The times., 1899-02-19
DAYLIGHT AND DARKNESS.
Twilight Mt various Degrees of Lat
itudc on the Globes Surface.

(From the San Francisco Chronice)
The belief that there is little or no twi
light within the great tropical belt en-
Circing our planet is very widespread
one. History, however, warns us that be-
liefs need not necessarily accord with
facts. It might. indeed, almost be said
that they usually do not. The toiling and
mo.ling millions. the humble units that,
taken in the bulk. constitute what is called
a great power" have neither the time
nor the inclination to overhaul their opin-
ions. They are not assailed by doubts as
to whether the intellectual coffee which
they have at odd moments imbibed many
not have been mostly cnieury. Such
state of mind unquestionaby 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 shortestlat the equator
and increases with the latitude-at the
equinoxes-at about the same rate as that
at which the meridans decrease their dis
tance 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 below the
! horizon At the equator this time cannot,
| edges of the tropic zone II is about 81
minutes. a person with good cyesight 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 2S minutes after the sun
| has set without the aid of artificial light
and when there is no moonlight. This is
! the common sense experiment by which
the duration of practical twilight has been
/ determined The actual duration is con-
! sderably longer than the practical and.
| even at the equator, something like 20
minutes VIII relapse before night holds un-
| disputed sway. This is the length OF the
/ true. the astronomical, twilight.
| Il is at or near the equinOXe5 that the
| phenomenon under consideration is at its
shortest all over the globe. At those pc
riods il lasts at Honolulu 80 minutes, at
1 San Francisco 80. al London -, at St. Pc
/ tersburg 81. at the Arctic and Antartic cir
cies ~ and at the poles is days. When.
! then, we say that the poles have SIX
months light and six months darkness, it
| is little more than Il facon de parier The
| North Pole has no less than 222 days of
! practical daylight each year, the South
/ Pole 2I5 days and the equator l9T days.
| Nansen, when in high northern latitudes.
| was able to read the ''Verdensgang' many
| days before the lOnged- for sunrise follow
| ing the long winter night. The great
| length of the twilight in polar regions is
a boon indeed TO explorers. The popular
Imagination 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 Nan
/ sen. a Peary or a Jackson.
There is practically no difference in the
| length of the twilight at the equator at
| the equinoxes and solstices. Even at Hon
| olulu ii will not vary by more than a cou-
/ II IG,,t in, fln tyip lot
tudes the varying duration is very marked.
| In latitude 80 IL degrees, for instance, it
| lasts fifty-six minutes at the equinoXes.
| but at the summer solstice 1t lasts from
sunset to sunrise-that is to say, from
| $40 o'clock till $50. or for five hours and
| forty minutes.
North or south of SO degrees practical
twilight lasts all might at the equinoxes.
| The sun is. 1t is true. only twelve hours
above the horizon, but as he cannot get
| more than seven degrees below it there is
| continual daylight for the twenty-four
| hours In such cities as Stockholm and st.
| Petersburg there are close on TO fourteen
| hours of daylight at those seasons when
| day and night said to be equal. and at
the equator itself the day all the year round
is made up Of thirteen hours daylight aud
eleven hours darkness. 1t must also be
not forgotten that in those latitudes where
| the sun remains for months below the hor-
| izOn there is during that period good deal
of daylight so that along the eighteth
parallel north "a little. north of which
the Jackson Harmsworth expedition spent
| three consecutive years in the Franz Jo-
sef islands,, although the sun does not
rise between October 10 and February q,
| there is a 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 a few minutes up to some
hours without artificial light.
Missed Ideas.
(From the Louisville Times)
These Sunday school teachers get queer
answers TO questions sometimes. and the
| irreYerent Snickrr in their. sleeves when