Delaware gazette and state journal. (Wilmington, Del.) 1883-1902, 1900-08-09
THB SKIES IN AUGUST.



moon will present tho following phases;
First quarter on the Sd, full on the
10th, last quarter on the 18th and new
on the oath. On tho 18th she will be
in Lerigee and on tho 9th in apogee
The sun, in the course Of the month,
will traverse an arc of nearly 10 de.
grees north declination and be about
81 degrees distant from the equator at
the end of the month. On tie last day
she will rise and set little over ii dc.
gtees north of the line east and west
points of the horizon Of Baltimore.
The planet Mercury during the
greater portion of the month OF August
will be in the constellation Cancer, but
toward the last in Leo. Venus through.
out the whole month will be in Gemini
and shine rs morning star. She will
rise between ? and 3 O'Clock 10 the
morning. We have once or twice men,
toned before that Venus Is at her max
imum brightness neither when she is
inferior nor in superior conjunction,
since 10 the former position too small a
portion of her disk is visible, and IN
the latter position, though full, she sub.
tends too small an angle. She assumes
her greatest brillianoe when her elonga-
tion is about 40 degrees IL, about
36 days before and after inferior con-
junction. In this favorable position
she will be on the 14th of the month,
and she will emit then such brilliant
light as TO make it worth ones while
to rise early in the morning and to have
look at her. At the period Of her
maximum brightness her light is so in
tense as to make objects illumined by
her cast perceptible shadows. The
planet Mars. too, acts AZ morning
star. 1t is ut present on the boundary
line mat separates the constellation
Taurus and Gemipi and rises little
EAST O'Clock. The great planet Jupi-
ter is at present the evening star par
excellence. Still lingering In the sum-
ner constellation Soorpio, this beauti-
full planet will be visible until about
half past 10 o CLOCK in tho evening and
unquestionably forms the most beauti-
iul 6pIeci in Lhe evening skies. East
Of Jupiter, in the constellation Sagit-
tarius and near OEhiuchus the planet
Saturn will not fail to arrest the OBJ
servers attention, enhancing by his
presence the beauty of that portion of
the sky. saturn sets about an hour
after his biother planet Jupiter.
Uranus is also in Scorpio, so that the
threN great planets Uranus. Jupiter
and Saturn-are near together, though
the great distance of the first of these
renders it very faint object for the
unaided eye. Not far from Venus, also
in the constellation Gemini, is the
planet Neptune, though visible only
through telescope. Some of the
readers may recoilect the transits of
| Venus across the sun S disk in the years
1874 and 1882, which were predicted
long before the phenomenon, occurred.
and it has been calculated that the hext
two will occur in the month Of June in
the years 2OOi and 2Ol2, none happen
ing in the twentieth century. 1t may,
therefore, be presumed that after the
certainty with which such predictions
are invariably horne out by facts there
is scarcely person incredulous enough
to dcuht The accuracy OF such astron-
omonical predictions based upon i'm
mutable mathematical laws and not
mere speculation. Now the question
may arise in many one's mind, wha.
is necessary to render prediction as to
certain planetary positions possible?
This question is easily answered. In
order to lind planet place either in
the past or in the future at any given
time it is necessary to determine the
planets path around the sun or its
orbit with the utmost exaotness. This
has been done with all the PLANETS thus
far known. 1t cannot hut be OF great
interest for the reader to know certain
quantities that must be given in order
to describe the orbit with precision,
these quantities being known by the
name of the element OF planets
orbit, an expression which many of
the readers cannot fai to have heard
often, esnecially in connection with
comets There are seven OF these Gle.
ments and we shall mention them In
the order IN which they are generally
given. 1t may be presumed that nearly
everybody knows that the planets do
not move In circles around the sun
though some orbits verge closely upon
circles, but in an oval closed curve called
ellipse, and this ellipse is perfectly de-
termined by the semi major axis, which
Is half its maximum diameter, and the
eccenti lefty, which is the ratio of the
distance OF the focus from the centre
OF the ellipss to the semi.major axis.
These are the first two elements. The
third is the inclination OF the plane OF
the planets orbit to the plane OF the
eaIth 8 orbit. the eoliptio. The four tn
is what is called the longitude of the
ascending node and is the angle which
the straight line that connects the sun
with the yerna' equinox in the plane OF
the ecliptic makes with the straight
line that connects the sun with the as
cending node in the plane OF the
planets orbit. The fifth is what is
technically called the longitude Of peri
helion and is simply the direction in
which the major axis of the elipse lies
on the plane of the planets orbit. The
last two are the periodic time and the
epoch, the former being the period Of
revolution of the planet about the sun
and the latter the longitude Of the
rlanet as seen from the sun at some
given date, usually January LIST, 1850,
or l9o0, or else some precise data al
which the planet passed the perihelion
or the node. How these different clio.
ments are determined is, OF course. the
specihc business of the professional as
tronomer, and any explanation of the
process would be entirely out OF place
here, hut it certainly ia useful to know
what these elements arc. A question :
very pertinent one--here obtI udes
inuii uPon VIE iniuu, VIZ, wnether the
planets do mot disturb each other in
snch degree as to change their ellip.
ideal motion around the sun? The sinh
leot OF planetary perturbation, as these
mutual disturbances arc called, is in
ninsically very interesting ope and
certainly merits few remarks, Tbe
central body that attracts all ths
planets and causes them to .revolre
around it is the sum- and in regard n
the above guess ion of mutual perturba
ton eyerythinp depands -, m 800 -. -