=a 
A CATALOGUE OF OBSERVATIONS OF LUMINOUS METEORS. 419 
third chapter contains a catalogue of stonefalls, in chronological order ; and the 
4th-11th chapters, discussions of various questions in the theory of meteors, 
such as :—the relative number of meteoric falls during the different parts of 
the day, or year; the coexistence of different forms of meteoric matter in the 
same rings; meteoric dust; the stability of the solar system, and the hypo- 
thesis of a resisting medium; the extent of the atmosphere as indicated by 
meteors ; the chemical and mechanical theories of solar heat; and the ex- 
planation of temporary and variable stars by the revolution round them of 
meteoric rings. In the 12th chapter, the rings of Saturn are regarded as 
examples of such formations, the principal gap or interval between them 
being thus especially accounted for. The 13th chapter treats of the zone of 
asteroids ; and in the concluding chapter of the work the Nebular Hypothesis 
is represented as giving an intelligible explanation of the origin of meteoric 
streams *. A condensation of nebulous matter, “it is thus seen, accounts 
satisfactorily for the origin of comets, aérolites, fireballs, shooting-stars, and 
meteoric rings.” 
In summing up the result of his conclusions (pp. 120-122), Dr. Kirkman 
cites the recent calculations of Leverrier and Schiaparelli on the remarkable 
connexion observed to exist between Tempel’s comet (I. 1866) and the 
group of the November meteors; of which group the comet appears to con- 
stitute the nucleus. The probable periodic time (about 105 years) of the 
August meteoric ring is also noticed, the similarity of its elements to those 
of the orbit of the third comet of 1862, and the remarkable circumstance, 
first pointed out by Schiaparelli, that a nebulous mass drawn into the solar 
system from without will be deformed in its approach, so as to pass the sun 
in a very narrow stream, and that if it returns in an elliptic orbit it will, 
after a certain number of revolutions, be converted into a continuous ring of 
material substance. The aérolitic epoch of the 27th—30th of November may, 
perhaps, be produced by such a ring connected with Biela’s comet, near the 
orbit of which the earth annually passes at about that date. 
With regard to aérolites, it is observed that they are more frequent 
(1) by day than by night, 
(2) in the afternoon than in the forenoon, 
(3) when the earth is in aphelion than when it is in perihelion. 
The first of these conditions is accounted for by the difference in the num- 
‘ber of observers. The second indicates that the orbital motion of aérolites 
is generally direct; and the third is dependent on the greater length of the 
day in the apheliac than in the periheliac portion of the year. The asteroidal 
space between Mars and Jupiter is not impossibly a wide meteoric zone in 
which the largest aggregations are visible to us as the minor planets. The 
zodiacal light may also be regarded as an immense swarm of meteor aste- 
roids; and, finally, the meteoric theory of solar light and heat is included 
in the treatise as a consequence of the same form of the nebular hypothesis. 
* At p. 30, speaking of the radiant-point of the 19th-20th of April meteoric shower, 
Dr. Kirkwood states, on Mr. Greg’s authority, that it is about Corona. This mistaken 
estimate of its position, from an imperfect view of the phenomenon on the night of the 
20th of April, 1863, was given by Mr. A. 8. Herschel in a lecture delivered a few days 
later, at the Royal Institution, in London. The position of the radiant-point was more 
accurately determined in the following year (see these Reports for 1864, p. 98), and it was 
then found to coincide with the place assigned to it by Herrick, in 1839, “ near # Lyre.” 
