THE EVOLUTION OF THE DYNAMO. 



Fig. i. A small example of the original commercial form of the drum armature ma- 

 chine, patented in 1873 by Dr. Werner Siemens and F. Von Hefner Alteneck. The armature 

 is a development of the Siemens shuttle form of 1856, and gives a nearly continuous current. 

 An early experimental dynamo. Fig. 3. Ferranti's original dynamo, patented in 

 2-1883. The field magnets are stationary and consist of two sets of electro-magnets each 

 r ith 1 6 projecting pull pieces, between which the armature revolves. Fig. 4. The gigantic 

 rotary converters of the Manhattan Elevated Railway. 



