AEROLITES. 129 



gnribe a retrograde orbit round the Sun. It also follows, 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 interruption in 

 the meteoric ring, that is to say, to intervals occurring be- 

 tween the asteroid groups, or, according to Poisson, to the ac- 

 tion of the larger planets* on the form and position of thij 

 annulus. 



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

 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 in- 

 candescence. They undeniably exhibit a great degree of gen- 

 eral identity with respect to their external form, the character 

 of their crust, and the chemical composition of their principal 

 constituents. These characteristics of identity have been ob- 

 served 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, however, met by many excep- 

 tions regarding individual points. What differences, for in- 

 stance, 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 cele- 

 brated by Pallas, or those which I brought from Mexico,t all 

 of which contain 96 per cent, of iron, from the aerolites of 

 Siena, in which the iron scarcely amounts to 2 per cent., or 

 the earthy aerolite of Alais (in the Department du Gard), 

 which broke up in water, or, lastly, from those of Jonzac and 

 Juvenas, which contained no metallic iro'n, but presented a 



* " 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 cii'culation may be very diflferent 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- 

 merits, p. 306, 307. 



t Humboldt, Essai Politique sur la Nonv. Espagne (2de edit.), t. iii. 

 p. 310. 



F 2 



