292 Von Hoffon the Origin of Meteoric Stones. 



in which it was discharged from the cannon ; or they may under- 

 go some change during their transit through the space between 

 the moon and the earth. 



The condition of meteoric stones, when we regard them as 

 fragments of mountain rocks, affords us no grounds for believ- 

 ing, that, during their passage, they have suffered any other 

 change than a sort of slight melting of the surface, which is 

 made known by the black crust with which they are enveloped. 

 This crust is extremely thin, and penetrates to a certain extent 

 the interior of the meteoric stone, only where there are fissures. 

 The interior has so completely the aspect of a granular com- 

 pound mountain rock, and the iron of the masses of iron is so 

 perfectly compact, that when we assume that these masses have 

 been torn from the moon, constituted as we find them, we must 

 also admit that, during their passage, they have suffered no 

 other alteration than the very slight one operated on their external 

 surface, by which a thin crust has been produced ; and some- 

 times the breaking up of the mass into several pieces. Berze- 

 lius seems to entertain the same view on this point. 



When we consider that a discharged cannon-ball does not be- 

 come red-hot during its passage through the lowest and densest 

 portion of the air ; and that a rifle-ball, composed of easily fu- 

 sible lead, penetrates wood of ordinary hardness, without losing 

 its roundness, thus shewing that it has not become soft during 

 its passage, we can understand that masses ejected by the moon, 

 notwithstanding the much greater rapidity of their motion than 

 that of cannon-balls, cannot be altered to any depth in their in- 

 terior, or melted, merely by friction in the atmosphere, whose 

 denser portion they reach only at the end of their course. It is 

 therefore difficult to explain, according to the lunar hypothesis, 

 the phenomena which always accompany the fall of meteoric 

 masses, and which can be produced with extreme difficulty dur- 

 ing the passage, however rapid, of a difficultly fusible solid body 

 through the atmospheric air. 



The phenomena of this description are the following : The evo- 

 lution of light, which can only be perceived at night, lasts but 

 a short time, and enables us to follow the course of the falling 

 body. The luminous body generally appears as a more or less 

 round ball of fire, which often drags a luminous tail after it, 



