The evening times., 1899-07-01

2Sd in perigee.
Since the 2lst of June the sun has been
slowly moving southwark. Today it Will
and on the last OF the month a little over
is degrees l6 minutes and "a seconds north
of the equator. tiaversing during the month
an arc of a little over 5 degrees. The exact
position OF the sun north and south OF the
equator, or, to use a technical term, its
declination, enters into so many astronom-
ical computations and is of so great an i'm
portance that the Nautical Almanac"
gives it for every day in the year with a
correction for every hour. The problem
involving the calculation of the suns rising
and setting, consequently the length of the
days and nights, of the points of the suns
rising and setting on the horizon, of the
time when the sun will begin and cease
10 shine on the north and south walls of
buildings, of the length of twilight. all of
these and many more requires knowledge
of the declination, and il becomes, there
fore, of great Importance TO compute ii
with great accuracy, and to lay down the
results in that book so Indispensable TO the
mariner and the almanac makers-the
under the direction of the professors of the
United States Navy. For many years tEis
important work has been directed by that
fine mathematician and astronomer, Prof.
Simon Newcomb, 10 whom the great per-
fection of the American Nautical Al
manac" is chiefly due.
While Mercury Will be in Gemini at the
beginning of the month, it will be in Leo
at its end. Venus Will at first be at Tau
ID
3 and o'clock in the morning, she will
shine as morning star and be visible for
scme time even after the morning twilight
has considerably advanced. Mars is still
in Leo. At the beginning of the month
this planet Will set about half-past 10 in
the evening. and towards its termination
an hour sooner AS soon as the first mag
nitude stars become visible Mars may be
seen little less than midway between the
meridian and the Western horizon, con-
spicrcus by its intense redness. Jupiter
is sJiil lingering in Virgo. quite close to
Spica, the most conspicuous star in that
constellation. This beautiful planet will
be visible as evening star until about mid
night. Saturn is in Sagittarius and not
very far from a portion Of Ophiuchus,
constellation to be described farther on
This planet viii be on the meridian at
about o'clock Uranus is in Scorp:o and
Neptune in Taurus. but ON account of their
immense distance they are not visible TO
the naked eye, though a very keen eye
may catch a glimpse of Uranus on cloud
less and moonlsss night.
Ire correlation Of sciences has become
especially manifest in the case OF astron-
omy, the aston shng achiev ments Of which
within this century are principally due tc
the marvellous discoveries in the physical
and chemical sciences, The greater perfec-
uon of mathematical methods. and the ap-
plica;icn Of the principles Of analytical me-
chanics. all OF which have lent their pow
erful aid in making astronomy one of the
most perfect in the whole array of sciences.
Photography, especially. has been of in
estlmab bic benefit for astronomical obser-
yations and produced results that might
not have been found by any other method
Prof. Pickering OF Harvard University
has been one of those who paid much at
tenticn 10 observations by means OF pho
Biography, especially in observations of the
eclipses OF the satellites of Jupiter Pho
Biography has been extensively applied to
observations of the moon. the nebular. the
solar corona, the solar spots, and the tran
sit OF Venus. In making charts of the
stars, which for many purposes are more
convenient than mere catalogues, photog-
raphy has played, and is destined to play.
a still greater part. Quite recently very
satisfactory results have been obtained by
the aid of photography in determining the
annual parallaX of stars.
On the 14th of August, 1888, a new
planet was discovered by means of pho
tCgTaphy at the Urania Observatory, in
Berlin. by Herr C. Witt. The same night
il was also caught on a Photographic
plate by Charlois, of Nice but does not
seem to have been detected on the plate
until after the announcement of Wits
discovery. The newly discovered planet
was for some time Professionally designated
as D. @, but is now called Eros. 1t
was so faint as easily 10 escape notice
and since its first discovery has Deen
detected on at least twenty or thirty plates
made at Cambridge United States and
other places before Witt found it. The &c
centricity of the orbit of Eros is eXtraordi-
narly large, in consequence of which there
is great difference between its maximum
and minimum distances from the sun. Its
aphelion distance is 1G6.305 eco miles and
its perihelion distance 104. sol 600 miles,
making its average distance 135, ,433, coo
miles, while the average distance of Mars
is l4l 500 600 miles so that about half of
the orbit Of Eros is within that OF Mars.
1t would not be proper to say, as oeca-
sionally it has been said that the path of
Eros lies within that of Mars. The &C.
centricity of the orbit is so considerable
as 10 make the planet approach within
fourteen millions of miles of our own path
around the sun. The synodic period of
Eros-that is, the period between two
consecutive conjunctions or oppCsitions-
is $40 days, even exceeding by thirty days
that of Mars, which, before the discovery
of Eros, enjoyed the distinction of having
the longest synodic period of all the plan
cts. The most favorable position for OBJ
seryation which superior Planet can
have is when opposition occurs near its
perihelion, since in this position the
planet is nearest to us. In the case of
Eros this must have been in 1894, when
its stellar magnitude was about the sew
enth, or almost within naked-eye visi-
bility. This will again happen in 1924
and in that year astronomers will be en-
abled to provide more accurate value of
the suns distance than has been obtained
by any other method. Eros Will then
come within 4,000,G60 miles nearer the
earth than Mars ever does and thus pre-
sent most favorable position for obser-
walton. The sidereal period of Eros, with
in which il makes cne complete revolu-
ton around the sun. is 642.93 days thus
being by about A days shorter than that
of Mars. Though the size of Eros has
not been accurately determined it is in all
probability not exceeding twenty miles In
diameter.
The principal consultations that will
come 10 the meridian at about 9 o'clock
I'm the July evenings are Scorpio, Hercu-
les. and Ophiuchus. OF all the twelve con-
stellations of the zodiac Scorpio is indis-
putably the most brilliant. The peculiar
configuration of its more prominent stars
is an unmistakable resemblance to a boys
kite with long tail. The principal star
is Antares, of the first magnitude, and in
its intense redness resembles the planet