allowed to flow over the excessive hot iron would flash into
steam, and might cause an explosion.

Q. Why do boilers sometimes explode just on the point of
starting the engine?
A. Because starting the engine has the same effect as
opening the safety valve.

Q. Are there any circumstances under which an engineer is
justified in allowing the water to get low?
A. No.

Q. Why do they sometimes do it?
A. From carelessness or ignorance.

Q. May not an engineer be deceived in the gauge of water?
A. Yes.

Q. Is he to be blamed under such circumstances?
A. Yes.

Q. Why?
A. Because if he is deceived by it it shows he has neglected
something.

Q. What is meant by "Priming."
A. It is the passing of water in visible quantities into the
cylinder with the steam.

Q. What would you consider the first duty of an engineer on
discovering that the water was foaming or priming
A. Open the cylinder cocks at once, and throttle the steam.

Q. Why would you do this?
A. Open the cocks to enable the water to escape, and throttle
the steam so that the water would settle.

Q. Is foaming the same as priming?
A. Yes and no.

Q. How do you make that out?
A. A boiler may foam without priming, but it can't prime
without first foaming..

Q. Where will you first discover that the water is foaming?
A. It will appear in the glass gauge, the glass will have a
milky appearance and the water will seem to be running down
from the top, There will be a snapping or cracking in the
cylinder as quick as priming begins.

Q. What causes a boiler to foam?
A. There are a number of causes. It may come from faulty
construction of boiler; it may have insufficient steam room. It
may be, and usually is, from the use of bad water, muddy or
stagnant water, or water containing any soapy substance.

Q. What would you do after being bothered in this way?
A. Clean out the-boiler and get better water if possible.

Q. How would you manage your pumps while the water was
foaming.
A. Keep them running full.

Q. Why?
A. In order to make up for the extra amount of water going
out with the steam.

Q. What is "cushion?"
A. Cushion is steam retained or admitted in front of the
piston head at the finish of stroke, or when the engine is on
"center."

Q. What is it for?
A. It helps to overcome the "inertia" and momentum of the
reciprocating parts of the engine, and enables the engine to
pass the center without a jar.