CHAPTER VI. 



THE ENGINE PROPER. 



HE term "traction engine" commonly includes, 

 not only what is, strictly speaking, the en- 

 gine, but the boiler and traction parts as 

 well. In this book, the term "engine proper" 

 will be used to designate those parts which 

 are actually concerned in converting the 

 energy of steam into rotary motion. The 

 boiler changes water into steam by adding to it, heat, taken 

 from the fuel. The engine proper^ consumes steam and 

 delivers motion. 



FIG. 14. SIDE ELEVATION OF ENGINE PROPER. 



The Cylinder. It is in the cylinder that the actual 

 change of heat into motion takes place. Here the steam 



