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210 Latitude & [and] Longitude
the noon observation whould be
wanted to complete the determ-
-ination of the longitude, for
until the latitude was Known
the captain could not be aware
what apparent path the sun
was describeing in the heavens,
and therefor would not Know
the time corresponding to any
solar observation. The reader
can now see that the great
point in finding the longitude
is to have the true time, of
some referance station, in order
that by comparing this time
with ship time, the longitude
East or west of the referance
station may be ascertained.
Ship time can always be
determined by a morning or
afternoon observation of the sun,
or by observing a Known Star,
when toward the East or West,
at which time the diurnal
motion raises or depresses it most
rapidly. The latitude being
known, the time of any given
day at which the sun or a
star should have any particular
altitude is Known also and
therefore conversely, when the
altitude of the sun or a Star
has been noted, the seaman
has learned the time of day.
But to find Washington or
Greenwich time, is another matter,
and without this referance time
ships time teaches nothing as to
the longitude. How then is the
voyager at sea, or in desert places,
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Latitude & [and] Longitude 211
to Know the Exact time at some
fixed station? Most readers Know
that chronometers are used, under
ordinary conditions, for this purpose;
but in long voyages Even the best
chronometers are liable to go astray,
from the continual tossing and
shaking, to which they are subjected,
but especially from the great changes
in temperature which they Endure
when a ship passes from the temper-
-ate loatitudes across the torrid
zone to the temperate zone again.
And then it is to be noted, that
a very insignificant time Error
corresponds to a differance of
longitude, quite sufficient to
occassion a serious Error in the
ships Estimated position. For this
reason it is desireable to have some
means of determining the time at
a fixed station independantly of
chronometers. Any signal which is
recogniseable in whatever way
at both stations, the referance
station nd the station whose
longitude is required, will suffice
to convey the time of one station to
another. Evidently the only signals
available, when telegraphic communication
is impossable, are signals in the
celestial sphere, for there alone can
be discerned simultaineously from
widely differant parts of the Earth.
We know that all
the planets, as well as the sun
and moon, traverse at various
rates and in differant paths,
the sphere of the fixed stars,
But the moon alone moves with
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