SCIENCE OF COMMON THINGS. 279 



Principal agents in nature exciting electricity. 



results obtained, however, by the United States Coast 

 Survey, with iron wire, show a velocity of from 15,000 

 to 20,000 miles per second. 



1813 What agents are undoubtedly the most active in producing and 

 exciting electricity in the operations of nature f 



The light and heat of the suds rays. 



1813 It has become the habit with many to ascribe to electricity the 

 agency of phenomena in the natural world, the cause of which may not be 

 apparent: is there any reason for this? 



There certainly is not : electricity is diffused through 

 all matter, and is ever active, and many of its pheno- 

 mena cannot be satisfactorily explained ; but it is go- 

 verned, like all other forces of nature, by certain fixed 

 laws, and it is by no means a necessary agent in all the 

 operations of nature. 



It argues great ignorance to refer without examination every mysteri- 

 ous phenomenon to the influence of electricity. 



1814 Do some animals have the power of exciting electricity within 

 themselves f 



There are certain animals which are gifted with the 

 extraordinary power of producing electncal phenomena 

 by an effort of muscular or nervous energy. Among 

 these the electrical eel and the torpedo are most re- 

 markable. 



1815 How powerful a charge of electricity can the electrical eel send 

 forth when in full vigor f 



Sufficient to knock down a man or stun a horse. 



1810 Is the electricity generated by these animals the same as that occa- 

 sioned by tlie ordinary electrical machine ? 



It is the same, and produces the same effects. 



Do vital action and muscular movements in man and animals 

 give rise to electricity f 



They do ; and it can be shown by direct experiment 

 that a person cannot even contract the muscles of the 

 arm without exciting an electrical action. 



1818 Does change of form or state in bodies generally produce electrical 

 excitation ? 



Change of form or state is one of the most powerful 

 methods of exciting electricity. 



