The Press.
London, England, 1857-08-08 00:00:00

THE PRESS, AUGUST 8, 1857.

chances exist against such an exact combination of
circumstances as should produce that result. Arago
computes them at 280,000,000 to 1. Upon the effect
of such a collision, Mr. Hind writes :
As regards the chance of meclisnical danger, so to
speak, consequent on the actual shock, if filch it can be
termed, of a comet, even though it were moving in an
opposite direction to that of the earth iu her otbit (or with
a possible velocity of some forty miles per second ), we may
rest assured there are few, if any, of these bodies coasti-
tilted of materials of sufficient density or solidity to pro.
duce very unpleasant effects in the event of a collision.
Popular apprehension, when coiuet•panics have arisen,
has been almost exclusively confined to this view of the
kind of danger involved in an encounter with a comet—
the blew of a large mass capable of producing by the
mere force of concussion the most disastrous conse•
quences to mankind. Such an occurrence, however, is
by no means consistent with our present knowledge of
the nature of comets. At the worst, a direct collision
would perhaps be comparable only as regard..., the
mechanical effect upon the earth to a meeting with a huge
cushion. . .

Neither is there any reason for apprehension of the
effect of a ccmet's attraction upon the waters of our globe,
occasionally hinted at in astronomical works, chiefly in
those of the last century. It may be mathematically
demonstrated, that, even allowing a comet to be of nearly
equal mass with the earth, it could notremain long enough
in a position to operate upon the ucean in such a manner
as to overwhelm the continents, and thus lead to calami-
tous consequences. Those who may be curious on this
subject, a ill find ample information in a work published
many years since by Du Sejour, a well-known French
geometer, entitled" Essai stir les Cometes."
Dismissing, then, the idea of any mechanical danger
from actual collision, we have to notice the possible effects
of a sudden commingling of the nebulosity of a comet with
the earth's atmosphere, an occurrence invo?ving considera-
tions of quite a different nature from the preceding. With
our actual knowledge (imperfect though it may be) of the
existence and probable origin of those tremendous forces
so conspicuously visible in their effects in the comets of
111t40, 1M33, etc., and which, as we have seen, there is
every reason to suppose analagous to electricity and
magnetism in their most powerful states of development,
it is hardly tol much to say that our immersion in the
head of such a comet might be attended with serious con-
sequences. Whether we should escape with the tempo-
rary derangement of our comnasses, the disorganisation of
our telegraphs, with electrical storms of unprecedented ex-
tent and violence, and startling exhibitions of aurora;, etc.,
or whether the electrical equilibrium of the atmosphere
would be so completely overthrown as to occasion events
of a disastrous character. and more easily imagined than
described, must necessarily be open to speculation.

Upon many other points of interest—the velocity
and appearance of comets, on their duration of visi-
bility and distance from the earth, upon the effect of
the attractions of the planets, and upon the part of
the heavens the coming comet will first b visible—
we must refer the reader to this intelligent little
treatise, which is certain to achieve decided popu-
larity.