402 Miscellanies. 



whose perihelion distances, respectively, correspond nearly with those 

 of Venus and the Earth. It is only necessary to suppose that in some 

 planes these bodies exhibit a greater tendency to the formation of clus- 

 ters, or possibly of flattened rings, in order to account for anniversary 

 periods of remarkable showers ; since the earth revisiting the same plane 

 at the same season of the year, and at the same distance from the sun, 

 may or may not encounter one of these clusters or parts of a flattened 

 ring. But these clusters continuing to move in the same plane, the earth 

 must, if it meet them at all, do so at anniversary periods. On the sup- 

 position of a flattened ring, the node having the same radius vector as 

 the earth, these displays might occur for several anniversaries, and then 

 cease for an indefinite period, owing to the motion of the apsides of the 

 rincf ; till the anomaly which has a radius vector equal to the earth's 

 mean distance, again coincides with one of the nodes of the ring. Hence 

 the connexion between the periods of the second table, as far as regards 

 our knowledge of them is accidental, since they depend not on the or- 

 bital period of these bodies round the sun, but on the circumstance of 

 the earth's encountering one of these clusters, or planes abounding in 

 them, which is regulated by a law of distribution of these bodies in plan- 

 etary space, that must always remain unknown, for want of -data for its 

 determinatton. 



The author conjectures that the meteors termed sporadic, by Quetelet; 

 which have no common convergent point, may have their perihelia su- 

 perior to those of the periodical meteors, and their aphelia far superior 

 to that of the earth. In such a case, their orbital velocity would be as 

 great as that of the earth, or greater ; and as they move in all varie- 

 ties of direction, the earth's tangential motion does not cause them to 

 tend, relatively towards a convergent point, in nearly an opposite direc- 

 tion, as it does with meteors moving very slowly in their orbits, whatever 

 may be their true directions in space. 



A brief history of the opinions and theories of writers on this sub- 

 ject is given ; and an oversight pointed out in Prof Erman's paper, 

 quoted by the author in an oral communication of August 21st, 1840. 

 This relates to Prof. Erman's minimum relative velocity of the meteors, 

 which, instead of being 0.83, of that of the earth, may be indefinitely 

 small, and therefore in his formulae [Artronomische Nachrichten, No. 

 385, p. 9,] may give a motion of the convergent point indefinitely great. 

 The author also remarks, that the quantities neglected in Prof. Erman's 

 formulee for this motion, may produce an important effect on the result, 

 and even change its direction from a retrograde motion, as found by 

 Prof. Erman, to a direct motion as observed by Mr. Fitch, at New Ha- 

 ven, and as indicated by Prof. Forshey's observed positions of this point 

 at tw^o diflTerent dates on the night of the 10th of August last.-^Pro- 

 ceedings of the American Philosophical Society, Feb. 1841. 



