96 RESEARCHES CONCERNING THE PERIODICAL 



nary occasions are asteroids, having their perihelia more aggregated together 

 as distance from the sun diminishes, is a piori rendered probable from the 

 known analogies of the solar system. This general classification of these shoot- 

 ing stars, founded only on probable grounds, seems to be all the inference that 

 we are able to draw from the existence of an actual convergent point on com- 

 mon nights, conformable to the theoretic, and from the facts known respecting 

 their relative velocities. Of the particular elements of motion of the individu- 

 als seen, there are no grounds for forming even a conjecture. The simple cir- 

 cumstance of this compensation of their true directions, and true normal velo- 

 cities, while it warrants the general conclusion that they are inferior asteroids, 

 also leads to a belief that the planes of their orbits are promiscuous in po- 

 sition. 



The impossibility of determining the relative direction of single meteors, on 

 ordinary nights, by observations at a single station, and the sources of error 

 pointed out chiefly by Bessel," in regard to duration, absolute time, position 

 of point of appearance and vanishing, and the uncertainty whether the visible 

 path to observers in different stations is common, must, even when several sta- 

 tions are employed, hinder, if not entirely frustrate, all our attempts to deduce 

 the cosmical elements of motion of aay one of the meteors seen on ordinary 

 nights. Hence it would seem that if the elliptic elements of any one of these 

 asteroids are ever to be known, it must be chiefly by means of corresponding 

 observations on those extraordinary occasions when the occurrence of a new 

 feature, not present on common nights, enables us to determine with precision 

 their relative directions by observations at a single station. 



§. II. — Division 2. — Of the convergent Point of the relative Paths of 

 Meteors on the Occasions of extraordinary Displays. 



The ordinary number of meteors visible by a single observer is, according to 

 Olbers,'"* Quetelet,^' Herrick,^* and others, about eight per hour. Those occa- 

 sions in which a greater number is seen are more or less extraordinary. In 

 most instances of these extraordinary displays, another circumstance is noticed 

 on careful observation. The relative directions or deflections from the anti- 



*3 Uber Sternschnuppen, — already quoted. ^* Jahrbuch, for 1838, p. 325. 



" Catalogue, (fee, p. 12, 13. ^^ Silliman, vol. xxxv., p. 172. 



