THE EFFECTS OF LIGHTNING. 63 



THE EFFECTS OF LIGHTIIIG. 



THE effects which have been observed to attend the transmission of light- 

 ning through bodies which it strikes are so various, and apparently unconnected, 

 that any classification of them is extremely difficult. I shall here adopt that 

 which M. ARAGO has given. The chief effects of lightning may, then, be enu- 

 merated as follows : 



1 . The diffusion of smoke occasionally, and a sulphureous odor almost inva- 

 riably. 



2. The production of chemical changes in the atmosphere itself, and in sub- 

 stances suspended in it. 



3. The fusion of metals, and sometimes the contraction of their dimensions 

 without fusion. 



4. The vitrifications of earthy substances, and the formation of fulgurites, 

 or thunder-tubes. 



5. Mechanical effects in piercing, splitting, and transporting from place to 

 place, the parts of bodies which it strikes. 



6. The production of magnetic effects. 



7. It passes along certain substances in preference to others, and in general 

 its effects are dependant on the nature of the bodies it strikes. 



8. The existence of a storm in the atmosphere is accompanied by a state of 

 the surface of the earth beneath it in which lightning issues upward from it, 

 and objects upon it are struck from below. 



9. Luminous rain. 



10. Rain, snow, and hail, falling in a storm, sometimes emit light when the 

 drops strike each other, or strike the earth. 



We shall consider these classes of effects in succession. 



I. THE SULPHUREOUS ODOR DEVELOPED BY LIGHTNING. 



The following instances have been collected by M. Arago : 



In a thunder-storm on the isthmus of Darien, Wafer, a surgeon, observed 



