The Republican. [volume] (Oakland, Md.) 1877-current, 1880-03-27
LONGITUDE ONE HUNDRED AND
EIGHTY.

AONUAA ODL ONE hONDhED AND
EIGHTY.
Among seamen in general there are
two meridians of special interest. One
is the line of longitude which passes
through Greenwich; and this is called
Longitude Naught. The other of these
two meridians might be termed Longi-
tude Naughty; because it often confuses
the ideas of the passengers who now
cross the Pacific Ocean from California
to China, Japan and Australia.
Now, if any young readers have not
studied the subject of longitude, they
will find it profitable and interesting to
do so, and find out about this thing.
Longitudeis defined by imaginary lines,
called meridians, drawn lengthwise
over the earth's surface and meeting at
its poles, thus dividing the surface of
the globe into three hundred and sixty
parts, or degrees, of longitude.
Of course, any of these meridians
might have been taken as the point to
start from in calculating longitudes;
but, since the English, as people,
held the highest position in astronomy,
navigation and chart-making, they nat
urally chose to represent the first me-
ridian as drawn through their royal OBJ
servatory at Greenwich, and it is now
generally recognized as the first merid-
ian; so that, as was implied in the be-
ginning of this article, all longitude is
practically reckoned east or west from
Greenwich. Now, as longitude is reck-
oned from the meridian of Greenwich,
so the hours of time may be said to be-
gin again at the meridian of 1870 de-
grees, 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
longitude in time, that is, in hours,
minutes and seconds, which he turns
into degrees of longitude by multiply
ing by fifteen; for, as each of the earth S
800 meridians of longitude is rolled
directly under the sun once in every
twenty-four hours, then $50 degrees of
longitude must be equal to twenty-four
hours of time, or fifteen degrees of
longitude to one hour of time.
There is no such thing as twenty
four O'Clock, for we reckon twelve
hours before noon and twelve hours
after noon; and so, also, there is no
360th degree of longitude, but 1870 de-
grees eastand.1S0 degrees west, making
together $50 degrees.
Now, the apparent noon, or twelve
o'clock apparent time at any given
place, is the time when the earth, by
her rotary motion from west to east,
rolls the meridian of that given place
directly under the sun, and therefore
the meridian of Greenwich comes I'M
der the sun one hour sooner than the
meridian of fifteen degrees west. So,
when it is twelve o'clock, or noon, at
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 lati-
tude may beg, it will be eleven o'clock
forenoon at all places in longitude fif-
teen degrees west, consequently, only
ten O'Clock forenoon in longitude thirty
degrees west. nine o'clock forenoon
longitude forty-five degrees west, and
so on, counting back one hour of time
for every fifteen degrees of longitude.
Thus we find that, when we get across
the Western Hemisphere to longitude
$50 degrees, we are twelve hours be-
hind the time at Greenwich; or, when
it is noon on January LIST at Greenwich
it is midnight, or just the commence
ment of January 1st, at the longitude
OF $50 degrees. But for the same rea-
son, by the rotation of the earth from.
west to east, any place in fifteen de-
grees east longitude will come under
the sun one hour before Greenwich; or,
it will be one o'clock in the afternoon
at those places when it is only noon at
Greenwich, and so, counting across the
Eastern Hemisphere, one hour ahead
OF Greenwich for every fifteen degrees
OF longitude, we come to the longitde
OF 1870 degrees, twelve hours ahead of
Greenwich time.
Now, on January 1st, it is midnight,
or the end of January 1st, say, for in
stance, one inch on the WeSt side of
meridian $50 degrees. But we have
just seen that, at that very same time
Chat is, noon, January LIST, at Green
wich). it is only the beginning of JAN
uary 1st t,say, lone inch on the east side
OF meridian $50 degrees; so that there
is twenty-four hours, or one whole day,
difference in time between two persons
supposed to be standing, one immedi-
ately on the east side, the other imme-
diately on the west side of 1870 degrees;
and so, while it is noon of January LIST
with the one at the east, it would be
within few minutes of noon, January
I'd, with the one at the west. There
fore, by stepping across the meridian.
the day of the week and the date would
be changed. The one who stepped from
east to west would lose day, and the
other, stepping from west to east,
would have two successive days of the
same name and date. and so would
gain day. ~
But we have here used the words
east and west as you use them every
day, that is, as directions according To
the points of the compass, and Won
must remember that if we reckon in
that way at the meridian itself. then
the Western Hemisphere lies to the snst
OF the line, and the Eastern H6misDhere !
In fho nf & 1