THE ENGINE PROPER. 63 



63.6174 area of piston in square inches, 



65=(5o% of 130), the "mean effective" pressure 



(pounds per square inch.) 

 3180870 

 3817044 



4135.1310 total average pressure on piston in pounds. 

 416.6 travel of piston in feet per minute. 



24810786 

 24810786 



4I35I3I 

 16540524 



33,000)1722695.5746(52.20 (The "calculated" horse-power correspoiid- 

 165000 ing to the "indicated" horsepower^ 



72695 

 66000 



66955 

 66000 



95574 



Deducting ten per cent, for the friction of the working 

 parts of the engine, we have forty-seven horse-power as the 

 result. This remainder is a little more than three times the 

 rated horse-power and represents the power actually deliv- 

 ered at the engine fly-wheel, and corresponds to the "brake" 

 horse-power. 



Compound Engines. A compound engine is one in which 

 the steam is expanded in two or more cylinders. Threshing 

 engines, when compounded, are "two-cylinder" compounds, 

 but large stationary and marine engines are often "triple" 

 and sometimes "quadruple" expansion. There are different 

 types of two-cylinder compounds, viz. : the "cross," where 



