OPERATION OP ENGINE. 



fore two hundred times in passing over a mile. The speed of sixty 

 miles an hour is that of a mile per minute. The driving wheels 

 will, therefore, revolve two hundred times per minute. But it 



Ffc. 11. 



w 



has heen already explained that to produce one revolution of the 

 wheels each piston is moved once backwards and forwards in each 

 cylinder, and each cylinder must be twice filled with steam from 



K2 131 



