CURRENTS 



1675 



CURTISS 



on insulators most of the current would flow 

 to the ground along the poles and be lost. 

 Sometimes wires carrying the current for oper- 

 ating electric motors, as on street car lines, 

 are incased in rubber to prevent loss by the 

 air, which at all times takes some energy from 

 the conductor. 



According to the method of generating them 

 electric currents are of two classes, direct and 

 .alternating. 



Direct Current. A direct current is one that 

 flows continuously in the same direction, like 

 that produced by an electric battery. The 

 direct current is used for ringing electric bells, 

 in experiments in the laboratory and in oper- 

 ating electric motors where great power is 

 required in starting and frequent variation of 

 speed is necessary, as on electric cars. 



Alternating Current. An alternating current 

 is one whose direction is rapidly reversed by 

 the use of a magnet. If a magnet is placed in 

 a coil of wire along which an electric current 

 is flowing, the current is reversed. When the 

 magnet is withdrawn, the current again flows 

 in its original direction. The same effect is 

 produced whether a permanent or an electric 

 magnet is used. Many devices have been in- 

 vented for the purpose of reversing the current, 

 but the one in most common use is the revolv- 

 ing electromagnet which causes the reversal 

 by reversing its poles. The alternating current 

 is used for electric lighting and for electric 

 motors where a uniform rate of speed is re- 

 quired. See ELECTRICITY; ELECTROMAGNET; 

 ELECTROMAGNETISM ; ELECTRIC MOTOR. 



CURRENTS, OCEAN. See OCEAN CURRENTS. 



CURTIS, GEORGE WILLIAM (1824-1892), an 

 American essayist, editor and lecturer who was 

 one of the best-loved and most highly-re- 

 spected public men of his time. He was born 

 in Providence, R. I. At the age of eighteen 

 he found himself interested in the Transcen- 

 dental movement (see TRANSCENDENTALISM), 

 and for two years lived at Brook Farm (which 

 see). After spending a few years in European 

 and Eastern travel, Curtis returned home in 

 1850 and began a brilliant career in New York 

 City. He became associate editor of Putnam's 

 Magazine, and for this periodical and for 

 Harper's Monthly wrote a large number of 

 essays that at once struck the popular fancy. 

 The most important collections of his essays 

 are the Potiphar Papers, gently satirizing the 

 fashionable society of his time, and Prue and I, 

 a study of life in which humor, tenderness 

 and sentiment are pleasingly blended. "The 



Editor's Easy Chair," which he created for 

 Harper's Monthly, was for years one of the 

 most popular departments of that periodical. 



Curtis became political editor of Harper's 

 Weekly in 1863, and made that journal a 

 powerful force in shaping public opinion during 

 the War of Secession and after its close. He 

 was one of the founders of the Republican 

 party and one of its most influential leaders 

 until 1884, when he became an independent in 

 politics. In the advancement of civil service 

 reform he was long a conspicuous figure, and 

 the report which he wrote as chairman of the 

 civil service commission, in 1871, has been the 

 basis of later efforts to extend and purify the 

 service. 



CURTISS, GLENN HAMMOND (1878- ),the 

 inventor of the flying boat, an American whose 



CURTISS'S "FLYING TROPHY" 



Neptune and Mercury hailing the airship sail- 

 ing above the clouds. 



name stands next to that of the Wright 

 brothers in the list of famous contributors to 

 the science of air navigation (see FLYING MA- 

 CHINE). He holds many patents for biplane 



