The steam engine familiarly explained and illustrated; with an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain maxims for railway speculators. By the Rev. Dionysius Lardner ... With additions and notes by James Renwick ...

EXPANSION AND -ONDENSATION. 287
third of a foot, which is equivalent to the third of a ton
raised through one foot.
By pursuing like reasoning, it will appear that, if the
direct force of high-pressure steam be combined with the
indirect force produced by its condensation, the total mechanical effect will be precisely equal to the mechanical
effect by the mere condensation of atmospheric steam.
(134.) In applying the principle of expansion to the direct
action of high-pressure steam, advantages are gained analogous to those already explained with reference to the method
of condensation.
Let the piston be supposed to be loaded with three tons;
the evaporation of the water beneath it will raise this weight,
including the atmospheric pressure, through three perpendicular inches. Let one ton be now removed, and the remaining two tons will be raised, by the expansion of the steam,
through another perpendicular inch. Let the second ton
be now removed, and the piston loaded with the remaining
ton will rise, by the expansion of the steam, to the height
of six inches from the bottom. These consequences follow
immediately from the principle that steam will expand in
proportion as the pressure upon it is diminished, observing
that in this case the atmospheric pressure, amounting to one
ton, must always be added to the load. In this process
three separate effects are produced: one ton is raised through
three inches, which is equivalent to a quarter of a ton raised
through one foot; another ton is raised through four inches,
which is equivalent to a third of a ton through a foot, and
the third ton is raised through six inches, which is equivalent
to half a ton raised through a foot. The total of these effects
amounts to one and one-twelfth of a ton raised through one
foot, while the same load, raised by the high-pressure steam
without expansion, would be equivalent to only half a ton
raised through one foot.
Again, let the load placed upon the piston be five tons
the evaporation of the water will raise this through the sixtlh