The evening times., 1897-04-01
Changes in the Pictures Seen in
the Skies.
VENUS AS THE EVENING STAR
Jupiter and Mars VIII Also Shine
Conspfcuously- Moons Vary
ing Distance From the Earth.
Sun Dial and Mean Time-The
Position of the Planets.


She will be in apogee at p. M, on the
4th aud in perigee at p. m. on the 18th.
When the moon is nearest the earth, or In
perigee, she is % 1 g 4, and when reInotest,
or in apogee, 252,972 miles distant from
US, quite a considerable difference, which
shows the ecoentrieity OF the ortiit When
we say that the moons distance from tie
earth is 23S, $40 miles, the average dis
tance is meant, and this must be borne in
mind in regard to all the planets. The dis
tances of the planets from the earth must
necessarily vary much, as the planet in
question, if an inferior one, is at one time
between the earth and the sun, position
that is called inferior injunction; at
another time on the other side OF the sun,
a position known as superior conjunction
As 10 superior planets, the orbits of " nich
envelop that OF the earth, none, of course,
! can ever come between the earth and the
sun, but they may be either in conJunc ction
! and opposition. The moon, which re-
wolves about the earth, is sometimes be-
tween the earth and the sun, or in con-
junction, and III this position is new; at
other times on the other side OF the earth,
or ia opposition, and then it it is full.
The sun distance from the equator is
40 degrees, 40 minutes and % seconds
north on the first, and IA degrees, 56
minutes and - sec conds north on the
last, so that in course of the month it
passes through an arc OF 10 degrees, IL
uinutes. on April 10 the apparent and
mean times are alike. In these articles we
have called the readers attention several
times to the earth s motion around the sun
not being performed in i circle, but in
an ellipse. and that, in consequence of this,
and the inclination of the orbit to the
equator, apparent time is not and cannot
be uniform. To use such variable time
for civil and business purposes is wholly
impracticabe, and for this reason mean
solar time has universally been adopted,
which, -four times year, exactly agrees
with apparent or sundial time. The 18th
of April is one of those four dates, when
a correctly constructed sundial will indi-
cate the correct mean time. The difference
between apparent time and mean time is
called the equation of time, and is OF
very great Importance. The greatest dis
crepancy between these two times takes
place on November and February IL,
on which two DAYS the time indicated by
the sundial is respectively 6 minutes. 20
seconds fast, and 4 minutes, 80 seconds
slow of clock time. During the summer
the equation of time can never be greater
than 8 minutes.
The planet haercury viii leave the constel-
lation Pisces and enter that OF Aries about
the middle OF the month. BY the END Of
April IL will be on the boundary lines of
Pisces and Taurus. Venus Will linger in
Aries during the whole lengt OF the month,
and shine as an evening star with that
brilliancy that is peculiar TO her. She has
still a large eastern elongation, and willnot
set before a little after 8 O'Clock during
the earlier part OF the month. In bright
ness Jupiter certainly comes mex t To Venus,
and both these planets are unquestcnably
the two finest objects in the evening skies.
The great planet is stin in Leo, and will set
between 8 and O'Clock a. m. Nearly mid
way between Venus and Jupiter we easily
recognize the red-tinged planet Mars. Mars
at times is very brilliant then vieing with
Venus and Jupiter in luster. but at present
and for some time to come, though always
a very conspicuous object in the heavens, it
falls in brightness quite short Of them. 1tis
in Gemini. and will set soon after midnight
Not long after 8 O'Clock in the evening Sat
urnrises withthe constellat ton Scorpio, and
when during the summer months this fine
constellation occupies a higher position in
the heavens. Saturn will add very much TO
its intrinsic beauty. The planets Uranus
and Neptune have changed their positions
in scarcely sensible degree.
The reader, no doubt, necollects that the
earth is not a complete sphere, but what is
technically called An Oblate spheIoid, which
is a body generated by the rotation of an
eilipse about its smaller axis. The differ
ence between the equatorial and polar diam
eter is, it is true, comparatively small
quantity: twenty-six miles; in fact, small
enough TO render calculations based upon
the assumption Of the earth'S being er-
feet sphere in most cases sufficiently accu-I
rate but STILL it is sensible quantity
Since the force of attraction on objects on
the surface Of the earth depends upon the
distance from the center, where, for sci
entific reasons, into which it is not the
place here to enter, the force of attraction,
or gravity, mas be considered as ccncen-
trated, it stands to reason that objects can
not have the same weight on all points Of
the earth's surface. For instance, an OBJ
ject that weighs 100 pounds on the equator
would weigh 191 pounds on the poles.
This flattening at the poles of tie earth
or, as it is called, its oblateness, also causes
the linear length Of degree to be differ
ent in different degrees Of latitude. An
other name for oblateness is ellipncity,
which III ust not be confounded with eccen-
tricity, a term that refers to the distance
of either focus of an ellipse from it's center.
and which is always larger than the OBJ
lateness.
The determination of a planets oblate-
ness is a very delicate affair, and all at
tempts at obtaining reliable results have
thus far proved futile in the case of the
sun, moon, Mercury, Venus, the asteroids
and Neptune Saturn has the greatest
o6lateness of these that are known: then
come inorderof magnitude Uranus, Jupiter,
Mars and the earth, which is more nearly
spherical than the Others named
OF the conspicuous constell ellations, to
which in these articles we have confined
ourselves, that are on the meridian about
9 O'Clock in the April evenings we mention
Leo and Hydes. Leo, or the Lion, is a
noble constellation with The firstmagnirud
star Regulus, two second magnitude, six
third magnitude starsl and quite num-
Der of stars of inferior brightness The
westermost portion of this large constella
tion bears quite a striking resemblance TO
a sickle, by which nameit is often and not
inappropriately designated. Regulus, or
Alpha, is in the handle of this sickle This
star is the last in the list of first mag
nitude stars, in brightness somewhat infe-
Nor to Pallus, but superior TO Polaris. 1t
belongs TO the so-called nautical stars, OF
which we shall have sOrnethiup tn say