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 ...

CHAPTER III.
ENGINES OF SAVERY AND NEWCOMEN.
Savery's Engine.-Boilers and their Appendages.-Working Apparatus.-.
Mode of Operation. —Defects of the Engine.-Newcomen and Cawley.- -
Atmospheric Engine.-Accidental Discovery of Condensation by Jet.Potter's Discovery of the Method of working the Valves
(31.) THE steam engine contrived by Savery, like every
other which has since been constructed, consists of two parts
essentially distinct. The first is that which is employed to
generate the steam, which is called the boiler, and the
second, that in which the steam is applied as a moving
power.
The former apparatus in Savery's engine consists of two
strong boilers, sections of which are represented at D and E
in fig. 7; D the greater boiler, and E the less. The tubes T
and T' communicate with the working apparatus which we
shall presently describe. A thin plate of metal R is applied
closely to the top of the greater boiler D turning on a centre
c, so that by moving a lever applied to the axis c on the
outside of the top, the sliding plate R can be brought from
the mouth of the one tube to the mouth of the other alternately. This sliding valve is called the regulator, since it
is by it that the communications between the boiler and two
steam vessels (hereafter described) are alternately opened and
closed, the lever which effects this being constantly wrought
by the hand of the attendant.
Two gauge pipes are represented at G, G', the use of
which is to determine the depth of water in the boiler.
One G has its lower aperture a little above the proper depth,
and the other G' a little below it. Cocks are attached to the