Transportation on Water 



365 



ocean liners have been equipped with highly developed tur- 

 bines and reciprocating engines, a combination yielding greater 

 power without increase in consumption of fuel. 



Advantages of the steam turbine. The reciprocating engine, 

 with back and forth stroke of the piston, stopping momentarily 

 at every stroke, produces a continual jar- 

 ring when operating at high speed. The 

 vibration of the express ocean liners 

 became more and more intolerable as their 

 triple or quadruple expansion engines were 

 driven hard to reduce the time required 

 for crossing the ocean. The jarring was 

 reduced somewhat by certain improve- 

 ments. Meanwhile the steam turbine 

 proved its value and either supplemented 

 or replaced the reciprocating engine. The 

 turbine is noiseless, free from vibration, 

 steady, of comparatively small size and 

 weight, and of tremendous power produc- 

 tion with consequently greatly increased 

 possibilities of speed. As to weight and 

 power production, an old low-pressure 

 engine produces about two horse power 

 for each ton of machinery; the turbine 

 produces more than six horse power for 

 each ton. The turbine is also more efficient than the best 

 type of reciprocating engine ; and it is more flexible in con- 

 struction, adaptable to high and low pressure, thus taking from 

 steam all its energy. 



One great steamship with quadruple screw has six turbines 

 adapted to high and low pressure of steam. Steam is admitted 

 to the first series at a pressure of 210 pounds to the square inch 

 (see table, page 312). It is conducted from these to the low 

 pressure turbines and then into condensers. The turbines de- 

 velop about 70,000 horse power and make possible a speed of 



FIG. 129. Principle 

 of the steam turbine, 

 as illustrated in Hero's 

 steam engine (about 120 

 B.C.). 



