Alexandria daily gazette, commercial & political. [volume] (Alexandria [Va.]) 1808-1812, 1811-09-28
C O ME- r S.

The following observations on COMETS,
are extracted from a London Magazine pub
lisbed in November, 1907 - s.
A COMET, yulgarly called a blazing star,
/. ON account ofits appearance, is very extra
ordinary sight; for though the number Oh
them be great, yet, on account OF the long
period of their revolution, they but very sell
dom appear They are supposed to consist OF
a very compact and durable substance, caPa-
BILE of the greatest degree OF heat and cold
without being subject to dissolution, and, like
the planets shining only by reflection.
By the ancients, Comets were considered as
yanors. or meteors and of this opinion was
Aristotle. the celebrated Greek Philosopher.
These pbenomena's were therefore treated
with neplect, until the time of Seneca, who
observed two very remarkable ones, which he
scrubbed not to place amongst the celestial
bodies, though he owns their motions to be
governed by laws not then known.
DR.. HALEY declares, that notwithstanding
all his researches inp the histories OF Comets,
he found nothing satisfactory; until a Con-
staatinopolitan historian and astronomer, in
the year A. D. 1887, pretty accurately de-
scribed the paths of a Comet amongst the fix-
ed stars. The next Comet which appeared,
was in the year l472, and was observed by
yReeiomantanus il was the swiftest OF any
that have hitherto appeared, and the nearest
to the earth. This Comet so dreaded on &C
count of the magnitude of its body and tai,
moved at the rate of 40 degrees ola great cir
Gle in the heavens, in the space OF one day,
and was the first of which we have any pro-
per observations. In the year 1877, re-
markable Comet visited this earth, to the STU
div of which Tycho Brahe sedulously applied
himself. This great astronomer, after many
faithful observations, found that 1t had no per-
ceptible diurnal parallax; and consequently
could not be an AERIAL vapor. Tycho was sue
ceeded by the sagacious Kepler, who DISCO
yered the true physical system OF this world.
AT length came the prodigious Comet OF
1850, which descended almost perpendlcu-
larlv towards the sun, arose from him again
with equal velocity, and was seen for tour
months together. Not long after, the IL
mstrious Newton demonstrated not only what
Kenler had found did necessarily obtain in the
planetary system, but also that Comets OBJ
serve the same law, moving III very long e.
cI;nses round the sun, and describing equal
areas in equal times.
The revolutions ofonly two Comets Cor the
number of wears necessary for performing
iourney round the sun) are known with
anv certainty. The one is that which appear
ed in the wears 1856, 1881, 1907, 1882 and
l75e, and is ascertained to move round the
sun in 76 years it will therefore make Its
appearance in 1885. The other is the Comet
seen in 1880, in llo6, In s3l, and soon alter
the death of Julius Cesar, about forty tour
years before Christ. 1t is mentioned by ma
nv historians Of those times, and by Pliny In
his, natural history, where Augustus Caesar
saws concerning it," In the very days of our
panes, hairy star (Sydus Crini;um) was
Seen for 7 days in that part of the heavens
which is under the Septentriones it arose
about the eleventh hour of the day, and was
clearly to be seen all over the world."-Ihe
period of this Comet is therefore ascertalned
to be about FIVE hundred and seventy FIVE years
old. It's next appearance will be III the year
2255.
The number of Comets belonging to our
system is unknown, but it has been ascertain
ed. that more than four hundred and fifty have
been seen, but the number whose orbits are
settled with sufficient accuracy for Us to ascer-
tain their idendity on their temperance, is
only about hfty-nine. The orbits OF most of
these are inclined to the plane of the ecliptic
in large angles, and in their perihelon they
come much nearer the sun than the earth
does. Their motions in the heavens are also
different from those of the planets. When a
Comet arrives within a cetain distance of the
sun, it emits prodigious fume or vapor, cal
led IT'S tail. These tails seem largest and
most splendid Immediately after they return
from the sun, because, being then hottest,
they emit the greatest quantity of yapours,
ana are always opposite those parts which
the BODY of the Comet leaves in its descent,
which is agreeable to the nature of smoke
and vaponr They also appear broader on
their upper part than near the head of the
Comet; like all vapours, the higher they
rise the more they dilate themselves. The
tails of Comets are extremely long, some of
them having been computed to be not less
than eighty millions of miles in length, and
the ,ail of the Comet, which is now visible,
INoy 1907 is computed to be three hundred