The Anderson intelligencer. [volume] (Anderson Court House, S.C.) 1860-1914, 1899-05-17
TWILIGHT'S LENGTH.
HOW 1T VARIES AT DIFFERENT TIMES
AND PLACES.

HOW 1T VARIES AT DIFFERENT TIMES
AND PLACES.
When 1t Is MT It's Shortest All Over
the Globe, 1t Lasts For Thirty Min
utes at Honolulu and For Eighteen
Days Mt the Poles.
The belief that there is little or no
twilight within the great tropical belt
encircling our planet is a very wide
spread one. History, however, warns
us that beliefs need not necessarily ac.
cord with facts. It might indeed almost
be said that they usually do not.
The toiling and noiling millions, the
humble units that, taken in the bulk.
constitute what is called ssgreat pow
er, have neither the time nor the in
clination to overhaul their opinions.
They are not assailed by doubts as to
whether the intellectual coffee which
they have at odd moments imbibed
may not have been mostly chicory.
Such state Of mind unquestionably
makes more happiness, and although
such happiness may bear rather too
much resemblance to that of, say, the
COW it is none the less real for all that.
Twilight is at its shortest at the
equator and increases with the latitude
-at the equinoxes-at about the same
rate as that at which the meridians de-
crease their distance from one another.
The increase is, therefore, very slow in
low latitudes and very rapid near the
poles
Practical or civil twilight is the time
which elapses between the moment Of
the suns setting and the moment when
he is seven degrees Of a great circle be-
low the horizon. At the equator this
time cannot, Of course, be less than 90
minutes At the edges of the tropic
zone it is about 81 minutes.
A person with good eyesight will,
should he care to make the experiment.,
find that when at sea and on or near
the equator he is able to read average
type on deck for at least 20 minutes
| after the sun has set without the aid of
artificial light and when there is no
moonlight.
This is the common sense experiment
of which the duration is considerably
longer than the practical, and even at
the equator something like 70 minutes
will elapse before night holds undis-
puted sway This is the length of the
true, the astronomical twilight.
1t is at or near the equinoxes that the
phenomenon under consideration is at
its shortest all over the globe At those
| periods it lasts at Honolulu 80 minutes ;
at San Francisco, 35; at London, 40;
at St. Petersburg, 81; at the Arctic and
Antarctic circles, 70, and at the poles,
18 days. When, then, we say that the
poles have six months light and six
months darkness. it is little mere than
facon de parler.
The north pole has no less than 223
days Of practical dayli ght each year, the
south pole, 215 days. and the equator
1877 days. Nansen, when in high north
ern latitudes. was able to read The
Verdensgang many days before the
longed for sunrise following the long
winter night. The great length of the
twilight in polar regions is a boon in
deed to explorers. The popular imagina-
tion usually attaches itself to the great
cold they have to endure, but the real
enemy is the long darkness, which is
trying to the enthusiasm Of even a
Nansen, Peary or a Jackson.
There is practically no difference in
the length of the twilight at the equa-
tor at the equinoxes and solstices. Even
at Honolulu it will not vary by more
than couple of minutes. But in the
higher latitudes the varying duration
is very marked In latitude 5975 de-
grees, for instance, it lasts 56 minutes
at the euuinoxes, but in the summer
solstice it lasts from sunset till sunrise
that is to say, from 9:10 o'clock till
$50. OF FIVE hours and 40 minutes.
/ North or south Of 8S,degrees practical
twilight lasts all "night' at the eqni-
noxe. The sun is, it is true, only IL
hours above the horizon. but as he can
not go more than 7 degrees below it
there is continual daylight for the "a
hours. In such cities as Stockholm. and
st. Petersburg there are close on to IA
hours Of daylight at those seasons when
day and night are said to be equal, and
at the equator itself the day all the
year round is made of ! 8 hours daylight
and II hours darkness. It must not be
forgotten that in those latitudes where
the sun remains for months below the
horizon there is during that period a
good deal Of daylight so that along the
eightieth parallel north IA little north
of which the Jackson-Harmsworth e1-
peditiop spent three consecutive years
in the Franz Josef islands), although
the sun does not rise between Oct: 19
and Feb. 22 there is period of three
weeks following the final sunset and
another Of the same length preceding
the first sunrise Of the year, on each
day of which good type can be read for
few minutes up to some hours with
out artificial light.-San Francisco Call.
Some Curious Clubs.
New York has new feature in clubs
1t is the .Dyspeptic club, and the
! fest of eligibility for membership is a