Fig. 16 is a longitudinal section of a boiler of the drop flue variety. For
land purposes the lowest range of tubes is generally omitted, and the smoke
makes a last return beneath the bottom of the boiler.

Figs. 17 and 18 are the transverse and longitudinal sections of a tubular
boiler, built in 1837 by R.L. Stevens for the steamboat Independence.

[Illustration: Fig. 16.]

[Illustration: Fig. 17.]

[Illustration: Fig. 18.]

Fig. 19 is a longitudinal section of a common wood-burning locomotive.

[Illustration: Fig. 19.]




THE ENGINE.

93. _Q._--The steam passes from the boiler through, the steam pipe into the
cylinder of the engine?

_A._--And presses up and down the piston alternately, being admitted
alternately above and below the piston by suitable valves provided for that
purpose.

94. _Q._--This reciprocating motion is all that is required in a pumping