METEORS OF AUGUST AND NOVEMBER. 109 



tered isolated nebulse, or swarms or clusters of these asteroids. Perhaps the 

 group, ring, or lens, which now furnishes the August or November displays, 

 may have undergone, in the position of its plane, and line of apsides, such 

 variations as to embrace a part of these remarkable epochs. On the hypothe- 

 sis of a single cluster, with a yearly or half yearly period, this event would not 

 be improbable. On the hypothesis of a ring, a change of plane, to a great ex- 

 tent, could hardly be considered probable. It seems more natural, however, 

 since the relative direction of these asteroids in ancient displays, is "unknown, 

 in the absence of proof of identity with the groups of recent appearance, to 

 regard the ancient displays of Quetelet's catalogue as isolated clusters, whose 

 meeting with the earth was purely accidental; that is to say, was regulated by 

 a law of the distribution of these single bodies, and their groups, in space — 

 which must always remain unknown for want of data for its determination. 



§ V. Of THE RESPECTIVE PLAUSIBILITIES OF THE HYPOTHESIS OF A SINGLE 



Cluster, with a half yearly or yearly Period, and that of a conti- 

 nuous Ring, for the periodical Meteors of August and November. 



In order to judge of the plausibility of the theory of a single cluster and that 

 of a continuous ring for the August and November asteroids, I here subjoin 

 the results of a computation based upon these respective hypotheses; using, 

 in connexion with them, the most plausible values of 5/, a, and h, derived from 

 the preceding tables. These values are not sufficiently exact to furnish the 

 particular elements of the orbits of these meteors. They serve, however, to 

 show, by specific examples, that the general conclusions already announced 

 concerning the character of some of their elements, the perihelion distance and 

 semiaxis major, for instance, have not been drawn at random. The results 

 would also be modified by the application of the effect of the earth's distur« 

 banco, and of the resistance of its atmosphere. 



viii. — 2 c 



