Oxford Democrat. [volume] (Paris, Me.) 1833-1933, 1881-11-01
LONGITUDE ONE HUNDRED AND
EIGHTY.

Among seamen in general, there arr
two meridians Of special interest. ON
is the line of longitude which passe
through Greenwich; and this is calle'
Longitude Naught. The other Of thes'
two meridians might be termed Longi
tude Naughty; because it often confuse'
the ideas OF the passengers who nov
cross the Pacific Ocean from California t.
China, Japan and Australia.
Now, if any young readers have no
studied the subject of longitude. they
will find it profitable and interesting tC
do so, and find out about this thing
Longitude is defined by imaginary lines
called meridians, drawn lengthwise ovel
the earths surface and meeting at Its
poles, thus dividing the surface of the
globe into three hundred and sixty parts,
or degrees, called longitude.
OF course, any one of these meridians
might have been taken as the point &c
star, from in calculating longitues; but,
since the English. as q people. held the
highest position in astronomy, navigation
and chartmaking, they naturally chose
TO represent the first meridian as drawn
through their royal observatory at Green
wich, aud 1t is now generally recognized
as the first meridian; 50 that, as was I'M
piled in the beginning of this article, ali
longitude is practically reckoned east OF
west from Greenwich. Now, as longl-
tude is reckoned from the meridian OF
Greenwich, so the hours of time may be
said to begin again a, the meridian OF
$50 which is exactly opposite, on the
other side OF the globe.
Longitude is calculated by time. and
in this way When a navigator wishes
to know the longitude his ship is IN, he
finds by observation OF The sun or other
heavenly bodies the true time OF day
at the ship. He then compares this with
the time At Greenwich, shown by his
chronometer, and thus he gets his longl-
tude in time, that is, in hours, minutes,
and seconds, which he turns into degrees
of longitude by multiplying by fifteen ;
for, as each of the earth's $50 meildians
of longitude is rolled directly under the
sun once in every twenty hours,
then 500 degrees of longitude must be
equal TO twenty-iour hours OF time, or ID
degrees Of longitude TO one hour Of time,
There is no such thing as "a o'clock
for We reckon twelve hours before noon
and twelve nous after noon and so, also,
there is no 360th degree Of longitude, but
1902 cas-, and $50 . west, making to-
gether 500 degrees.
Now, the apparent noon, or twelve
o'clock apparent time al any given place
IS the time when the earth, 10y her rotary
motion from west TO east, rolls the nerd
ian Of ,ha, given place directly under the
sun, and therefore the meridian OF Green
wich comes under the sun one hour soon
er than the meridian OF l5 west SO,
when il is twelve o'clock, or noon, al
Greenwich or any other place on the
meridian of longitude naught for all
places in the same longitude have the
same time, no matter what their latitude
may be it will be eleven o clock forenoon
at all places in longitude Is : west, con-
sequen,ly, only ten o'clock forenoon in
longitude so west, 9 o'clock forenoon
longitude 4j west, and so on. counting
back one hour OF time for every fifteen de-
erees OF longitude. Thus we find the
when we get across the Western Henri
sphere 10 longitude $50 we are II hour:
behind the time at Greenwich; or, when Il
is noon on January ls,, al Greenwich, II Is
midnight, or JUS, the commencement o.
January ls,, at the longitude OF $50
But, for the same reason, by the rotation
of the earth from west to east, any place
in l5o east longitude will come under
the sun one hour before Greenwich; or
it will be one clock in the afternoon a
those places when il is only noon at Green
wich. and so, counting across the Eastern
Hemisphere. one hour ahead OF Green
wich for every fifteen degrees OF longl
tude, we come to the longitude Of $50
twelve hours ahead of Greenwich time.
Now, on January LIST, it is midnight
or the end of January lst, say, for In
stance, one inch on the ,cest side of mer
idian lS0o. But we have just seer
that, at that very same time that Is
noon, January lst at. say. one inch OF
the east side Of meridian $50 :; so tha
there is twenty -four hours, or one whole
day, difference in time between two per
sons supposed to be standing. one imme
diately on the cas-, side, the other imme
diately on the west side of lSO :; and so
while it is noon Of January lst with th'
one at the east, it would be within few
minutes of noon, January 2nd, with TIT
one at the west. Therefore, by stepping
across the meridian, the day of the weel
and the date would be changed. Th'
one who stepped from east to west woul'
lose day, and the other, stepping from
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