The weekly ledger., 1857-05-30

DC conceived Sucn tnlDg as negative shad-
ow momentary impression made upon the
luminiferous ether behind the comet. this
would represent, in some degree, the concep-
ton such phenomenon irresstbly calls up.
The particles that form the tails of comets,
and the extreme portion Of the nebulous en-
velope about the nucleus, having passed be-
yond the sphere Of active attraction of the
head, can never return, but are lost to our
view and knowledge in space. Several
known comets, that in early times were de-
scribed as exceedingly terrific" have lost
much of their splendor and magnifcence;
and comets Of recent date and short period,
are decreasing in brightness, and may finally
be precipitated upon the sun.
OF the effects of comets upon the solar
system Of the earth, we may very confident
ly draw conclusions which fully substantiate
the stability of our system. The body of
the great comet of lS43 passed its perihelion
at distance not exceeding one seventh of
the suns diameter; ey- sriencing at that dis
tance an intensity Of heat more than Al 900
times greater than the earth receives; or 25
times more intense than is required to melt
cornelian, agate or rock crystal While sub
ject to this heat it passes through its orbit at
the rate of 366 miles per second The COM
ct of 1850 passed its perhilion at the dis
tance Of one sixth of the suns diameter, and
at the rate of 200 miles per second.
On account Of the great eccentrcity Of
the orbits of comets, they must, in many in
stances, intersect or pass very near the or
bits of some of the planets. Lexel and
Burcthard'S comet Of 1867 passed Jupiter at
distance Of only one-l16th part of the di-
ameter of that planets orbit. On the 2sth
of June, ITO, its distance from the earth
was only six times that of the moon-ths be-
ing the nearest observed approach of comet
to the earth. In 1919 it again approached
Jupiter within the one-49lst part of the di-
ameter of that planets orbit, and thus being
only four-ffths Of the distance of that planet
from its 4th satelitel BY this remarkable
rencontre with the system of Jupiter's satel-
lites, none Of their motions, in their well
known orbits, suffered the slightest percepti-
BILE arrangement, but their repulsive power
threw out the comet, and its orbit was SO
changed that it has never returned
Halley's 76 year comet has also suffered
from the perturbations of Jupiter and Saturn
-Clairaut having computed that it would be
retarded 5ls days by the former, and 100
days by the latter, in its appearance in 1859,
with probable error of thirty days. 1t ac-
tually reached its periheion within the pre-
scrbed limit of error
The third comet Of 1913, (Fay's) ap-
preached so near to Jupiter in 1889 and 40,
hot ba ,,lo paffr Of o4t
tenth part Of the Suns, and must have pro-
duced considerable alteration of the comets
orbit. Its period is about seven years, tat
there is no doubt that on some future oeca-
sion Jupiter may possibly cause it to move
in such an orbit as to become invisible.
The comet of 937 recorded by the Chinese
astronomers, remained, according to Du Sc
jeur, twenty-four hours within a mean dis
tance of two millions Of miles from the
earth
Biela's comet presents the first example of
the orbit of comet intersectng that of the
Earth 1t is very small and hardly visible to
the naked eye even when brightest. This is
the comet which, on the 18th of January,
1916, presented the extraordinary spectacle
of the primitive body separating into two
cometsl The phenomenon struck astrono-
mers with amazement, and gave an interest to
this wanderer in our system, which recent
predictions seem determined to keep alive.
Each comet pursued its own path, and before
they were lost to the telescope, their elements
were determined sufficiently close to predict
their re-appearance, which actually took place
in 1852, although made under circumstances
unfavorable for observing They performed
their orbits without exercising any percepti-
BILE amount of pertubative gravitaton on
each other, as, indeed, from the minuteness of
cometary masses, we might have reasonably
expected.
The orbit of this comet so nearly intersects
that of the Earth, that an actual collision is
not impossible, and must happen in the course
of some millions of years. if neither orbit
varies. Should it approach as near the earth
as Lexel's comet did to Jupiters system
there is not the slightest doubt but that its
orbit would be eifectually changed, and the
comet, perhaps never again be seen. We
must not confound the passage of any cosm-
cal body through the Earth's orbit, with its
or collision with our globe. Great
excitement was produced in 1882 by the an
Of the orbits Of the Earth and
this comet intersecting each other, but when
this passage took place on the Goth of Octo-
Der. it required full month before the Earth
reached the point Of intersection Bearing
in mind that the Earth moves in its orbit at
the rate of nearly l,640,OO0 miles per day, it
is easily perceived how remote was the chance
of collision.
We have already observed that the tails of
some of the larger comets are greater than
the distance of the Earth from the Sun, and
the computations Of astronomers show that