Shenandoah herald. [volume] (Woodstock, Va.) 1865-1974, 1874-09-24
HOW EcLIpsEs OCCUR.

have said that the sun pursues a
certain definite path among the stars
about half a degree wide, which you
could see if he left any trace there; so
also, if you could mark its position Of
the moon to night among the stars, and
mark its position at every hour during
her whole course, you would find that
she also has pursued a definite path
among the stars, but you would not find
this path to be the same as the suns
path. If it were the, same, we should
have an eclipse Of the sun every time
the moon crossed the sun, and passed
on the other side of the earth from the
SUM- But the two paths are inclined to
each other about SO. They cross each
other at point which, in the month of
October 1874, is very near the sun.
The moons path is south of the suns
in nearly all that part of the heavens
which we can see in the evening of
that month but it approaches the sun 3
path, and crosses it near the eastern
horizon, and in most of the invisible
half OF the sphere, or that part, below
the horizon, the moons path is farther
north. All this will be clear on exam
lnlng the star maps, where the dotted
line shows the path of the moon during
1874, crossing the suns path in the
consultations Aries and Libra.
These two opposite points in which
the moons path crosses the path of the
sun are called the nodes. It is very
clear that unless the sun is near one of
the moons nodes when the moon
herself passes by, tho moon will pass
above or below the sun, according as
her path is above or below that of the
sun at this point, and consequently
there will be no eclipse. But if the
snn happens to be near the node, then
the moon will necessarily pass over bis
face and eclipse some portion of him.
Now, as l have just explained, there
are too opposite nodes; the one set a
few hours ago, and the other has just
risen. Since the sun makes the whole
circuit Of the heavens in the course of a
year, he crosses the moons nodes twice
in that time. In 1874 he crossed
one node in May, ard will cross tie
other node in November; consequently
it is only about these two tissss that
any eclipse can take place
year.
If the moon always followed the
same path in the heavens, we could
never have any eclipses but at those
two seasons. But if we watch the mo-
tions of the moon for several years in
succession, we shall find that her path
is continually changing. At the pres
ent time she passes seven degrees north
of Aldebaran month hence she will
seem to pass the star at almost exactly
the same distance but ifyou continue
your observations for four or five
months, you will find that she passes it
perceptibly farther north, and in three
years you will End that she crosses it at
the distance of about ten degrees AT
ter that she will begin to cross farther
south, passing nearer Aldebaraa at
every revolution for eight years, until
in 1858 and 1886 she will pass right
over it. If the moons path were paint
ed on the heavens, you would see that
every time the moon came round to the
same point in her path, which takes
place about every twenty seven days,
she would cross the suns path about
three of her own diamcters sooner than
the month before. In the course of a
year, therefore, she will have crossed
about thirty>six diameters sooner, or
farther to the west. In the course of
twenty years you will find that this
motion has been kept up until she
crosses at the same point she does now,
and thus the nodes have made COM
plete circuit Of the heavens. The sea-
sons of eclipses vary. therefore, in the
same manner. This year they are in
May and October; in FIVE years from
now they will occur three months earl
Ter, and we shall have them in February
and August; five years more, and they
will be in October and May; five years
more, in August and February FIVE
years more and they will correspond
once more to what they are now
From ''Some Talks of an Astronomer
by Prof Simon Newcomb, in HGrpers
Magazine for October.
A lady prayed for her daughter
thirty-nlne years without receiving any