808 The Outline of Science 



In America great stretches of main lines have been elec- 

 trified and are worked by electric passenger and freight locomo- 

 tives, of up to 4,000 horse-power. The feats performed by some 

 of these monsters in mountainous districts are indeed astonishing. 

 On the Norfolk and Western Railway coal trains of 3,250 tons 

 are taken up 2 per cent, grades by two electric haulers at double 

 the speed previously attained by three of the largest Mallet steam 

 locomotives. This is but one instance out of many that could be 

 quoted. The secret of the electric locomotive's colossal strength 

 is of course that a very much larger percentage of its total weight 

 can be devoted to the apparatus that gives rotation to its wheels, 

 since it draws its energy from an outside source instead of from 

 a ponderous boiler. 



Climbing the Rocky Mountains 



The longest stretches of main line yet electrified are on the 

 Chicago, Milwaukee and St. Paul Railway, the most recently 

 completed of the "Transcontinentals." One of these, the Rocky 

 Mountains section, is 440 miles long; and the other, the Cascade 

 Mountains section, from Othello to Tacoma, 211 miles long. The 

 gap of 200 miles on the flatter country between them will in due 

 course be electrified also, and a continuous run of over 800 miles 

 by electric power be possible. These sections include many long and 

 severe grades, sharp curves, and many tunnels, and generally taxed 

 steam traction to the utmost, especially in winter, when the steam 

 trains were liable to get frozen up during enforced halts. Running 

 times have been cut down by one-third since electrification. 



The sections are supplied by several power-houses with cur- 

 rent transmitted as alternating current at 100,000 to 110,000 

 volts to sub-stations distributed at intervals of about 30 miles 

 along the line, where it is stepped-down and converted into 3,000- 

 volt direct current for feeding to the overhead conductors. The 

 same general principles are adopted for most electrified railways, 

 though the pressures and distances may be different. 



