A. Free movement of the water, so that it may come in contact with the
heating surface and after being converted into steam be immediately
replaced by a fresh supply of water.
30. Q. What would be the effect if a "leg" of the fire-box became filled
with mud?
A. There would be no water in contact with the fire-box sheets and they
would quickly become overheated and mud-burned.
31. Q. What would be the result if the fire-box sheets became
overheated?
A. They would be weakened and forced off the staybolts and an explosion
would occur.
32. Q. Would it be advisable to put water into a boiler after the sheets
had become bare and red hot?
A. No. The fire should be killed at once.