of this oval her
motions are accelerated, and the sun will
cross the meridian before he is due. Just