Von Hoff' on the Origin of Meteoric Stone*. 295 



have passed, or friction of the masses in the atmosphere, or the 

 compression of the latter caused by the falling bodies, can exer- 

 cise extremely little, or perhaps no influence whatever, on the in- 

 ternal and essential constitution of aerolites ; and that it still re- 

 mains even doubtful if the luminous phenomena exhibited by 

 the fallen meteoric stone is to be attributed to friction in the at- 

 mosphere and compression of the air. 



In the case of meteoric stones, which have fallen by day, a 

 feeble display of light only has been observed ; but, on the other 

 hand, a small cloud frequently accompanies the falling bodies, 

 or precedes the descent. As this cloud probably consists of va- 

 pours which are intimately connected with the luminous pheno- 

 menon, all that has been said of the latter applies equally to the 

 former. 



Fourthly, Besides the luminous phenomenon which accom- 

 panies the fall of meteoric stones, and lasts but a short time, fire 

 and smoke occur as still more transient, almost momentary phe- 

 nomena, which are of the highest importance in explaining the 

 origin of the phenomenon. 



In every fall of a meteoric stone, and at the time when the 

 falling body is still at an extremely considerable height above 

 the surface a height amounting probably to many miles a 

 very loud momentary explosion is heard, like a report or peal of 

 thunder, or crackling noise, and which is very distinctly audible 

 at great distances. 



This momentary explosion is least easily explained by the 

 idea of the lunar origin of meteoric stones. If such a mass as 

 a detached fragment of rock from the moon fell towards the 

 earth, what could produce on it a momentary violent effect in 

 a region where the earth's atmosphere if, indeed, it extends so 

 far must be so attenuated, that it may almost be compared to 

 empty space ? Why should there ensue an apparently tremen- 

 dous explosion in that region, and not rather in the densest 

 portion of the atmosphere, where the reaction of the latter on 

 the penetrating solid bodies must be the most powerful ? That 

 the explosion really occurs at such considerable heights is de- 

 monstrated partly by observations made on the parallaxes of 

 such meteors, and partly by the time which intervenes, in falls 



