Delaware gazette and state journal. (Wilmington, Del.) 1883-1902, 1899-09-07
TIE Skies IN SEPTEMBER.

Il
on the 10th. last quarter on the Goth.
She will be in apogee on the 30th,
and in perigee on the 18th. Even the
most careless observer must have
noticed that the moon moves eastward
among the stars every night, perform
ing revolution from star to star in a
period of about 2714 days, called a
sidereal month. Since the SUMS east
ward motion among the stars is so
much slower than the moons, it is
evident that the moon from time to
time overtakes and passes the sun.
The phases of the moon depend upon
the relative position of the earth, moon
and sun, and the period from new
moon to new moon is called the
synodic month, which is nearly 21a
days longer than the sidereal, and con-
stitutes the ordinary month. When
the moon is nearest to the earth, or in
perigee, it is 81, 600 miles nearer to the
earth than when she is remotest from
the earth, or in apogee.
At the beginning of the month OF
September the sun is a little over
degrees distant from the equator, but
will reach it on the Esd, at half-past
O'Clock in the afternoon. at which
moment the summer season is at an end
and the autumn season begins. In the
almanacs the usual expression of this
transition from the summer to the au-
tumn season is 1.-THE sun enters Libra. !"
This is, however, not the constellation,
but the sign Libra. In consequence of
the procession of the equinoxes the
signs and consultations of the same
name are no longer identical, the con-
stellations having, so to speak, receded
by one constellation behind the signs
Of the same name. Tho division of the
zodiacal belt into IL consultations is
certainly very convenient one, but
1t must not be supposed that the width
of these consultations are exactly the
same. 1t would, in fact, be difficult
matter to define the line of demarca-
| tion, separating one constellation from
another, with geometrical accuracy.
| The sun at the moment of transition
| from the summer to the autumn season
will this year be in the constellation OF
Leo, instead of. as many might sup
pose, in that OF Virgo, which is the
preceding constellation of Libra, but it
will enter Virgo the next day after tho
beginning of the autumnal season.
There are. it is true, not few un-
solved problems in astronomy, but the
determination of the exact position of
| the sun, moon and the planets at any
day and hour of the year does not
belong to these, the astronomers being
able to fix these positions with such
accuracy as to elicit the amazement of
all persons that do not know the magi-
cal power of mathematics and the
nicely with which astronomical obser-
vations are made nowadays.
During the great portion OF the
F | ,,,n,,tl, Ma,orr,, rpi1I ha In Ian h1f
about the 9th will enter Virgo. Venus
will be in Leo, too, at first very close
to Regulus, the brightest star in that
constellation, but toward the end Of
the month will enter Virgo. At the
time of the autumnal equinox this
planet will be near the sun. Through
out the whole month it will not be
favorable for observation with the
naked eye. Mars is in Virgo. About
the middle of the month it will bt
near the bright star Spica in that con
stellation. We may get a glimpse o.
this planet soon after sunset, when il
will be lowering above the western
horizon until about o'clock. Jupiter
is very near tine boundary line of Virgo
and Libra, at first in tho former, anc
, at the termination of the month with
. in the latter constellation. The grea
planet will yet be acting as an evening
star and shine as such until nearly
o'clock. Saturn is in Sagittarius
close to the boundary line of that con
stellation and Scorpio. This plane
will set little before 10 O'Clock in tn
evening.
n 1t is, of course, plain to the reade
that the finding Of the longitude AMI
latitude Of places on the surface of tn
earth is of the highest possible i'm
portance, and as it is distinctly an as
/ Economical problem, it Is in place +
| say something about it in articles de
! voted to astronomical subjects. Their
, is number of more or less simple, in
genious and accurate methods of boil
finding tho latitude and longitude
There is not ship crossing the sea O
which both of these are not determine
a at least once day, and this is done b
. means of simple but indispensable
' instrument called seXtant. 1t is as
a tonishine what important results ca
: be obtained by means of this simpl
r. and portable instrument. Sir job
/ Herschel makes the noteworthy remar
il about it. that man with q little pol
v table instrument held in his hand an
Il applied to his eye, even with so III
h stable footing as the deck of a shiI
n shall say positively within five mile
4 where he is on boundless ocear
o This, he adds, cannot but appear
!. persons ignorant of physical astronom
a an approach to the miraculous. An
h yet the alternatives of life and deatt
v wealth and ruin are daily and hourl
q staked with perfect confidence on thes
: marvellous computations. One OF th
4 methods employed at sea Of finding til
i longitude of place is that by luna
\ distances. In the guide so indispen'
q able for the mariner-the Nautical A
Il manac = the distances of certain star
q called nautical stars from the moe
Is are recorded for every day in the ye;
/. and for every three hours each day fl
u the sake of ships going on long vo.
ages and cruises, computed for thrt
l. years ahead. These nautical stars al
+ all situated near the moons path, ar
IA their names are all familiar ones viz
l. Alpha, Arietis, Aldebaran, Pollux, R
\ gulus. Spica, Antares, Affair, Foma
II haut and Markab, all of which, excel
d the last, belong to zodiacal constelli
d tions, Markab, or Alpha Pegasi, belont
d ing to the constellation Pegasus. III
ii Nautical Almanac adds to these u
"a distance of the moon from the sun ar
10 the planets Venus, Mars, Jupiter ar
,e Saturn. The distances laid down
the almanac are computed as thong
In they had been observed from the cent
a. of the earth, but by mathematic
n PROCESS, called clearing of the lunar,
ne these almanac distances can be reduct
to those observed at any place. al
then the longitude can be determines
n. OF course, the usual method of fin
| ,pc, th,, l.,nrf I1Tla n