78 ELECTEIC TRACTION. 



heard of " Barlow's wheel." This was the first elementary- 

 electric motor. He found that by passing a current from the 

 centre to the circumference of a copper disc between the poles 

 of a magnet the disc would revolve. Faraday, you will have 

 observed, in his researches in induction, reversed Barlow's 

 experiment, but those discoveries resulted in the dynamo. It 

 was not until 1873 that the reversibility of the dynamo was 

 discovered, although for many years previous to this motors 

 for driving machinery were operated, but depended on the 

 galvanic battery for a supply of current. This process, being 

 a very limited one, went to the wall when a cheaper current 

 was effected by the discovery of the dynamo. The action of 

 the practical and commercial motor now used is that of a 

 magnet and a wire conveying a current, and is the reverse 

 action of the dynamo, in which the motion of the conductor 

 generates the current. On the other hand, a current in the 

 conductor creates motion. 



The law of the survival of the fittest has been an important 

 factor in reference to types and varieties of the motor, not 

 only in many mechanical appliances, but other resources 

 resorted to to intensify the currents. 



Having, it is hoped, given a clear insight into the theory 

 of these electrical machines it is to be regretted that the 

 limits of this paper will not permit a detailed description of 

 the mechanical parts (Diagram of Sprague's Motor — A) ; but 

 so long as the elementary truths have been retained, and that 

 they will be brought to bear on the more descriptive 

 portions of this paper, the object of the same will have been 

 attained. 



There are two methods of applying electricity for traction 

 purposes — (1) by storage batteries; and (2) by metallic con- 

 ductors over and under the track, known as the " overhead 

 system" and the "underground" system respectively. 

 These methods, however, are both of a direct nature, the 

 motors being supplied with current from the conductors as 

 wanted. As an ideal method of propulsion the storage or 

 accumulator system stands pre-eminently foremost, and the 

 "best electrical intellects of the day are devising and improv- 

 ing with a view to eliminate the many defects which prevent 

 it from being introduced commercially. The batteries occupy 

 but little room, and are placed under the seats, and the motor 

 is placed under the body of the car. There is no smoke or 

 dust or accompanying noise and no street gearing, and the 

 aesthetic sense is greatly conciliated by its attractive and 

 graceful movement without contact. This is all very well on 

 paper, but when brought into actual experience, like all 

 ideals, it falls short of expectation. The serious objections 

 to its commercial employment are that the accumulators are 



