128 GALVANIC ELECTRICITY. 



dertook to find out the cause. In preparing for the in- 

 vestigation, he chanced to hang the hind legs of seve- 

 ral frogs, by copper hooks, from the iron railing of the 

 balcony of his window. As often as the wind, or any 

 accidental cause, brought the muscles into contact with 

 the iron bar, the legs were convulsively agitated. The 

 astonishment of the experimenter can scarcely be con- 

 ceived. In undertaking to account for an old fact, he 

 had stumbled upon a most important discovery. The 

 theory which he proposed was not correct, but the re- 

 sults to which the observation have since led are as- 

 tounding. The telegraph, the electrotype, and many 

 metals discovered by galvanic means, may all be re- 

 garded as its offspring. 



302. EXPLANATION. The convulsion 



Explain the 



above experi- produced in this case, is entirely analagous, 

 in its course, to that described in the last 

 paragraph. The two metals, the moist muscle, and 

 the wind, to produce contact, and so complete the cir- 

 cuit, are all the conditions essential to the production 

 of a current, and consequent contraction of the nerves. 



