AEROLITES. 117 



from the views thus developed, that the non-appearance, 

 during certain years, in any portion of the Earth, of the two 

 streams hitherto observed in November and about the time 

 of St. Lawrence's day, must be ascribed either to an inter- 

 ruption in the meteoric ring, that is to say, to intervals occur- 

 ring between the asteroid groups, or, according to Poisson, 

 to the action of the larger planets* on the form and position 

 of this annulus. 



The solid masses which are observed by night to fall to the 

 earth from fire balls, and by day generally when the sky is 

 clear, from a dark small cloud, are accompanied by much 

 noise, and although heated, are not in an actual state of 

 incandescence. They undeniably exhibit a great degree of 

 general identity with respect to their external form, the cha- 

 racter of their crust, and the chemical composition of t"heir 

 principal constituents. These characteristics of identity 

 have been observed at all the different epochs and in the 

 most various parts of the earth in which these meteoric 

 stones have been found. This striking and early- observed 

 analogy of physiognomy in the denser meteoric masses is, 

 ho wever, met by many exceptions regarding individual points. 

 What differences, for instance, do we not find between the 

 malleable masses of iron of Hradschina in the district of 

 Agram, those from the shores of the Sisim in the government 

 of Jeniseisk, rendered so celebrated by Pallas, or those which 

 I brought from Mexico f, all of which contain 96 per cent. 



* " It appears that an apparently inexhaustible number of bodies, too 

 small to be observed, are moving in the regions of space, either around 

 the Sun or the planets, or perhaps even around their satellites. It is 

 supposed that when these bodies come in contact with our atmosphere, 

 the difference between their velocity and that of our planet is so great, 

 that the friction which they experience from their contact with the air 

 heats them to incandescence, and sometimes causes their explosion. If 

 the group of falling stars form an annulus around the Sun, its velocity 

 of circulation may be very different from that of our Earth ; and the 

 displacements it may experience in space, in consequence of the actions 

 of the various planets, may render the phenomenon of its intersecting 

 the planes of the ecliptic, possible at some epochs, and altogether im- 

 possible at others." Poisson, Recherches sur la Probability des Juge- 

 mente, p. 306, 307. 



t Humboldt, Essai politique *ur la Nouv. Eswagne (2de e"dit.), t. iii. 



310. 



