THE EFFECTS OF LIGHTNING. 



65 



II. CHEMICAL CHANGES OPERATED BY LIGHTNING. 



The experiment formerly alluded to, in which, by transmitting the electric 

 spark through atmospheric air confined in a glass tube, a combination took 

 place between a portion of its constituents and liquid nitric acid was formed, 

 was due to the celebrated Cavendish. After the identity of lightning and elec- 

 tricity was established, no doubt was entertained that the same process took 

 place in the atmosphere whenever lightning was transmitted through it. The 

 direct demonstration of this important fact was made by Professor Liebig in 

 1827. 



That philosopher submitted seventy-seven samples of rain-water, collected ! 

 on different occasions, to the process of slow distillation. Of these samples, 

 seventeen were collected during or immediately after thunder-storms. In the 

 residue obtained from these seventeen, nitric acid was found in greater or less 

 quantities, in combination with lime, or with ammonia. In fifty-eight of the 

 other samples, these substances were not found ; and in the remaining two, 

 mere traces of nitric acid were just discoverable. 



The formation of nitric acid in the atmosphere during thunder-storms sug- 

 gests to philosophical observers various important objects of attention and 

 inquiry. Under what circumstances of season, locality, height, and tempera- 

 ture, of the clouds, does the quantity of nitric acid thus formed vary ? In tropi- 

 cal regions, where thunder-storms are phenomena of daily occurrence for entire 

 months, is the quantity of nitric acid generated in the air sufficient to feed the 

 natural veins of nitre found in certain localities where the absence of animal 

 matter has rendered such formations a matter of great theoretical difficulty 1 

 The researches may also lead to the solution of the origin of the other sub- 

 stances, such as lime and ammonia, detected by Liebig in the pluvial waters 

 falling from stormy clouds, and possibly for the sulphureous gas, of which the 

 odor is so remarkable in places where lightning penetrates. 



It would be a curious and interesting result of scientific investigation to 

 demonstrate that the thunder of heaven elaborates in the clouds the chief in- 

 gredient of the counterfeit thunder which man has invented for the destruction 

 of his fellows. 



III. THE FUSION AND CONTRACTION OF METALS. 



The power of lightning to effect the fusion of metals was observed by the 

 ancients. Aristotle, Lucretius, Seneca, and Pliny, mention this property, but 

 in a manner and attended by circumstances which, in the judgment of many, 

 cast doubts on the truth of their statements. Aristotle mentions the copper on 

 a shield being fused by lightning, while the wood which it covered was unin- 

 jured. Seneca states that the coin contained in a purse was fused, while the 

 purse was unchanged ; that a sword was liquefied, while the scabbard in whicl 

 it lay was untouched ; and that the iron points of spears being melted, flowed 

 along the wood to which they were attached without burning it. Pliny relates 

 that coins of gold, silver, and copper, sealed up in a bag, were melted by light- 

 ning, the bag not being burnt, nor the wax which sealed it softened. 



If the fusion or liquefaction here referred to were understood to mean the 

 complete fusion of the various pieces of metal mentioned by these several wri- 

 ters, there would be undoubtedly great difficulty in reconciling their statements 

 with the known properties of matter. But if, on the other hand, partial or su- 

 perficial fusion be meant, the well-ascertained results of modern observation 

 corroborate this ancient evidence. 



In 1781, M. D'Aussac and the horse on which he was mounted were killed 

 VOL,. II. 5 



