IX 



MAN'S NEWEST CO-LABORER: THE DYNAMO 



AS you stand waiting for your train at elevated or 

 subway station you must have noticed the third 

 rail. To outward appearance it is not different 

 from the other rails. It seems a mere inert piece of steel. 

 Yet you are well aware that a strange power abides 

 there unseen a power that pulls the train, and that 

 lurks in hiding to strike a death-blow to any chance un- 

 fortunate whose foot or hand comes in contact with 

 the rail. As the heavy train dashes up, dragged by this 

 unseen power, probably you, in common with the rest of 

 the world, have been led to remark, "Is it not marvel- 

 ous?" 



Marvelous it surely seems. Yet the cause of our as- 

 tonishment is to be sought in the relative newness of the 

 phenomena rather than in the nature of the phenomena 

 themselves. At first glance it may seem that the in- 

 tangible character of the electrical power gives it a 

 unique claim on our wonderment. But a moment's 

 reflection dispels this illusion. After all, electricity 

 is no more intangible than heat. Neither the one nor the 

 other can be seen or heard, but each alike may be felt. 

 Yet we observe without astonishment a locomotive 

 propelled by the power of heat simply because the 

 locomotive has become an old story. Again, electricity 



