FURTHER RESEARCHES OF REICHENBACH--THEORY OF METEORS--STABILITY OF
THE SOLAR SYSTEM--DOCTRINE OF A RESISTING MEDIUM.
The able and original researches of the celebrated Reichenbach, who has
made meteoric phenomena the subject of long-continued and enthusiastic
investigation, have attracted the general attention of scientific men.
It is proposed to present, in the following chapter, a brief _resumé_
of his views and conclusions.
1. _The Constitution of Comets._--It is a remarkable fact that cometary
matter has no refractive power, as is manifest from the observations of
stars seen through their substance.[20] These bodies, therefore, are
not gaseous; and the most probable theory in regard to their nature is
that they consist of an infinite number of discrete, solid molecules,
at great distances from each other, with very little attraction among
themselves, or toward the nucleus, and having, therefore, great
mobility. Now Baron Reichenbach, having carefully examined a great
number of meteoric stones, has found them for the most part composed
of extremely minute globules, apparently cemented together. He hence
infers that they have been comets--perhaps very small ones--whose
component molecules have by degrees collected into single masses.
2. _The Number of Aerolites._--The average number of aerolitic falls
in a year was estimated by Schreibers, as previously stated, at 700.
Reichenbach, however, after a thorough discussion of the data at
hand, makes the number much larger. He regards the probable annual
average, for the entire surface of the earth, as not less than 4500.
This would give about twelve daily falls. They are of every variety
as to magnitude, from a weight of less than a single ounce to over
30,000 pounds. The Baron even suspects the meteoric origin of large
masses of dolerite which all former geologists had considered native
to our planet. In view of the fact that from the largest members of
our planetary system down to the particles of meteoric dust there is
an approximately regular gradation, and that the larger, at least
in some instances, appear to have been formed by the aggregation of
the smaller, he asks may not the earth itself have been formed by an
agglomeration of meteorites? The learned author, from the general scope
of his speculations, would thus seem to have adopted a form of the
nebular hypothesis somewhat different from that proposed by Laplace.
3. _Composition and mean Density of Aerolites._--A large proportion of
meteoric stones are similar in structure to the volcanic or plutonic
rocks of the earth; and _all_ consist of elements identical with
those in our planet's crust. Their mean density, moreover, is very
nearly the same with that of the earth. These facts are regarded by
Reichenbach as indicating that those meteoric masses which are daily
becoming incorporated with our planet, have had a common origin with
the earth itself. Baron Reichenbach's views, as presented by himself,
will be found at length in _Poggendorf's Annalen_ for December, 1858.
_Stability of the Solar System._--The well-known demonstrations of
the stability of the solar system, given by Lagrange and Laplace,
are not to be accepted in an unlimited sense. They make no provision
against the destructive agency of a resisting medium, or the entrance
of matter into the solar domain from the interstellar spaces. In
short, the conservative influence ascribed to these celebrated
theorems extends only to the major planets; and even in their case it
is to be understood as applying only to their mutual perturbations.
The phenomena of shooting-stars and aerolites have demonstrated the
existence of considerable quantities of matter moving in _unstable_
orbits. The amount of such matter within the solar system cannot now be
determined; but the term probably includes the zodiacal light, many,
if not all, of the meteoric rings, and a large number of comets. These
unstable parts of the system are being gradually incorporated with the
sun, the earth, and doubtless also with the other large planets. It is
highly probable that at former epochs the quantity of such matter was
much greater than at present, and that, unless new supplies be received
_ab extra_, it must, by slow degrees, disappear from the system.
The fact, now well established, of the extensive diffusion of meteoric
matter through the interplanetary spaces has an obvious bearing on
Encke's theory of a resisting medium. If we grant the existence of such
an ether, it would seem unphilosophical to ascribe to it one of the
properties of a material fluid--the power of resisting the motion of
all bodies moving through it--and to deny it such properties in other
respects. Its condensation, therefore, about the sun and other large
bodies must be a necessary consequence. This condensation existed in
the primitive solar spheroid, before the formation of the planets:
the rotation of the spheroid would be communicated to the coexisting
ether; and hence, _during the entire history of the planetary system,
the ether has revolved around the sun in the same direction with the
planets_. This condensed ether, it is also obvious, must participate in
the progressive motion of the solar system.
But again; even if we reject the doctrine of the development of the
planetary bodies from a rotating nebula, we must still regard the
density of the ether as increasing to the center of the system. The
sun's rotation, therefore, would communicate motion to the first and
denser portions; this motion would be transmitted outward through
successive strata, with a constantly diminishing angular velocity.
The motion of the planets themselves through the medium in nearly
circular orbits would concur in imparting to it a revolution in the
same direction. Whether, therefore, we receive or reject the nebular
hypothesis, the resistance of the ethereal medium to bodies moving
in orbits of small eccentricity and in the direction of the sun's
rotation, becomes an infinitesimal quantity.
The hypothesis of Encke, it is well known, was based solely on the
observed acceleration of the comet which bears his name. More recently,
however, a still greater acceleration has been found in the case of
Faye's comet. Now as the meteoric matter of the solar system is a
_known_ cause for such phenomena, sufficient, in all probability, both
in mode and measure, the doctrine of a resisting ethereal medium would
seem to be a wholly unnecessary assumption.