A CATALOGUE OF OBSERVATIONS OF LUMINOUS METEORS. 395 
the second class are clusters of small stars (or ‘ star-dust” of Herschel), in 
which class are many resolvable nebula. The next class are smaller bodies, 
which become visible as comets when they approach the sun. The last class 
of bodies, in the smallest state of subdivision, are cosmical clouds, composed 
of bodies no larger than we can handle or carry on the earth. 
“TI. The last class of bodies may have originated from local concentra- 
tions in space, in the same way that chemical substances crystallize from their 
solutions. The appearance of the process of crystallization leads to the con- 
jecture that this mode of concentration is more frequent and general than the 
process by which larger masses have collected. ‘The space occupied by the 
cosmical clouds may, accordingly, constitute a large part of the intrastellar 
regions. 
“II. The motions of such clouds relatively to the visible bodies of the 
universe are comparable to those ofthe fixed stars, and probably attributable 
to the same causes. When a cosmical cloud enters the sphere of the sun’s 
attraction, it can only become visible to us when its orbit about the sun is an 
ellipse of very great excentricity. 
“TV. Whatever may be the shape and size of a cosmical cloud, it can 
rarely enter the central parts of the solar system without being transformed 
into a parabolic current, which may occupy years, centuries, or thousands of 
years in completing its perihelion passage, in the form of a stream extremely 
narrow in comparison with its length. Of such streams those which the 
earth encounters in its annual revolution present themselves as a shower of 
shooting-stars diverging from a common centre of radiation. 
“V, The number of meteoric currents traversing the solar system in all 
directions is probably very great. The extreme rarity of their materials 
permits them to intersect each other mutually without disturbance. They 
may gradually shift and change their form, like rivers which slowly change 
their bed. They may be interrupted, so as to become double or multiple. 
The November meteors are probably such a current in process of formation. 
“VI. Cosmical clouds haying short periods of revolution round the sun, 
which have been assumed to explain the appearances of shooting-stars, can- 
not exist permanently without violating the laws of universal gravitation. 
«VII. The materials of parabolic currents, after passing through their 
perihelion, return to space in a state of greater dispersion than before their 
perihelion passage. In particular cases, as when the current meets with a 
planet, such great perturbations of some of the meteors may arise as to di- 
vert them from the general track, into special orbits. Such meteors may, 
from that time, be properly called sporadic. 
_ YVIII. Shooting-stars and other like celestial bodies, which in the last 
century were regarded as atmospheric, which Olbers and Laplace first main- 
_ tained might be projected from the moon, and which afterwards came to be 
regarded as planetary bodies, are in reality bodies of the same class as the 
fixed stars; and the name of falling stars, applied to them, simply expresses 
the real truth. They bear the same relation to comets which the planetoids 
etween Mars and Jupiter bear to the larger planets, the smallness of we 
asses, in both cases, being compensated for by the greatness of their number. 
_ IX. Since it may certainly be assumed that shooting-stars, bolides, and 
_aérolites only differ from each other in their comparative size, we may conclude 
that the substances fallen from the sky are samples of those of which the 
‘Stellar universe is composed ; and since in such masses no new chemical ele- 
“ment has been discovered, hitherto unknown upon the earth, the similarity 
of composition of all the visible bodies of the universe, already rendered pro- 
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