M. Arago on Lightning. 85 



tions of ponderable substances strongly impregnated with the 

 very essence of the thunderbolt. How, then, are these conglo- 

 merations formed ? in what regions are they produced ? whence 

 do they obtain the substances which compose them ? what is 

 their nature ? and why are they sometimes suspended for a 

 long period, only that they may precipitate themselves with the 

 greater rapidity ? &c. &c. To all tliese inquiries, science re- 

 mains mute, and can make no reply. 



Lightning, in traversing the atmosphere, effects here and 

 there the combination of its two gaseous elements, and trans- 

 forms them into nitric acid. Is it then impossible that the same 

 action may sometimes instantaneously produce a kind of semi- 

 union of all the different kinds of matter which exist in a given 

 volume of air ? If this conjecture, which I do not offer in a 

 detailed form, but express with all ])ossible brevity, should ap- 

 pear to be inadmissible, I may mention that M. Fusinieri states, 

 tliat he has constantly found metallic iron — iron in different 

 degrees of oxidation — and sulphur, in the powdery deposits 

 which surround the fissures through which the thunderbolt 

 has passed. Without having tjie slightest wish to revive anti- 

 quated ideas regarding thunder-stones^^ I shall simply remark 

 here, that it is not proved that we should absolutely regard as 

 false the whole of the narratives, in which a fall of various 

 matters is related to have accompanied thunder storms. What 

 pretext, for example, is there for considering as untrue the fol- 



'^ The pretended thunder-stones which some nations venerated, had ge- 

 lu'iiilly the form of a wedge, an axe, or of tlie iron point of an arrow 

 or lance. The origin of these stones is not at all doubtful, since precisely 

 similar ones have been found among the tools and arms of the natives of 

 America, and since we have learned how they are made. The ancient Con- 

 tinent, also, was originally inhabited by savage nations ; and similar rc- 

 (juirements, and a similar scarcity of ii-on, would produce in it the same 

 kind of industry. But when the improvement in metallurgy produced 

 stronger instruments, more cutting and more convenient, stones were aban- 

 doned, and have since been preserved uninjured below the surface of the 

 ground. These stones have often been found in the trunks of trees, and 

 hence it has been contended that they owed their position there to a thun- 

 der storm — every other explanation was held to be an impossibility. But, 

 at this rate, it must have been thunder which introduced toads into the 

 trunks of those trees where they are concealed, and the several pieces of 

 ancient money which the hatchet is frequently revealing. 



