3.  Q. What pressure is indicated by the steam gauge?  What is meant by atmospheric pressure?

A. The pressure per square inch inside of the boiler.  Atmospheric pressure is the pressure represented by the density of the atmosphere in pounds per square inch, which is at sea level 14.7 pounds.

4.  Q. On what principle does a steam gauge work?

A. The steam gauge pointer is actuated by a flattened or bent round tube to straighten itself under the pressure of steam against the water inside of tube.  The gauge pointer receives movement from suitable mechanism connected with the tube.

5.  Q. What is the source of power in a steam locomotive?

A. Heat is the source of power in all 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.