Griggs courier., 1894-08-31
THE TIME OF MooNRIsE.

THE TIME OF MooNRIsE.
u II E1fty.Ono Minutes Later ON Any Day
Than ON the Day Before.
The time of moonrise ON any day is
on the average about fifty-one minutes
later than on the preceding day. This
retardation is, however, by no means
constant in amount, being at times
very much less than the average and
at times very much greater. A very
marked diminution in the time Of re-
tardation occurs about the time of the
full moon which falls in September.
This moon is called the harvest moon.
The same phenomenon in less degree
occurs at the time of the next follow
ing full moon, which is known as the
hunters moon. The time of retarda-
tion during the harvest moon is less
than half an hour in our latitudes, in
instead of its average value of nearly
an hour, and for several successive
nights the moon seems to rise at nearly
the same time.
Briefly stated, the cause of the phe-
nomenon is this: At the time of the
rising of the harvest moon the ap-
parent path of the moon among the
stars is much less inclined to the hori-
zon than it is at other times, and the
ordinary days motion of the moon
along this path makes an unusually
small change of the position of the
moon with reference to its distance
from the horizon.
A more detailed explanation may
make the matter little more easily
understood. In addition to the ordi-
nary apparent daily motion which the
moon has in common with all other
heavenly bodies, it has another motion
by which it completes the circuit of the
heavens relatively to the sun once q
month, and the direction of this mo-
tion is generally not parallel with the
ing generally northward or southwark
as well as eastward. Anyone may see
this motion by an hours watching of
the relative positions of the moon and
star near it. The diurnal motion is al
ways on line at right angles to a line
drawn from the body to the celestial
pole, the point in the heavens approx
imately indicated by the pole star. It
is always perfectly uniform about the
pole as center, and it is this which we
take as our ordinary measure of time.
Now consider the position of the
moon and the sun at the time of full
moon. The moon rises just as the sun
sets. On the next evening at sunset
the moon will still be below the hori-
| zon, because it has moved eastward
among the stars relatively to the sun,
and it will not rise until the diurnal
motion of the heavens brings it above
the horizon. If the moons motion
were uniform and always along the
line of ordinary diurnal motion,
this retardiation of the time
of rising would always be the
same. and would, as stated at
the outset, be fifty-one minutes per
day. But at the time of harvest moon
the direction of motion of the moon
among the stars is considerably north
! ward as well as eastward, and at the
time of moonrise this line makes COM
paratively small angle with the hori-
zon, very much less than it does at
other times of full moon during the
year. Therefore, at sunset ON the day
after the full, the moon having moved
along line which is inclined to the
horizon at a much smaller angle than
usual, its distance below the horizon
will be less than the average, and
hence a smaller amount of diurnal mo-
tion will bring it into view-that is,
the retardation of time of rising is less
than it is at other times. This condi-
ton continues for several days.
Several other things, notably the in
clination of the moons orbit to that of
the earth, and the varying rate of mo-
tion in the orbit due to variation of dis
tance from the earth, tend to change
the amount of daily retardation, but
they do not depend on the time of the
year, and they sometimes intensity and
sometimes diminish the peculiar phe-
nomenon of harvest moon. Latitude
has strong effect, and in northern
Europe the phenomenon is a much
more noticeable one than it is in the
United. States. In fact, if one goes far
enough north, the harvest moon may
rise even earlier on any night than it
did on the night preceding.-N. Y. Sun.
How Shrimps Are Caught.
The shrimp sold in the city are
caught during the night, before by
casters" who 60, two in a boat, to
some favored locality and there ''cast"
all night long for the delicious little
crustacean that is served up at nearly
every hreakfasf table in the cifu In, tho