128 ELECTRICAL ADVANCE IN THE PAST TEN YEARS. 



alternating current possessed the advantage of readily permitting the 

 sending oat over a long distance of a high-j)ressure current with but 

 little loss and by means of comparatively small and inexpensive lines. 

 This current, relatively dangerous, could then be exchanged for a safe 

 low-pressure current on the house mains for working the lights. 



The device which makes the exchange is called a transformer. It 

 is in reality a modified induction coil — a simple structure of copper 

 wire, sheet iron, and insulating materials, with no moving parts to need 

 attention or to get out of order. The i)roperties and use of the trans- 

 former in an alternating-current system were comparatively unknown 

 before 1887, but since that time it has played a part in electric develop- 

 ment the importance of which can not easily be overestimated. It has 

 been, furthermore, brought to a high degree of perfection by the per- 

 sistent and j)ainstaking effort of numerous workers. 



In transforming a current of high pressure to one of lower pressure, 

 or the reverse, only a very slight loss of power or energy is suffered. 

 On a large scale, this loss is barely 3 xier cent of the energy of the 

 transformed current. The larger sizes of transformers now in use 

 have capacities equivalent to considerably over 1,000 horsepower. 

 Some of these structures are employed at Niagara and others at 

 Buffalo. 



As in the case of the apparatus just mentioned, the effort spent in 

 the i)erfection of the huge dynamo electric generators used in lighting 

 and power stations has resulted in machines so perfect as to leave but 

 little chance of further increase of effectiveness. They waste only a 

 small percentage in converting mechanical power into electrical energy, 

 and run for years with but little attention or need of repairs. 



Along with all this improvement has gone a like betterment in the 

 thousand and one details and minor devices which go to make up an 

 electric system. Both incandescent lamps and arc lamps are not only 

 much improved, but, also, their cost is greatly reduced by the use of 

 special machinery and processes of manufacture. Wires, insulating 

 materials, switches, etc., are all far in advance of what they were a few 

 years ago. Safety is secured by many ingenious devices, and the 

 methods of operating have been made far more effective. 



It can not, with truth, be said that electrical arts or industries are 

 still in their infancy, if we are to judge by the perfection of electric 

 manufactures. It has been many years since electrical work could in 

 any sense be regarded as empirical, except by the uninformed. Few of 

 the older arts have possessed or do possess the means for such exact 

 measurement or research; few, indeed, are based upon simi)ler laws of 

 action. Had it been otherwise, the rapid progress whicli has character- 

 ized the past twenty years would have been impossible. 



A striking feature of electrical energy is that it may be readily 

 applied to widely varied work. 



A few instances of this may be given: The large electric-lighting 



