Von Hoff on the Origin of Metemic Stones. 293 



and sometimes emits sparks. If we assume that the meteoric 

 mass already formed was projected from the moon in a solid 

 condition, we must explain the continued evolution of light for 

 a certain time, by supposing either that it was ejected in a red- 

 hot condition, or that it was heated to the red-hot state, or to 

 that of fusion, by friction in the medium through which it pur- 

 sued its course. It would also be necessary to explain by this 

 high degree of heating, the flying off of separate fragments, 

 thus giving rise to sparks, and likewise the fiery tail in so far as 

 it is not to be regarded as an optical deception. 



But there are several circumstances which are opposed to this 

 assumption. Firstly, An ejected mass from the moon would 

 pursue by much the greater part of its course towards the 

 earth, through a medium so extremely rare, that one can with 

 difficulty admit an elevation of temperature caused by the fric- 

 tion of the moving body. At all events, so powerful a friction 

 or compression (as Chladni afterwards assumed, instead of the 

 mere friction, as the cause of the increase of temperature) could 

 only begin in the lowest, densest, but also least considerable 

 portion of the earth's atmosphere. But that such is not the case 

 in this lower region, is proved by the circumstance, that the 

 evolution of light has always ceased when the meteoric mass ar- 

 rives at the lower part of the atmosphere, and also by our per- 

 ceiving this phenomenon of light and fire in the falling bodies 

 at the height of some miles from the earth's surface. 



Secondly, The falling meteoric mass arrives at the earth's 

 surface in a compact state, not melted, not softened, not even, 

 or at least only extremely rarely, red hot ; for its form acquires, 

 by its fall on the ground, no such alteration as would be the 

 consequence of the violent concussion of a soft body against a 

 hard one ; and we have almost no instance of meteoric stones in- 

 flaming, or even burning much, the substances on which they 

 had fallen. Chladni,* among several cases in which damage 

 was caused by meteoric stones, instances only a few in which the 

 injury was produced by the objects being net on fire by such 

 bodies ; and in some of these few examples it is doubtful if 

 the meteoric phenomenon was an aerolite or an ordinary stroke 

 of lightning. If the elevated temperature of meteoric masses 

 Feuermeteorc," p. 77-80. 



VOL. XXII. NO. XL1V. APRIL 1837- U 



