_Answer._--Newcomen and his partner Cawly adopted a working beam, that
is, a beam working on a centre or trunnion. At one end of the beam was
the pump, at the other was an iron cylinder with an iron piston in it;
both ends of the beam were arched or sexton-shaped, and had a chain on
each, one connected to the pump rod, the other to the piston rod. When
about to start work, the piston being up near the top of the cylinder,
steam was let in under it and a jet of water was let in which soon
condensed the steam and created a vacuum within the cylinder, and the
piston was drawn down to the bottom and the pump drawn up with its load
of water; and a counter weight was attached to the pump-rod to always
bring the piston to the top of the cylinder after each descent. This is
a very brief description of this atmospheric engine; there were now only
two cocks to open and close--the steam cock and water cock, and the
engine only required a boy for this purpose, but the boy himself added a
share in this engine. In order to have a relief from the monotony of
opening and shutting the cocks alternately, he tied strings to the
handles and then connected to the working beam in such a manner that the
cocks were opened and closed exactly at the nick of time; this caused
the engine to work far more regularly and to do twice the work it had
done previously, the boy's name was Humphrey Potter.
40. _Question._--What did James Watt do in connection with the
atmospheric engine?
_Answer._--Watt being a mathematical instrument maker, was requested to
repair an old engine used by some students of Glasgow University; having
finished the repairs, and in working this model (the best type of the
atmospheric engine), he found and proved by many and various
experiments, that an enormous waste of fuel was absolutely necessary in
working the engine; he found great difficulty in keeping the air from
entering the cylinder, and the cylinder top was so exposed to the
atmosphere that the steam was much condensed when it entered the
cylinder, and he came to the conclusion to put a cover on the top of the
cylinder, and allow the piston-rod to play in a hole in the cover with a
gland and stuffing box, and _to press down the piston with steam instead
of the atmosphere_. This engine was no longer atmospheric, it was a real
steam engine, the first ever seen or constructed, for steam was used to
create the vacuum, and steam was used to work the piston; but this was
only the beginning of his great improvements. This engine though
suitable for the purpose of pumping water, was totally unsuitable for
continuous rotary motion, the steam acting only on the downward stroke
after the piston had been pulled up to the top of the cylinder by means
of the additional weight fixed on the pump end of the beam. He devised a
method to admit steam under the piston as well as above it, but the
flexible chains although suitable for the down stroke of the piston were
powerless in the up stroke, they would hang listless and useless. This
being so, he determined to get rid of the chains at both ends of the
beam, and also both arched ends, and substitute a ridged connection at
both ends of the beam. He put an iron connecting rod from the end of the
beam to the pump rod, and the other end of the beam was connected to the
piston rod by a crosshead; to this engine he attached that grand
appendage the "Parallel Motion" which is the pride of the beam engine up
to to-day. He devised the improvement of the separate condenser for the
exhaust steam, instead of the jet of water under the piston. He invented
the crank for his engine, also the sun and planet motion, also the
throttle valve, also the counter to indicate the number of revolutions
the engine had performed, also the "Cut off," the steam moving the
piston by expansion when it was cut off at one-third the length of the
cylinder, and thus saving two-thirds of the steam and a more uniform
rate of speed.
41. _Question._--Give a description of the Sun and Planet method, and
why he invented it?
_Answer._--The sun and planet were two cog-wheels geared into each
other, the sun being 3 feet diameter and the planet 2 feet diameter, the
latter was keyed tightly on the bottom end of the connecting rod, and
the sun which was keyed tightly on the end of the shaft, that was to
revolve and work the machinery. But although this method did make the
machinery revolve, it was not smoothly, for when the planet wheel was at
either top or bottom of the sun wheel, the power of the engine was less
effective than it was half way in the opposite positions. This led Watt
to add a large wheel on the shaft of the sun wheel, called the fly
wheel, which equalised the rate of motion to uniformity. Watt invented
the crank for his engine, but one of his men gave the tip to an engineer
at Bristol, who forthwith took out a patent for it and forestalled Watt,
who had to invent another means--the sun and planet. But when the term
of the patent expired, Watt resumed the crank method instead of the sun
and planet, which was noisy, the wear and tear very great, and also
expensive.
42. _Question._--What other things did Watt do towards the perfection of
the steam engine?
_Answer._--He added the air pump to his engine to draw the condensed
steam and water from his separate condenser; he invented the throttle
valve and the governor, in order to sustain a uniform rate of speed in
the engine, whatever pressure of steam might be on, or variation of
work, whether heavy or light.