

PREFACE 



To a good many of us the inventor is the true 

 hero for he multiplies the working value of 

 life. He performs an old task with new econ- 

 omy, as when he devises a mowing-machine to 

 oust the scythe ; or he creates -a service wholly 

 new, as when he bids a landscape depict itself on 

 a photographic plate. He, and his twin brother, 

 the discoverer, have eyes to read a lesson that 

 Nature has held for ages under the undiscerning 

 gaze of other men. Where an ordinary observer 

 sees, or thinks he sees, diversity, a Franklin de- 

 tects identity, as in the famous experiment here 

 recounted which proves lightning to be one and 

 the same with a charge of the Ley den jar. Of a 

 later day than Franklin, advantaged therefor 

 by new knowledge and better opportunities for 

 experiment, stood Faraday, the founder of 

 modern electric art. His work gave the world the 

 dynamo and motor, the transmission of giant 

 powers, almost without toll, for two hundred 

 miles at a bound. It is, however, in the carriage 

 of but trifling quantities of motion, just enough 

 for signals, that electricity thus far has done its 

 most telling work. Among the men who have 

 created the electric telegraph Joseph Henry has 

 a commanding place. A short account of what 

 he did, told in his own words, is here presented. 

 Then follows a narrative of the difficult task of 



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