steam engines. It is necessary to
have fuel and water. When fuel is burned, the water coming in contact
with the hot sheets evaporates and becomes steam, which is then used in
the cylinders to force the pistons back and forth.

6. Q. About what quantity of water should be evaporated in a locomotive
boiler to the pound of coal?

A. From five to seven pounds of water. For example, one gallon of water
weighs eight and one-third pounds, therefore 100 pounds of coal should
evaporate from sixty to eighty-four gallons of water.

7. Q. What is steam, and how is it generated?

A. Steam is water in the condition of a vapor and is generated by
heating the water above the boiling point.

8. Q. What is the purpose of the water gauge glass and gauge cocks?

A. To indicate the level of water in the boiler.

9. Q. What would indicate to you that the boiler connections of water
gauge glasses were becoming clogged?

A. The up and down movement of the water in the glass would become slow
and inactive, or it would not register correctly with the gauge cocks.

10. Q. At what temperature does water boil?

A. At atmospheric pressure, which is 14.7 pounds at sea level, water
boils at 212 degrees Fahrenheit; the temperature, however, increases as
the pressure under which the water is boiled increases. At 200 pounds
boiler pressure the temperature would be 388 degrees Fahrenheit.

11. Q. What is carbon?

A. Carbon forms the greatest part of all kinds of coal; the higher the
per cent. of carbon, the higher the grade of coal.

12. Q. What is the composition of bituminous coal?

A. It is composed of carbon about 75 per cent. and many gaseous
substances, as is shown by its burning with a large flame and much
smoke. Anthracite, on the contrary, is nearly pure carbon and burns with
a small flame.

13. Q. What is combustion?

A. Combustion or burning is a chemical process, it is the action of fire
on inflammable substances and is the union of the oxygen in the air with
the carbon in the fuel; this is called rapid combustion. Slow combustion
is the decaying of wood or iron by the elements.

14. Q. Is air necessary for combustion?

A. Yes.

15. Q. About how many cubic feet of air is necessary for the combustion
of a pound of coal in a locomotive fire-box?

A. About 300 cubic feet of air must pass through the grates and fire
for complete combustion of one pound of coal.

16. Q. Why must air be heated before combining with coal?