NATURAL PHILOSOPHY. 171 



tortuous course along the trunk. It is not to he supposed, how- 

 ever, that the electric induction, and the tension caused by it, 

 which precede discharge, exist only along the line of violent 

 action. 



The line of discharge may be considered the resultant of the 

 electric tension for some distance around, and along this line is 

 experienced, at the moment, all the accumulated force from induc- 

 tive action. 



The violently disruptive effects which sometimes occur, are 

 adequately explained by the heat produced along the line of dis- 

 charge. 



No other known agency generates heat so suddenly and of such 

 intensity as the electric force. The reason is plain. The electric 

 force, being itself molecular, develops, or, as some would prefer, 

 is converted into heat at the same instant throughout the whole 

 body, and its explosive power is exerted simultaneously between 

 all the particles, and needs no transfer by conduction. The vio- 

 lence with which some chemical compounds explode is propor- 

 tional, other things being equal, to the consentaneousness of the 

 action among the particles. 



Allowing the velocity of electricity to be the same as that of 

 light, the time in which a coin or metallic bullion on the person 

 would be melted is inconceivably short, less than the twelve- 

 billionth part of a second. The same explosive action expended 

 on the air causes the terrific sound of thunder, Near the path of 

 discharge, it is a crash, sharp, spiteful. At a distance, it is toned 

 down by the elasticity of the air into a roar which shakes the very 

 earth. It seems strange that some writers should attribute the 

 sound to the collapse ; it is but the reaction from the condensed 

 air around the line of displacement, and of course cannot exceed 

 the force of displacement. The latter, then, is the primary cause 

 of the sound ; the collapse only repeats the undulation with some 

 loss of force. 



Surprise is sometimes expressed that the human body, when 

 struck, is not torn or burned. The electricity is a good deal dif- 

 fused through so large and so good a conductor, but the textnre 

 of the body is of such a nature, composed of porous, elastic 

 solids filled with liquids, that its particles readily yield to the re- 

 quirements of the force without disruption. 



The mechanical, and perhaps chemical, disttn-bances on the 

 nervous system, even if there be no other, are quite sufficient to 

 account for the fatal efi"ects of the electric shock. The experience 

 of the writer was, that a discharge from a battery of 12 jars of 1 

 gallon each, passed through the length of the body, is best ex- 

 pressed by the phrase, " a stunning blow." 



If these general laws be correct, precautions for safety should 

 conform to them. A lightning-rod is intended to afford a ready 

 passage between the clond tmd earth to any electricity whicli 

 may be accumulating. If it discharges the electricity as fast as it 

 is generated, then there can be no collection in quantity or inten- 

 sity sufficient to cause violence. The rod is a good conductor; 

 that is, its particles readily assume the conditions required for 



