Ellsworth American. [volume] (Ellsworth, Me.) 1855-current, 1910-10-19
THE HARVEST MOON.

Why II Rises 1t Nearly the Same
Time Several Nights.
The early evening skies ct this time Of
the year are probably more interesting
than at any other season, writes Prof. g.
Alfred Mitchell, Of Columbia university.
Those who watch the rising OF the moon
in these fall months cannot fail to notice
the difference which years and years ago
caused the pious farmer to thank the all
wise Creator for causing the full moon to
rise ct nearly the same time for several
nights in succession, thus giving sddi-
tioDal light for harvesting the crops.
The "harvest moon" is the full moon
which falls nearest the autumnal equinox,
and in 1910, occurred on Sept. IS. The
"hunter's NOON comes on Oct. Is.
1t is surprising that so few people know
the exact cause of these peculiarities of
the moon, but little thought will readily
explain them. As every one knows, the
moon is moving eastward in her orbit
round the earth, and consequently rises
later each night. On the average this
amounts to about fifty minutes. BY con-
sulting any almanac, however, it will be
seen at Q glance that the moon does not
rise each night fifty minutes later, but
that the intervals between successive
nights vary enormously at different times
OF the month.
The moon revolves about the earth
nearly in the plane Of the ecliptic; also,
the time Of her revolution is month, and
M nd
through her variation of rising and setting,
as can be seen by consulting the almanac.
In each month there is a least variation
in the time Of moonrise, but only in the
autumn months does this come near the
time Of full moon. As we ordinarily
notice the time of the rising Of the moon
only when it is near the full-when it
rises at sunset-the "harvest noon, be-
fore the days OF congested rural life and
electric lights, came to be marked
phenomenon.
But not only do the "harvest" and
"hunter's" moons rise at nearly the same
hours for several nights, but they rise
farther and farther north of east. The
reasons may be vizualized with great
readiness by getting hollow rubber
ball three inches in diameter and sticking
a knitting needle through it. Mark on it
two circles, one halfway between the
points where the needle pierces the ball,
which we will call the equator. Now
make the second circle run completely
around the ball and inclined to the first
by 22h degrees. This will represent the
ecliptic, the path OF the sun and the ap-
proximate path Of the moon. The two
circles intersect in two points, the
equinoxes.
Represent the position of the moon each
night by marking of points on the ecliptic
five-eighths OF an inch apart, beginning at
one of the equiuoxes. Immerse the ball
in pail Of water with the knitting needle
pointing north. The surface of the water
will represent the horizon. The angle be-
tween the needle and water should be the
latitude Of the place Of observation.
Twill the ball about the knitting needle
by means Of the fingers, making the ball
move from east to west, and we have there
represented the revolving heavens. The
sun and moon both move along the ecliptic
from west to east and going in this direc-
ton around the circle, the point where
the ecliptic goes below the equator marks
the autumnal equinox.
Revolve the ball slowly and notice the
varying angle which the ecliptic makes
with the surface of the water, paying par
ticular attention to the east side Of the
ball. II the autumnal equinox is in the
eastern horizon, it is seen that the ecliptic
is inclined at but small angle to the hori-
zon, and that it requires but very small
turn Of the ball to bring the moon in its
several positions near the equinox, sue
cessively above the horizon.
This will explain clearly shy the moons
near the full in September and October
rise at nearly the same time, and why