37. Q. What is the purpose of a netting in a smoke-box or front end?

A. To act as a crusher of all cinders and prevent large cinders from
passing out of the front end to the atmosphere.

38. Q. What is the object of hollow staybolts?

A. To indicate when the staybolt is broken by the escape of steam
through the small hole in the bolt.

39. Q. What will cause the engine to tear holes in the fire?

A. Working hard or slipping when the dampers are open and the door
closed, or too thin a fire.

40. Q. Name the various adjustable appliances in the front end by which
the draft may be regulated.

A. The exhaust nozzle, the diaphragm and the draft pipes or petticoat
pipe.

41. Q. What object is there in having the exhaust steam go through the
stack?

A. To create a draft through the tubes and fire-box.

42. Q. How does this affect the fire?

A. The exhaust steam escaping through the stack tends to empty the
smoke-box of gases and produces a partial vacuum there, atmospheric