1/2 



Periodic Meteors, or supposed Asteroids : 



until certain matters of fact had been cleared up*; and assuredly M. 

 Arago is right. 



It is certain that in one and the same night an innumerable multitude 

 of these meteors have been seen in places whose geographical situa- 

 tion differs 90° in longitude and six hours in time, a circumstance 

 which gives to their appearance a duration of at least 18 hours ; our 

 night being at this period more than 12 hours, and beginning 6 hours 

 sooner than in the United Slates. 



Now^ as in the month of November the earth advances in its orbit 

 445,500 leagues in 18 hours, a change of place during which the ap- 

 pearances are incessantly succeeding one another, it would be neces- 

 sary that these meteors, if they really constitute asteroids, should ex- 

 ist by millions in the zone where they appear. But then these heaven- 

 ly bodies, which should approach so very near to the earth, must fre- 

 quently fall down upon it, from the attractive power which the mass 

 of our globe would inevitably exercise on them ; and this is what has 

 not yet been observed. 



When astronomers at the beginning of this century had successively 

 discovered Ceres, Pallas, Juno and Vesta, w^hich revolve around the 

 sun between Mars and Jupiter in orbits which have not a very great 

 eccentricity, the idea of making asteroids originate from the fragments 

 of a planet which might have been destroyed by means of an internal 

 explosion w^as already put forth ; but M. Biot remarked that, with re- 

 gard to these four telescopic stars, this hypothesis is inadmissible, be- 

 cause, according to the theory of attraction, such an explosion would 

 have necessarily given to these fragments unequal velocities of projec- 

 tion in starting from the same point, whence great unequal axes would 

 have resulted, which is contrary to observationf. 



It is known that Professor Brandes proved long ago, by correspond- 

 ing observations made in different places and often repeated, that there 

 are shooting stars which circulate with a velocity of 13 leagues, of 25 

 to a degree, in a second, at a height of 180 leagues above the surface 

 of the earthj. It is also manifest, from the observations made in the 

 United States compared by professor Olmsted, that the centre from 



* Comptes Bendus de V Jcad. de Paris, No. 23, December 1836, vol. iii. p. 663. 



+ Traite ElemeJitaire d' Astrono7nie Physique, 2d. edit., vol. iii. p. 42. 



t Tliese quantities, on the exactness of whicli we can rely, are the results of compara- 

 tive observations begun in 1793 by MM. Benzenbcrg and Brandes, and continued on a 

 greater scale, in 1833 by M. Brandes and his pupils, at Breslaw, Dresden, Leipe, Brieg, 

 Gleiwitz, Sec— Bill. Univ., vol. li. p. *203 ; Annuaire du Bureau des Loiigiiudes de Paris 

 for 1836, p. 292. 



