The Sun.
London, England, 1858-09-28 00:00:00

THE COMET.

On the 2d of June last Dr. Donati, of Florence,
discovered a small nebulous star. A few observa-
tions determined the character of the stranger to
be that of a comet. These observations were not
only sufficient to demonstrate the presence of a new
comet, but also to make a fair approximation to
the path of the wanderer. The comet grows in
13rightness, it follows very nearly its approximate
path, as calculated from a few of its observed posi-
tions, till it becomes a marked and remarkable ob-
ject to the naked eye, and now on every clear night
is beheld with wonder and pleasure by thousands .
Comparatively few of the present generation have
seen such aliastronomicalphenomenon. No wonder
therefore that we are assailed on all sides by the in-
quiries—What are comets? Where do they come
from? Where do they go to? Are we indebted
to the comet for our present warm weather as well
as our abundant harvest and crops of fruit ? What
is a perihelion passage? and so on. Now there is
no lack of books or teachers to supply all this in-
formation. But every man has not the books on
his shelves ;. and if they are there, he may not
have time or leisure to turn over their pages and
satisfy his curiosity. Those conversant with the
facts of astronomy, and. enthusiastic enough to dis-
play their store of knowledge to every listener,
may not meet those desirous of hearing their lore.
It is the province of the press to give sound views
and information on all the current events of the
day, and a chapter on comets will doubtless be
acceptable to many of our readers.
Before the discoveries of Newton, whose statue
at his native place has been so recently inaugurated,
the stars presented several wandering bodies, whose
orbits defied the powers of calculation of. the astro-
nomer. These were called planets and comets. If
the planets were so named for their wandering and
erratic paths, defying the skill of the astronomer to
reduce them to rule and order, the comets were pre-
eminently entitled to the character of most vagrant
bodies. The most brilliant planets failed to startle
or amaze the terrestrial beholder, so much as the
apparition of a star with a vast streaming tail,
sometimes covering a considerable portion of the
visible heavens. If the wandering planets were sup-
posed to influence the bodies and histories of men,
comets, bearing their flaming brands across the
skies, could bode nothing short of plague, fire, and
the sword to nations and empires.
After long and dreary study and most invincible
industry, Kepler reduced the orbits of the planets
to great simplicity, 137 inging them under the order of
three simple and exact laws. Their vagaries among
thi fixed stars, their advance, their retrogression,
their apparent stand still in their heavenly course,
were all shown to arise, from the deceptions of per-
spective, and from our viewing their career from
an observatory itself in constant motion. Recur-
ring to the theory of Copernicus, that the sun was
the centre, while we, like all the other planets,
were revolving round that centre in orbits, Kepler
determined the true orbits which would account for
all the apparently irregular motions of the planets
amid the other heavenly bodies. Newton then stept
in with his universal law of gravitation, and showed
that Kepler's laws were the consequence of one
simple law of attraction, combined with the laws of
motion.

Kepler suspected the comets of moving in parabo-
lic orbits, but Newton showed that they, like the
planets, are under the domain of the same physical
law. According to the Newtonian theory, irrespec-
tive of perturbations, there are but four distinct
curves, in which bodies acted upon by the laws of
gravitation can move.. These are all found in
the sections of a cone. So far as observation has
bin extended, is is doubtful whether in point of
fik all the observed orbits are not confined to one
species, the ellipse. The ellipse is an oval figure,
which most of our readers may have seen described
over and over again, while watching a gardener
laying out an oval flower bed. Ile sticks two pegs
of wood firmly in the ground, he ties the extremities
of a piece of cord together, he throws his loose ring
of cord over the two pegs, and then with a stick, he
stretches the cord over the pegs, and marks on the
ground the line whick his stick follows while he
walks round, keeping the cord always stretched
to its utmost extent. In this way he marks out an
oval line or boundary, perfectly symmetrical. This
oval is a geometrical ellipse, and the two pegs are
called its foci. According to the observation of the
motions of planets and comets, neglecting minute
deviations caused by the disturbing influences which
they exert on each other, this oval is the orbit
of all or nearly all that have been observed or
calculated. If with a cord of given length the two
pegs over which the cord is stretched, or the two
foci are made to approach very near each other, the
oval approaches closely to the figure of the circle.
Indeed, if the two pegs accurately coincided, it
would be a circle. All the planets move in ellipses
very nearly circular, or in ellipses of small eccen-
tricity. The sun is always in one of the foci of the
orbit. If, on the other hand, the foci are placed at
a considerable distance from each other, the figure
is more oval in its character, its eccentricity is
greater, and we have the orbit of a comet. As the
nearer the foci of the ellipse approach each other,
the more the ellipse approaches the form of the
circle, so the more they diverge from each other
the more the ellipse approaches to another curve,
called the parabola, which is also a conic section.
Mathematically speaking a parabola is an ellipse
the distance of whose foci is infinitely great.
According to the Newtonian laws, there is only
this difference between planets and comets—that
while the former are moving in orbits nearly circu•
lar, the latter revolve in orbits of greater eccentri-
city—in ellipses, or perhaps in the parabolas or
hyperbolas. Theoretically they might move either
in parabolas or hyperbolas ; but then, after one
visit to our system, they could never return again.
As in the case of the planets, so in that of comets,
the position of the sun is always in one of these foci.
Modern science, therefore, to a certain extent, de-
nudes the cometary appearances of the vague terrors
they once excited. They are reduced to the level of
such ordinary attendants of the solar system as the
planets—ruled by the same laws. Does science sug-
gest no real terrors in place of the vague fears of
irrnorance ? The paths of the planets being nearly
circular—nearly all in the same plane—their dis-
tances from each other vast, and the sun near the
centre of their orbits, no fear exists that they can
ever cross each other's path and come into collision.
It is not so with comets ; they whirl round the sun
in every possible direction ; the planets all move
one way, and not far removed from one imagi-
nary surface or plane ; the comets move in
every plane, and some in the direction of the
planets, and others in the opposite. For anything,
therefore, that can be determined, either some
comet which has not visited our system within
historic period, or some one whose path has been
determined, might come into collision with a planet.
What would be the effect of this collision is indeed
a startling question, and one not easily answered.
Whiston accounted for the universal Deluge by sup-
posing our planet involved in the tail of a passing
comet. This may be said to be the vague surmise of
an imaginative individual, not the determination of
a sound mathematical and physical philosopher.
Yet Lalande, the astronomer and calculator of
cometary orbits, describing, in 1773, what would be
the effect of a comet passing within 45,000 miles of
the earth, though he could see no danger of so near a
proximity, so frightened the Parisians that many died
of sheer terror. The passage of a comet so near
the earth would, he thought, raise the waters of
the ocean to such a height, they would sweep over
the continent of Europe, and carry all its inhabi-
tants with their habitations into the sea. It is
true he gave us most promising assurances of the
thousands, nay millions, of chances there were in
our favour, that no comet whose orbit crossed that
of our planet, would ever cross that orbit suffi-
ciently near the earth to do such damage. Still
the science of probabilities is not a very assuring
one, when we know not how many
,comets there
are, and have an uncomfortable suspicion that al
_ty be set at nought bj
its assurances might any daysome new visitor.—Daily News.

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On being launched into the Bow-creek or
down the river.
the Essex section of the works, considerable
cause her nearly' to fall some serious mishap in drifting
Lea river, from .
lay -as incurred m getting her down the stream to the
Thames,m and when that was fairly accomplished the tide was
on the turn. The three tugs which had hold of the huge
vessel put on their united power to get the Derrick to the
buoys opposite the entrance to the East India Docks. Her
progress, however, was considerably retarded by the timber
of the ways, which had got fixed in some way to her bottom.
The force of the strong ebb, as it came uponher broad bow, also
tended to check her advance. Hawsers were at length got
to the buoys off the East India Dock, but owing to the heavy
strain
wn the upon
ver . them, they failed, and the vessel began to drift
do ri A fourth tug came to her aidond as it was
apparent that they could not bring her up in her present
position and the then state of the tide, it was arrange,: that
she should be allowed to pursue her course steadily through
Woolwich to a point where she would be beyond the strong
influence of the ebb, The tugs kept in attendance upon
her, and in the lower part of the Reach near the Galleons
she was brought to. On the return of the flood tide on
Sunday morning, the tugs again got hold of her, and she
was safely brought back to Blackwall and secured to the
buoys. The Derrick was in charge of one of the most ex-
perienced pilots, and her escape from injury herself, or
damaging other craft as she drifted down the Thames,
seems most surprising. As the vessel was being brought
to the buoys on Saturday afternoon, several men were hurt by the capstan, and one had to be taken to the Poplar
Hospital,