The Wilmington daily Republican. (Wilmington, Del.) 1890-1902, 1894-02-22
HARvts, AM HUNTERS MOONS.
Brief Statements as to the Causes of These
Celestial Phenomena.

The time of mOonrise on any day IL on
the average about 81 minutes later than
1t was on the preceding day. This retarda
ton 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 retardatiun occurs about the
time of the full moon which falls in Sep.
TENDER. This moon Is called the harvest
moon. The same phenomenon in less
degree occurs at the time of the next fol
loving fall moon, : hich il known as the
hunters moon. lie time OF retardHtion
during the harvest moon is less than half
an hour i'll our ATTITUDES, instead of its av.
erage value of nearly an hour, and for sey
eral successive nights the moon seems Ia
rise ut nearly the same time
Briefly stated, the cause of the phcnom,
cnon is this At the time of the rising 81
the harvest moon the apparent path OF
the moon among the stars is much less in.
Clined to the horizon than il il at other
times, and the ordinary dizzy = motion OF
the moon along this path makes an nm.
usually small change Of position az Tho
moon with reference to its distance from
tho horizon.
A more detailed explanation may make
the matter little more easily understood
In addition to the ordinary apparent daily
motion which the moon has in common
with all other heavenly bodies, it ha,
another motion by which it completes Ill,
circuit of the heavens relatively TO the SUI
once a month, and the direction Of thi'
motion is generally not parallel with til,
direction of the diurnal notion it beinl
generally northward or southwark as wei
as eastward. Any one may see this mo
tion by an hours watching of the relativ,
positions OF the moon and star near il
J The diurnal motion is always on line n
+, right angles TO a line drawn from the hody
10 the celestial pole, the point in the heav
ems approximately indicated by the pol
star. 1t IL always perfectly uniform abou
the pole as a center, and it is this which
1 we take as our ordinary measure of time.
! Now consider the position Of the moor
I and the sun at the time Of full moon. Tn
j moon rises just M the sun sets. On TIN
next evening at sunset the moon will still
be below the horizon, because it has move,
eastward among the stars relatively to tn
sun, and it will not rise until the diurna
motion of the heavens brings it above tn
horizon. II the moon s motion were I'm
/ form and always along the limo of ordi
J nary diurnal motion, this retardation O
the time of rising would always be tn
I same, and would, as stated at the outset
! be 81 minutes per day. But Mt the tim
of harvest moon the direction of motion O
I the moon among the stars is considera bl
! nurthward as well as east ward, and Mt tn
| time of moonrse this line makes a com
| paratively small angle with the horizon
!, very much less than it does at other time
of full moon during the year Therefore
I at sunset on the day after the full, tn
moon having moved along line which i
), inclined To the horizon at n much smalle
angle than usual, its distance below til
horizon will Ire less than the average, am
hence smaller amount of dinrnal motiu
will bring it into vicw-that Is, the retaI
: dation of time of rising il less than it
:. at other times. This condition continue
/, for several days.
\ Several other things, notably the incl
/ nation of the moons orbit to that of til
earth, and the varying rate of motion
n the orbit due to variation of distance fror
3, the earth, tend to change the amount [
daily retardation, but they do not Deepen
on the time of the year, and they sometime
Al intensity and sometimes diminish the p,
culinr phenomenon of harvest moon. lat
itude has a strong effect and in norther
I Europe the phenomenon is n much MOI
noticeable one than it is in tho Unite
states. In fact, If one goes far enoug
north, the harvest moon may rise even cal
lier on any night than il did ON the nigh
+ preceding. Popular Science Monthly.