New Orleans daily crescent., 1860-10-22

Enck's comet, which revolves about the sun in
81 years. has been observed to complete its revo-
lion in constantly shortening period, showing
that it is being drawn inward towards the sun.
This fact has led to the general conclusion by astro
nomers, that the planets are moved in a resisting
medium, far more attenuated than our atmosphere,
but still sufficient to affect their motions. If this
is So it follows by strict necessity that earth
and its sister orbs are all winding spirally towards
the sun, and that they must eventually strike
against it and become Incorporated with its mass.
The time required for this purpose belongs to those
inconeeiyable periods with which geology and as
tronomy have to deal The resisting medium is so
exceedingly attenuated that it exerts but slight
influence on the comets, which are themselves
masses of the very thinnest vapor, and its influence
would, of course, be very much less on the dense
matter of the planets.
Astronomical observations, with all their won
derful delcacy, have yet failed to detect the slight
est progressive shortening in the periods of reyo-
luton of any of the planets 1t is curious, how
ever, to note the multiplied obstacles which pre-
vent the perception of this fact, if it does exist.
ALI the measures of these revolutions are shorten
| ing with the revolutions themselves. If we begin,
for instance, with the earth, the problem sis to
| ascertain whether the time occupied by the earth
| in its journey around the sun is gradually becom-
ing shorter. The first plan that suggests itself is
to compare this with the rotation of the earth upon
its axis to whether the year occupies the same
number of days and hours and seconds that it did
in former times. But if the earth is gradually
cooling, it is contracting in size, and its rotations
on its axis are becoming more rapid; in other
words, the day is shortening with the year ; and if
the measure shrinks just in proportion to the thing
measured we cannot tell whether the latter is be-
coming shorter or not.
II we take the time of the revolutions of the
| moon around the earth a standard, the same re-
| ssting medium would draw the moon towards the
| earth, and shorten the month also with the year.
If we resort even to the less satisfactory measure
of the suns rotation his axis, his bulk is also
| diminishing by the radiation of his heat, and the
| period of his rotation is consequently becoming
shorter. In brief, from the two of radiation
and the resisting medium, all the times and dis
tances which could be used to measure the earth's
distance from the sun Tor the period of its annual
revolution) are shortening together. So that the
differences in the extent Of the several contradic
tions are the only means left for detecting by OBJ
servation the approach of the earth to the sun, il
such approach is really taking place. These differ
i ences would doubtless reveal themselves in the
/ course of generations to refined astronomical OBJ
servations.
If the earth and the sun are gradually becoming
cold, this winding of the earth towards the sur
would tend to keep up its warmth, and it may be q
wise provision for prolonging, by some millions o
years, the continuance of animal life upon oul
globe. But this period must come to a close, fol
if there is resisting medium pervading the space
between US and the sun, the final destiny of the
earth is to curve gradually inward till, with We
locty hundreds of times greater than that of can
non ball. it dashes itself with an awfully sublime
crash into the mass of the sun.
tScientife American.