The Supply and Uses of Water 247 



make use of it not only in lighting and heating, but in trans- 

 portation, manufacturing, and communication. To-day, falling 

 water, wherever found, can be harnessed to produce electric 

 energy, which may be transmitted a distance of five hundred 

 miles and then converted into mechanical energy. This dis- 

 tance is only a beginning which the future will greatly extend. 



Transmission of the electric current over long distances by 

 means of a comparatively thin copper or aluminum wire at a 

 relatively small expense is only one of the principal advantages 

 of electricity. To-day electricity is transmitted over distances 

 which a few years ago were considered impossible. The electric 

 energy produced at the hydroelectric plant at Keokuk is 

 transmitted to St. Louis, a distance of 144 miles. The current 

 is carried at 110,000 volts on a five eighth inch copper cable, 

 which is supported on steel towers eighty feet high and eight 

 hundred feet apart. From the power plants at Niagara Falls 

 electricity is transmitted about 160 miles in the United States, 

 at 60,000 voltage, on aluminum wires one and one eighth inches 

 in diameter; and in Canada at 110,000 voltage to more distant 

 points. The Big Creek Power Company in California to-day 

 transmits current with perhaps the highest voltage and over 

 the longest distance. The two power stations, four miles apart, 

 are located abo\it seventy miles from Fresno, at Big Creek 

 (cf. Fig. 69). The electricity is transmitted at 160,000 voltage 

 to Los Angeles, about 240 miles distant. The six cables of 

 aluminum are each one inch in diameter. The power is re- 

 ceived at a sub-station, where it is transformed and distributed 

 for domestic, municipal, transportation, and manufacturing 

 purposes. 



The transfer of electric energy over long distances at un- 

 usually high voltage is made possible by the transformer and 

 the electric switch. At the power station the electric current 

 generated is stepped up or transformed (see page 329) to a very 

 high voltage for long distance transmission. At the receiving 

 station the high voltage is transformed or stepped down to the 



