Edwardsville spectator. [volume] (Edwardsville, Ill.) 1819-1826, 1819-09-18

GILES JOLTER, Jun.
FROM THE PErERsBuneH INTELLIaENcEn.
COMETS.
Theie is no part of astronomy less
understood, or which excites more the
astonis lment of the uniformed and the
curiosity of the learned, than the pheno-
mena d comets. This part of the sci
ence o natural philosophy is yet in its
infancy; and Notwithstanding the ingeni-
Gus labors of Sir Isaac Newton, De La
Lande, and La Place, we know very little
more of comets than the ancients did,
All the phenomena of comets for the last
century have been carefully observed;
and this forms the principal information
which we possess. In regard to their
real motions From whence they came
or where they go of what materials
they are composed, whether hot or cold !?
These are questions that remain to be
solved by future astronomers. OF the
return of comets, we have no certain
proof; although it is extremely proba-
bic, and the elements of ninety-seven
comets have been calculated by Laplace.
The following are the chief phenomena
which have been observed:
|. Comets which move according to
the order Of the signs, do all, little be-
fore they disappear, either advance slow
er than usual, or else go retrograde, if
the earth be between them and the sun-
andmove more swiftly ifthe earth be situ-
ated in contrary part. On the other hand,
those which proceed contrary to the or
derof the signs, proceed more swiftly than
usual, if the earth be between them and
the sun; and more slowly or go retro
grade when the earth is in contrary part.
2. So long as their velocity is in
creased, they move nearly in great cir
Giles; but towards the end of their course,
they deviate from these circles; and as
often as the earth proceeds one way, they
go the contrary way.
3. The light of their bodies, or nuclei,
increases in their recess from the earth
towards the sun; and, on the contrary,
decreases in their recess from the sun.
4. Their tails appear the largest and
brightest Immediately after their transit
through the region of the sun, or after
their perihelion.
5. Their tails always decline from
just opposition to the sun towards those
parts which the bodies or nuclei pass
over in their progress through their Or
bits.
6. This dec lination, ceterfs faribuS, is
the smallest when the heads OF nuclei
approach nearest the sun; and is less
still nearer the nucleus of the comet,
than towards the extremity of the tail.
7. The tails are somewhat brighter,
and more distinctly defined in their con-
vex than in their concave part.
8. The tails always appear broader at
their upper extreme than near the cen
tire of the comet.
9. The tails are always transparent;
and the smallest stars appear through
them.
The nucleus, which is sometimes call
ed the head or body of the comet, view
ed through a telescope, shews very
different face from those of the fixed stars
or planets. They are liable to apparent
changes, which Sir Isaac Newton as
cribes to changes in the atmosphere of
comets.
Hevelius observed of the comet of
1861, that its body was of yellowish
color, very bright and conspicuous, but
without any gllttering light; in the mid
die was dense rudy nucleus, almost
equal to Jupiter, encompassod with
much fainter, thinner matter. February
5th, its head was somewhat bigger and
brighter, Of gold color; but its light
more dusky than the rest of the stars;
here the nucleus appeared divided into
several parts. February 9th, the disk
was lessened; the nuclei still existed,
though less than before; one of them
on the lower part of the disk, on the left,
much denser and brighter than the rest;
its body round, and representing a very
lucid little star; the nuclei still encom-
passed with another kind of natter
February 10th, the head somewhat more
obscure, and the nuclei more confused ;
but brighter at top than bottom. Febru-
airy 18th, the head diminished much,
both inmagnitude and brightness. March
I'd, its roundness little impaired, its
edges lacerated, &c. March 28th, very
pale and exceeding thin; its matter much
dispersed; and no distinct nucleus at all
appearing.
Weigelius, who saw the comet of 1864,
the moon and little cloud illumined by
the sun at the same time, observed that
the moon. through teIescope, appeared