A. They are riveted to a wrought iron ring called a mud-ring.
25. Q. Describe the ash-pan and its use.
A. It is a receptacle secured to the fire-box and usually provided with dampers to regulate the flow of air to the fire. It collects the ashes that drop from the fire-box and prevents them from setting fire to bridges or other property along the track. Engine-men must know that ash-pan slide and hopper bottoms are closed before leaving enginehouse.
26. Q. What is a "wagon-top" boiler?
A. It is a boiler that has the fire-box end made larger than the cylindrical part to provide more steam space.
27. Q. Why are boilers provided with steam domes?
A. To furnish more steam space and to obtain dryer steam and to provide a place for the safety valves, steam pipes, throttle valve and whistle.
28. Q. What must be the condition of a boiler to give the best results?
A. It must have good circulation and be clean and free from mud or scale.
29. Q. What is meant by "circulation" in a boiler?