The Roanoke times. [volume] (Roanoke, Va.) 1890-1895, 1894-09-14
WHEN THE DAY BEGINS.
How Time Is Measured by Means OF AIerId-
ians OF Longitude

ROW lime Is Measured by Means OF Merld.
ians OF Longitude.
Time Is reckoned by means Of merldi-
ans OF longitude, which aro represented as
imaginary lines extending from polo to
pole on tho earth's surface Whenever the
sun Is directly over ono of these merldians
1t Is noon at all places through which the
line passes. OF course railroad" or
standard" time must not DO COMPOUNDED
with actual time, for by this arbitrary
though very convenient system There are
only four different times from ono coast
to tho other, whereas, according to real or
actual time, every town, village and. city
throughout the Union has different time,
except those that happen to lie in the
Same meridian. AS the earth Is constant
ly revolving from west to east, 1t is con-
tinually bringing different meridian
under tho sun, and as each passes beneath
1t the time Of every place upon tho mcrid-
Ian changes from noon to afternoon, or
from meridian to postmeridian, and the
farther away 1t travels tho later the time
becomes until 1t arrives aG point directly
opposite the sun, when 1t Is midnight.
From this point, then, the meridan be-
gins to travel toward tho sun, and the
time changes to antemeridian until after
journey Of "a hours 1t again reaches the
noon point, and SO on to the end of time.
For tho convenience Of mankind the cir
cumfercnce Of the earth Is divided into
$50 equal parts, known as degrees and the
meridian passing through the observatory
at Greenwich in Londo9 is chosen Us the
center or starting point for the numbering
of these divisions of longitude. Henco the
meridian of Greenwich Is known as lonpi.
tude naught, tho first degree to tho east
being called longitude ono degree cast
and tho first degree to the west being
known as longitude one degree west, and
so on. BY the time we cross tho Atlantic
and reach Philadelphia or Washington
we have got beyond Greenwich to q dis
ance OF, roughly speaking, 75 degrees, or,
In other words, Washington Is said to be
in longitude rs degrees west. If, on the
other hand, we travel across Europe into
Asia for similar distance, we reach a
point rs degrees east.
One degree of longitude is equcl to four
minutes OF time, OF. in other words, every
10 degrees are equal to an hour, so that
when q meridian has passed beyond the
sun for distance of 80 degrees 1t is
o'clock in the afternoon at oil places on
that meridian, or 1t Is 10 o'clock in the
morning II the meridian hos still 80 de-
grces to travel before reaching the point
directly beneath tho sun.
Surprising 1t is midnight on July In
London. longitude naught we will find
that in ST. Petersburg longitude 80 d.
grces cast, it is 2 o'clock in tho morning
of July 4. Fifteen degrees farther east, or
longitude As, it is o'clock in tho morn
ing. AT longitude 60 degrees east 1t is
O'Clock, and so on every Is degrees we
find 1T an hour earlier, until finally, arriv-
ing at longitude $50 degrees cast, we are
exactly ~ hours earlier than London and
on tho other sido of the earth directly op.
posito longitude naught. In other words,
when 1t is midnight of July 4 ut London
1T is 10 O'Clock noon of that day on longi-
tudo $50 degrees east 1t might DO stated,
by tho way, that what wo call noon is in
reality tho beginning of tho day, and all
astronomers SO reckon. -Washington Star