The Grange advance., 1874-07-15

comets observed up to the present time,
either with the naked eye or by means Of
telescopes, the majority are distinguished
by nebulosity surrounding the nucleus,
and great number, especially Of the most
brilliant ones, possess a luminous train OF
tail.
TIE DIVERSITY OF ASPECT
will perhaps some day enable astronomers
to class comets into genera, species and va
rieties, and will doubtless facilitate the
perfection of the theory Of phinomena
which these bodies present, and which is
still obscure. According to Professor
Spoor, of Rochester, comets are controlled
by the same specific law which govern
planets of the solar system. When in
their orbits thousands Of millions of miles
away from the sun they move very slow in
the arc of an ellipse almost immeasurable
The sun being positive and they deeply
negative, it begins to exert . controlling
influence over them as that attraction in
creases. continually in proportion as the
squares OF the distance decrease they move
swifter until as they approach the sun they
sometimes fly more than 500, 600 miles per
hour.
AT THEIR PER1HEL1ON
they are very near the sun, and become
highly positive, and hence are propelled
back again into fields of space with the
same lightning speed they were attracted
toward the great fountain of all motion.
The reason comets pass out of sight so
rapidly after passing their perihelion is
because they pass around the sun in orbits
much more elongated than that Of the
earth, and when they cross the plane OF
the orbit of the earth on their fight to re-
gions of space they are then moving in
one direction and the earth in another, and
as the earth moves at the rate Of $4,000
miles an hour and the comets at the rate
Of 10000 miles an hour, they seem to
move much faster, as they soon disappear,
while their motion is slower and slower
till they arrive at their aplelion point.
THE USE OF THE sPEcrRoscoPE.
Professor Chapman believes that there
was an attempt to use the spectroscope
upon Donati's comet, and the lines were
believed to indicate carbon. But the use
Of the instrument was not very well un-
derstood in those days. However, with
the experience We have since gained not
only in regard to the magnificent develop
ment Of the instrument itself, but also in
regard to the lines Of the various chemical
elements, we are in an immensely better
position for observations-that is, if the
comet shines by a light of its own. If it
merely reflects the light Of the sun we
shall get continuous spectrum without
lines at all.
VIEW OF PROF. EASTMAN, OF THE NATIONAL
OBSERVATORY.
Professor Eastman, Of the National OBJ
servatory, at Washington, D. c., being in
terviewed, vouchsafed the following in
formation:
The comet will reach it's perihelion in
its path nearest the sun, about the 9Th OF
July, but will be nearest the earth and
brightest about the Goth Of July. Its least
distance from the earth will be about that
Of Venus.'
suPERsT1T1ous ALARMS.
The reports about the disasters which
will occur should the comets tail come in
contact with the earth are purely sensa.
tional, since it is well known that stars as
small as the ninth magnitude have been
distinctly observed through the denses,
portion Of the nucleus of comets. No in.
tluence whatever on the weather, the cli-
mate or the health Of the inhabitants Of
our planet from comets has ever been de-
termined.
Next in the course Of the conversation
were the following questions and answers
"Can you give the distance of this
comet from the earth at the present time
and the speed at which he is travelling re.
duced to miles?"
Not exactly. We have not yet un'
dertaken the calculations required to de-
dermine these points, and you know tha'
in the progress Of comets toward the sun
their speed is so rapidly increased and t
such an astonishing velocity in turning the
sun that in determining their movement.
from day to day, nightly calculations arr
necessary. We take our observations nov
and make our calculations more deliber.
ately."
HARMLESS TAIL.
"You have no idea that the tail of thif
comet can possibly brush the earth or GU,
moon and cause thereby important a.
mOSnheric chanwos sP3