measuring the horse-power of an engine; make yourself so familiar with
it that you could figure any engine without referring to the book. Don't
stop at this, learn to figure the heating surface in any boiler. It
will enable you to satisfy yourself whether you are working your boiler
or engine too hard or what it ought to be capable of doing.

SOME THINGS TO KNOW

Q. What is fire?
A. Fire is the rapid combustion or consuming of organic
matter.

Q. What is water?
A. Water is a compound of oxygen and hydrogen. In weight
88 9-I0 parts oxygen to II I-I0 hydrogen. It has its maximum
density at 39 degrees Fahr., changes to steam at 2I2 degrees,
and to ice at 32 degrees.

Q. What is smoke?
A. It is unconsumed carbon finely divided escaping into
open air.

Q. Is excessive smoke a waste of fuel?
A. Yes.

Q. How will you prevent it
A. Keep a thin fire, and admit cold air sufficient to insure
perfect combustion.

Q. What is low water as applied to a boiler?