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XLIV. On the Origin of Meleorlc Stones. 



To Mr. Tilhch. 



Sir,- M. La Place with many other philosophers have been 

 of opinion tliat meteoric stones were masses ejected froin the 

 moon; and the chief objections urged against this theory are, 

 that tlieir appearance is invariably attended with a swift hori- 

 zontal motion and violent explosion. But if it can be proved that 

 under certain circumstances these effects must necessarily fol- 

 low, the theory uill receive an interesting and material corro- 

 boration. These stones, it is well known, are composed almost 

 entirely of silicia, ma!?nesia, oxide of iron and nickel, partly me- 

 tallic and partly oxidized. Now modern discoveries have proved 

 silex to be an oxide formed by an unknown infiammable base 

 which by its extreme aviditv for osv^en becomes instantaneously 

 saturated with it. Sir H. Davy has demonstrated that magnesia 

 is also a metallic oxide, and not without great difficulty separable 

 from its base. Respecting nickel and iron, we know that the 

 former can only be oxidized, and then but slovvly, by exposure to 

 atmospheric air at an intense heat, and that the latter becomes 

 more or less oxidized according to its ciuaiitv and degree ot 

 exposure to air. -in 



Here then we have a solid body composed of materials aH 

 susceptible of oxygenation, and in that state in which we might 

 naturally expect to find them if, previously existing in their on- 

 o-inal purity, they had been suddenly exposed to the action of 

 oxygen. In addition to these, let us suppose the admission of 

 -any of the alkaline metals. What would be the result it a mass 

 thus composed were to be thrown from the moon with a force 

 sufficient to come within the range of the earth's attraction?— It 

 would be precisely that which is experienced in the case of a 

 fall of aerolites. ' The body would pursue its rapid course, and 

 by the laws of motion be partly impelled in an horizontal direc- 

 tion. On apnroaching our atmosphere the effect upon the com- 

 ponent molecule would be immediate. The unknown inflain- 

 mable base of silex would absorb its oxygen, and appear in the 

 state in which it now exists. A similar effect would be expe- 

 rienced by the magnesium, which would become magnesia. The 

 nickel would from its partial affinity for oxygen be only jjartly 

 oxidized by the heat evolved during the detonation ot the alka- 

 line metals, «nd the iron be so in rather a stronger degree, and 

 chiefly on its external surface where it is most exposed, which 

 we find to be the case. The alkaline metals would rapidly com- 

 bine with oxygen ; and as heat would naturally be increased by 

 the velocity of motion, a violent explosion attended with brilliant 

 Q 3 fla"»e 



