366 



Introduction to the Study of Science 



more than twenty-six knots, equivalent to about thirty miles an 

 hour. Another liner may be taken as a type of the combina- 

 tion of reciprocating engines and turbines of low pressure (Fig. 

 130). The engines are of the quadruple expansion type, and 

 utilize the steam at an initial pressure of 215 pounds per square 

 inch. The steam performs work in the reciprocating engines 



FIG. 130. A rotor of a low pressure turbine of a great ocean liner. The 

 diameter is 18 feet. 



until it has about nine pounds pressure per square inch. Then 

 it is conducted to the turbines, where it expands until it has a 

 pressure of one pound per square inch (Fig. 131). The tur- 

 bines develop 16,000 horse power, which with the 30,000 horse, 

 power produced by the reciprocating engines gives a speed of 

 approximately twenty-two knots. 



Turbines are employed to supplement reciprocating engines 

 not only on steamships but also in stationary power plants, 

 such as the subway power plant of New York City. The 



