350 ELECTRICITY DURING THE NINETEENTH CENTURY. 



embodied in itself the latest results of American practice, was also 

 maniifaotured in America to suit the needs of the road. Other similar 

 railways are in contemplation in London and in other cities of Eui'ope. 

 As on the elevated roads in New York City, the replacement of 

 mulerground steam traction, where it exists, by electric traction is 

 e\idently only a (juestion of a few years. 



An electric railway may exemplify a power transmission system in 

 which power is delivered to moving vehicl(>s. But the distances so 

 covered are not generally more than a few miles from the oenerating 

 station. AVhcre, however, abundant water power exists, as at Niag- 

 ara, or where fuel is very expensive and power is to be had only at 

 great distances from the place at which it is to ])e used, electricity fur- 

 nishes the most etlective means for transmission and distribution. 

 Betw(M'n the years ISSO and ISDO th(» d(^vici» called the alternating cur- 

 rent ti'ansformer was developed to a considerable degree of })erfection. 

 It is in reality a modified induction coil, consisting of copper wire and 

 iron, whereby a current sent through one of its coils will induce simi- 

 lar currents in the other coils of apparatus. It has the great advan- 

 tage of having no moving i)ai"ts. Faraday, in 1831, discovered the 

 fundamental principle of the modei'ii transformer. Not only, how- 

 ever, will tiie current in one coil of the apparatus generate by induc- 

 tion a new current in an entirely separate coil or circuit, but b}' 

 suitably proportioning the windings we may exchange, as it were, a 

 large low-pressure current for a small l)ut high-pressure current, or 

 vice versa. This exchange may be made with a very small percentage 

 of loss of energy. These valuable properties of the transformer have 

 rendered it of supreme importance in recent electrical extension. The 

 first use made of it, in 1885-86, was to transform a high-pressure cur- 

 rent into one of low pressure in electric lighting, enabling a small wire 

 to be used to convey electric energy at high pressure and without 

 much loss to a long distance from the station. This energy at high 

 pressure reaches the transformer placed within or close to the building 

 to be lighted. A low-pressure safe current is conveyed from the 

 transformer to the wires connected to the lamps. In this way a cur- 

 rent of 2,000 volts, an unsafe and unsuita))le pressure for incandescent 

 lighting, is exchanged for one of about 100 volts, which is quite safe. 

 In this wa}^ also the suppl}^ station is enabled to reach a customer too 

 far away to be supplied directly with current at 100 volts without enor- 

 mous expense for copper conductors. 



The alternating current transformer not onl}^ greatly extended the 

 radius of supply from a single station, but also enabled the station to 

 be conveniently located where water and coal could be had without 

 difficulty. It also permitted the distant water powers to become 

 sources of electric energy for lighting, power, or for other service. 

 For example, a water power located at a distance of 50 to 100 miles or 



