ELECTEICITY DURING THE NINETEENTH CENTURY. 345 



lamps and groups of lumps, meters for measuring the consumption of 

 electric energy were wanted, safety fuses and cut-offs had to be pro- 

 vided, electroliers, or fixtures, to support the lamps were required, and 

 lastly, a complete system of underground mains with appurtenances 

 was a requisite for city plants. 



Even the steam engines for driving the dynamos had to be remodeled 

 and improved for electric work, and ten years of electric lighting 

 development did more toward the refinement and perfection of steam 

 engines than fift}" years preceding. Steadiness of lights meant the 

 preservation of steady speed in the driving machinery. The Pearl 

 Street station, in New York City, was the first installation for the 

 supply of current for incandescent lighting in a city district. The 

 constant-pressure dynamos were gradually improved and enlarged. 

 The details of all parts of the system were made more perfect, and in 

 the hands of Edison and others the incandescent lamps, originally of 

 high cost, were much cheapened and the quality of the production 

 was greatly improved. Lamps originally cost |1 each. The best 

 lamps that are made can be had at present for about one-fifth that 

 price. Millions of incandescent lamps are annually manufactured. 

 Great lighting stations furnish the current for the working of these 

 lamps, some stations containing machinery aggregating many thou- 

 sands of horsepower capacit3^ Not only do these stations furnish 

 electric energy for the working of arc lamps and incandescent lamps, 

 but in addition for innumerable motors ranging in size from the small 

 desk fan of one-tenth horsepower up to those of hundreds of horse- 

 power. The larger sizes replace steam or hydraulic power for elevators, 

 and many are used in shops or factories for driving machinery, such 

 as printing presses, machinery tools, and the like. 



In spite of the fact that it was well known that a good dynamo when 

 reversed could be made a source of power, few electric motors were 

 in use until a considerable time after the establishment of the first 

 lighting stations. Even in 1884, at the Philadelphia Electrical Exhi- 

 bition, only a few electric motors were shown. Not until 1886 or 

 thereafter did the "motor load" of an electric station begin to be a 

 factor in its business success. The motors supplied are an advanta- 

 geous adjunct, inasmuch as they provide a day load, increasing the out- 

 put of the station at a time when the lighting load is small and when 

 the machinery in consequence would, without them, have to remain 

 idle. The growth of the application of electric motors in the closing 

 years of the century has been phenomenal, even leaving out of consid- 

 eration their use in electric railways. 



Twenty years ago an electric motor was a curiosity; fifty years ago 

 crude examples run by batteries were only to be occasionally found m 

 cabinets of scientific apparatus. Machinery Hall at the Centennial 

 Exhibition of 1876 typified the mill of the past, never again to be 



