Delaware gazette and state journal. (Wilmington, Del.) 1883-1902, 1902-07-10
THE SKIES in July.

In the course OF the month OF July
the moon will be new on the 18th, in
her first quarter on the 18th, full on
the Goth and in her last quarter on the
2sth. On the 4th she was nearest to and
on the 10th will be remotest from the
earth. While at the beginning of the
month the sun is still near the summer
solstice, he will have descended nearly
5 degrees at its termination. In course
of the month the rising and setting
points Of the sun will shift 7 degrees
along the horison toward the true east
and west points of the same.
The planet Mercury will remain in
Gemini throughout the whole month.
On the 18th it will reach its greatest
elongation west, being then 20 degrees,
30 minutes distant from the sun. The
reader will remember that this swiftest
of all planets, making q circuit round
the sun within the brief period of three
months, and whose synodic period is
about one month longer, not infre-
quently passes within month through
three consecutive zodiacsl constella-
tions. That during july it will linger
in one constellation only may prove
somewhat perplexing to some, but it
must not be forgotten that the apparent
motion OF the planets renders the
whole matter plain. Viewed from the
sun or distant point on the line
drawn through the sun perpendicular
to the plane Of the .ecliptic, the planets
would be seen to travel in their nearly
circular orbits with a regular motion
but as seen from the earth the apparent
motion is much more complicated, be-
ing made up of their actual motion
around the sun combined with an APP
parent motion due to the earth's own
movement. The apparent motion of a
planet as seen from the earth is called
geocentric motion, and this geocentric
motion is made up of two motions
that Of body moving once a year
around the circumference of circle
equal to the earth S orbit while the
centre of this circle itself goes around
the sun upon the real orbit of the
planet, and with periodic time equal
to that OF the planet. In consequence
of this Hoped" motion we have the
peculiar back-and- forth movement of
the planets among the stars. 1t plainly
follows from this that by this retro
grade motion Of planet it will often
finger in the zodiacal constellation in
which it happens to be at the time
longer than when its apparent motion
is direct. The very irregularity of these
apparent planetary motions suggested
to the ancients the name of planet, a
Greek word signifying. wanderer.
Venus and Mars will be in Taurus
during the greater portion of the
month, but toward the end will enter
Gemini. They will be near together
throughout the whole month, and on
the last day they will be but little
more than degree distant from each
other, thus presenting the ever attract
i've phenomenon Of planetary con-
junction. Both will rise between and
o'clock and act as morning stars.
Jupiter and Saturn have not materially
changed their position since last month,
the former being in Capricorn and ris-
| ing about 8 o'clock in the evening, the
latter being in Sagittarius and rising
about an hour earlier.
The subject of the atmosphere sur
rounding the earth is distinctly an
astronomical one of the highest possible
| Importance and interest. The atmos-
| phere is one of the three divisions that
compose the structure of the earth.
That part of the earth which forms the
dry land and is a vast strong ball is
the atmosphere. the liquid layer resting
in the hollows of the atmosphere is a
water shell, called the hydrosphere, and
that envelope Of gas surrounding the
whole to considerable height is known
as the atmosphere. 1t was not until
the close. of the Eighteenth Century
that the air ceased to be regarded as
an element BY experiments it was
then found that the atmosphere con-
sists of two gases-nitrogen and oxygen
but it was not discovered before the
year 1894 that it contains still more
inert gas than nitrogen, which is called
argon. This forms one hundredth oi
the volume OF air from which oxygen
is removed. Besides these the atmos
phere contains carbonic acid and water
vapor, both Of which play very con.
spicuous part in the economy of nature.
There is, however, another ingredient
of the atmosphere solid dust-the i'm.
portance of which was not recognized
until comparatively recent date.
Solid dust is always present in the at
mosphere throughout ITS whole depth.
Twenty million meteorites are calcu
lated to reach the earth every day anc
most of these are broken up by the
friction of the air, furnishing a supply
of cosmic dust, which, being exceed
ingly fine and even invisible, settles
down very slowly. Terrestrial dust i.
carried into the atmosphere by ascend
ing currents of air and is of many
kinds, resulting from the wearing dowr
of rocks. from volcanic explosion, from
flowers in the form of pollen, from
minute organisms, either plants OF
animals, from burning fuel, from fac
tories, mines, -four mills and from tn,
spray Of the sea, The number of mote.
is almost Incredible. Every puff O
smoke from a cigar contains abou
4,OO0, 600, 900 separate granules of dust
Dust appears to float in the atmospher,
and the notes of a sunbeam seems Il
be rising as often as falling. This is
h owever, result of currents of air. Ii
still air dust always falls, but the larg
notes fall most rapidly under the pull
of gravitation and against the resist
ance of the friction of the air. Ii
, one cubic centimeter of the air of grea
cities there are hundreds Of thousand
: of notes; in the air of small village
there are thousands, and there ar
hundreds even in the open country ia
from towns and factories. These minut
notes catching and scattering the sun
light are the agents by which the who'll
atmosphere is SO illuminated that no
: even the brightest of the stars o
planets is visible by day. If the al
were free from dust we should plainl
see the sun shining from a perfectl
black STARTLED sky, and one side of
house would be dszzlingly illuminated
the other in shadow of absolute dark
ness.
The blue color of the sky is largel
r due to the scattering of sunlight b
the dust notes of the higher layers, /
| "a ha =