Atlanta semi-weekly journal. (Atlanta, Ga.) 1898-1920, 1910-02-22
BY OTIS AsHMoRE.


Now that Halley's comet is rapidly
approaching the earth. and is soon to be-
come an object of great popular interest,
the public will desire to know the leading
facts concerning this famous celestial
visitor, and to learn something OF It's
eventful history. In just what part or
the heavens ii is at present. when and
where it may be seen best, when IL Will
| be nearest the earth, and what danger, Il
/ any, is there of collision with our globe,
are some of the questions that are nat
| uralIy asked.
The comet is at present in the constelia-
ton Pisces. about half way from the
zenith down to the western horizon at
dark, and about eight degrees west OF the
| pIanet Saturn. II is not yet visible to
the naked eye, and as il is approaching
the sun it will soon be lost in his rays
till about April /, when IL will reappear IN
the morning sky ahead of the sun. On
March "A it will be on the opposite side
of the sun from us, and on April 20 1t Will
pass its perihelion at a distance of $1,000
600 miles from the sun.
SEEN IN MORNING.
From that time till May Is it will be. a
glorious spectacle in the morning heavens.
On May Is it will pass directly between
the earth and the sun, when 1t VIII be
only Il 600, 900 miles from us. As II sweeps
| rapidly nv us il will pass from the morn
ing to the evening sky again, and after
a few weeks it will bid US adieu for its
long tourney into the depths of space, not
70 return to US again in three-fourths of
a century.
Asit rushes by us on May is it will pass
directly over the disc of the sun, and a
6ne opportunity will be afforded to tesy
by observation the size and character of
the nucleus III ii consists of solid par
ticles of considerable size, or OF dense
aggregation, it will be projected as dark
mass against the bright face OF the sun,
but if il Is composed of gas only. or OF
very small particles widely diffused. 1t
will pass across the sun as an invisible
mass. II is not improbable that the earth
at that time may become involved in tn"
/ nebuIosity of its tail, but the matter COM
posing the tail is so extremely tenuous
| that the earth will in all probability pass
through it without any sensible effect.
The transit of the comet across the face
| of the sun will take place during the
night on the western hemisphere, and
hence we could not see II any way, but
astronomers on the opposite side of the
earth will doubtless observe this phenome-
non with great care.
The orbit OF Halleys comet is very
elongated ellipse. extending out into space
/ zoo 100000 miles beyond the orbit of Nep-
tune AT it's perihelion it's distance from
1 the sun is 54.OO0,O00 miles, or somewhat
less than the distance of the planet
/ Venus. II makes a revolution around the
| sun i'm about 10 years. though owing to
the disturbing effect of the larger planets
| on its motion. this period may vary one
| or two years. Its motion in its orbit is
retrograde; that is. IL moves around the
4 Of
the planets Its orbit is inclined about
Is degrees to the plane of the earth
orbit, and these two orbits are so related
that a collision between the earth and
the comet is impossible.
| GASEOUS MATTERS.
There is much uncertainty about the
composition of cometary masses, but the
| spectroscope shows that the head is
| composed OF gaseous matter involving
| probably masses of solid matter closely
| grouped together. The tail consists OF
gas, chiefly hydrogen, in a state of eX-
treme tenuity. The fact that the tail is
! always turned from the sun has led TO
the theory that the matter of which Ii is
composed is driven off from the head by
some repulsive force of the sun. Sew
eral ingenious theories have been ad-
vanced to account for the phenomena Of
comets tails, but none Of them are alto
gether satisfactory. The head of a comet
generally possesses some self luminosity,
I but the tail owes its light to solar re-
Election.
The possibilities of a collision of the
earth and comet, and the probable re-
suits of such an occurrence, have often
been discussed. but owing to our ig-
norance of cometary masses, such dis
cussions are little better than specula-
tions That such a collision is possible
no one will deny. but the probability OF
il is extremely remote. If comet OF
small size and density should run full
tilt against the earth, our atmosphere