The Three Secretaries 139 



upon the principle of reciprocating polarity of soft iron by 

 electro-dynamic agency." l 



Henry's oscillating machine was the forerunner of all our 

 modern electrical motors. The rotary motor of to-day is the 

 direct outgrowth of his improvement in magnets. 



It should also be stated that he had as early as 1832, or 

 before, applied one of his great magnets to the separation of 

 magnetic iron from other substances, and in 1833 this system, 

 which has since become one of great industrial importance, 

 was put into actual use at the Penfield Iron-Works, in the 

 village of Port Henry, named at that time in honor of the 

 Albany professor. 



Thomas Davenport, a blacksmith from Salisbury, Vermont, 

 who visited the Port Henry iron-works about this time, 

 bought one of the magnets and used it in the experiments 

 which led not only to the construction by him of the earliest 

 operating rotary motors, but which within two years led 2 to 

 the beginning of the electric railroad; for he exhibited in 

 1835, in Springfield, Troy, and Philadelphia, not only rotary 

 motors in action, but a model engine carrying its own magnet, 

 which ran around upon a circular track. 



Even more significant than the invention of this engine 

 was Henry's philosophic and far-reaching appreciation of 

 what it meant for the future. "So far from giving way to the 

 natural enthusiasm of the successful inventor," writes Pope, 

 " Henry proceeded, with calm sobriety of judgment, to fore- 

 cast the future possibilities of the new motor. He was soon 

 led to see that under the conditions of knowledge then exist- 

 ing, the power could only be derived from the oxidation of 

 zinc in a galvanic battery, and hence the heat energy re- 



1 Joule, James P., "Historical Sketch of the cal, Statistical, and Technical." A paper read 

 Rise and Progress of Electro-magnetic En- before the New York Electric Club, January 

 gines for Propelling Machinery." 22, 1891, by Franklin Leonard Pope. See 



2 " Notes on the Electric Railway: Histori- The Electrical Engineer, January 28, 1891. 



