THE CONQUEST OF NATURE 



It appears, then, that the phenomena of the electric 

 dynamo depend upon the curious relations that exist 

 between magnetism and electricity. Granted the es- 

 sential facts of magneto-electric induction, all the phe- 

 nomena of the dynamo are explicable. But how ex- 

 plain these facts themselves ? Why is an electric current 

 generated in a coil of wire moving in a magnetic field ? 

 And why is a wire carrying a current of electricity, when 

 placed across a magnetic field, impelled to move at 

 right angles to the lines of magnetic force ? No thought- 

 ful person can consider the subject without asking these 

 questions. But as yet no definitive answer is forthcom- 

 ing. Some suggestive half-explanations, based on an 

 assumed condition of torsion or strain in the ether, have 

 been attempted, but they can hardly be called more 

 than scientific guesses. 



Meanwhile, it may be understood that the mutual 

 relations of the magnetic and electrical forces just 

 referred to are not at all dependent upon the manner 

 in which the electric current is generated. The magneto- 

 electric motor may be operated as well with a chemical 

 battery as with such a mechanical generating dynamo 

 as has just been described. The storage-batteries 

 which have been employed in some street railways and 

 those which propel the electric cabs about our city 

 streets furnish cases in point. The only reason these 

 are not more generally employed is that the storage 

 battery has not yet been perfected so that it can produce 

 a large supply of electricity in proportion to its weight, 

 and produce it economically. 



[182] 



