Popular Science Monthly 



869 



this switchboard, is a panel carrying 300 

 signal lamps and a. duplicate set of tele- 

 phone terminals. When a feeder is in 

 operation a green lamp shows. This is re- 

 placed by a red lamp when the feeder is not 

 in operation. This 

 makes the location of 

 any trouble in the 

 system an easy mat- 

 ter. 



The field frame of 

 these gigantic genera- 

 tors is twenty-one 

 feet high and twenty- 

 six feet across the 

 supporting legs. The 

 weight of each com- 

 plete generator is 105 

 tons. Five tons of 

 copper are used in its 

 ccnstruction. Owing 

 to their immense size, 

 it was necessary to 

 construct these gener- 

 ators in parts, for the 

 height of the arma- 

 ture alone is greater than the clearance on 

 most railroads at bridges and tunnels. To 

 transport the parts of each generator from 

 Ampere, N. J., to Detroit, Mich., required 

 four freight cars. 



Each generator develops 3,750 kilowatts 

 at an electrical pressure of 250 volts and 80 

 revolutions per minute. This quantity of 

 electrical energy would light 150,000 25- 

 watt lamps, or 7,500 arc lamps. It is 

 equivalent to 5,000 horsepower and the out- 

 put of a single generator 

 would be sufficient to run 

 300 street cars. Each gener- 

 ator supplies continuously 

 15,000 amperes of current. 

 The whole plant supplies 

 260,000 amperes. The 

 total output is one-eight 

 eth of the potential ca 

 pacity of Niagara. 



These generators are 

 driven by fourteen 

 6000-horsepower and 

 one 4000-horsepower 

 reciprocating engines 

 of the gas-steam type 

 and one 1500 horse- 

 power straight steam 

 engine, all of which are 

 direct-connected to the 

 shafts of the genera- 

 tors. The water used 



Here you get an idea of the size of the gen- 

 erator by a simple comparison of the 

 field casting with a four-passenger Ford car 



in cooling cylinders, pistons, valve boxes 

 and bearings of the gas unit leaves the 

 engine at a temperature of 175 degrees 

 Fahrenheit and is utilized for boiler feed 

 and hot water factory supply. The exhaust 

 gases, at a tempera- 

 ture of 1 1 00 degrees 

 Fahrenheit are em- 

 ployed to maintain 

 the temperature of 

 the steam between 

 the high and low 

 pressure cylinders of 

 the steam engines, 

 after which it pre- 

 heats the boiler feed 

 water. The steam 

 engines are of the 

 double expansion 

 Gorliss type. The 

 boilers contain 1800 

 tubes having an ap- 

 proximate heating 

 surface of 26,000 

 square feet. 



Germany's spike-studded boards which 

 were left all along the roads when 

 the Hindenburg Line retreated. They 

 were intended to cripple the pursuing 

 Allies but they were discovered in time 



One of the Ways the Retreating Ger- 

 man Army Tried to Prevent Pursuit 



WHEN the Germans made what has be- 

 come known as the strategic retreat 

 of the Hindenburg Line they very naturally 

 wanted to prevent the Allies from following 

 them too closely. Various obstacles were 

 put in the path of the 

 pursuers. Those which 

 they counted on to 

 make the most trouble 

 for their enemies were 

 huge spiked boards, 

 shown in the accom- 

 panying illustration. 



These wicked-look- 

 ing boards were placed 

 all along the roads and 

 in the trenches. They 

 are constructed of 

 heavy planks thickly 

 studded with spikes. 

 These were covered 

 over with brush, leaves, 

 branches of trees or 

 any other available 

 "camouflaging" device 

 which might be de- 

 pended upon to con- 

 ceal the obstruction 

 from the rapidly ad- 

 vancing troops. 



