Steam, Its Generation and Use | Page 4

and engine design of Smeaton, Newcomen
and their contemporaries, were followed by those of the great engineer,
James Watt, an instrument maker of Glasgow. In 1763, while repairing
a model of Newcomen's engine, he was impressed by the great waste of
steam to which the alternating cooling and heating of the engine gave
rise. His remedy was the maintaining of the cylinder as hot as the
entering steam and with this in view he added a vessel separate from
the cylinder, into which the steam should pass from the cylinder and be
there condensed either by the application of cold water outside or by a
jet from within. To preserve a vacuum in his condenser, he added an air
pump which should serve to remove the water of condensation and air
brought in with the injection water or due to leakage. As the cylinder
no longer acted as a condenser, he could maintain it at a high
temperature by covering it with non-conducting material and, in
particular, by the use of a steam jacket. Further and with the same
object in view, he covered the top of the cylinder and introduced steam
above the piston to do the work previously accomplished by
atmospheric pressure. After several trials with an experimental
apparatus based on these ideas, Watt patented his improvements in
1769. Aside from their historical importance, Watt's improvements, as
described in his specification, are to this day a statement of the
principles which guide the scientific development of the steam engine.
His words are:

"My method of lessening the consumption of steam, and consequently
fuel, in fire engines, consists of the following principles:
"First, That vessel in which the powers of steam are to be employed to
work the engine, which is called the cylinder in common fire engines,
and which I call the steam vessel, must, during the whole time the
engine is at work, be kept as hot as the steam that enters it; first, by
enclosing it in a case of wood, or any other materials that transmit heat
slowly; secondly, by surrounding it with steam or other heated bodies;
and, thirdly, by suffering neither water nor any other substance colder
than the steam to enter or touch it during that time.
"Secondly, In engines that are to be worked wholly or partially by
condensation of steam, the steam is to be condensed in vessels distinct
from the steam vessels or cylinders, although occasionally
communicating with them; these vessels I call condensers; and, whilst
the engines are working, these condensers ought at least to be kept as
cold as the air in the neighborhood of the engines, by application of
water or other cold bodies.
"Thirdly, Whatever air or other elastic vapor is not condensed by the
cold of the condenser, and may impede the working of the engine, is to
be drawn out of the steam vessels or condensers by means of pumps,
wrought by the engines themselves, or otherwise.
"Fourthly, I intend in many cases to employ the expansive force of
steam to press on the pistons, or whatever may be used instead of them,
in the same manner in which the pressure of the atmosphere is now
employed in common fire engines. In cases where cold water cannot be
had in plenty, the engines may be wrought by this force of steam only,
by discharging the steam into the air after it has done its office....
"Sixthly, I intend in some cases to apply a degree of cold not capable of
reducing the steam to water, but of contracting it considerably, so that
the engines shall be worked by the alternate expansion and contraction
of the steam.
"Lastly, Instead of using water to render the pistons and other parts of

the engine air and steam tight, I employ oils, wax, resinous bodies, fat
of animals, quick-silver and other metals in their fluid state."
The fifth claim was for a rotary engine, and need not be quoted here.
The early efforts of Watt are typical of those of the poor inventor
struggling with insufficient resources to gain recognition and it was not
until he became associated with the wealthy manufacturer, Mattheu
Boulton of Birmingham, that he met with the success upon which his
present fame is based. In partnership with Boulton, the business of the
manufacture and the sale of his engines were highly successful in spite
of vigorous attacks on the validity of his patents.
Though the fourth claim of Watt's patent describes a non-condensing
engine which would require high pressures, his aversion to such
practice was strong. Notwithstanding his entire knowledge of the
advantages through added expansion under high pressure, he continued
to use pressures not above 7 pounds per square inch above the
atmosphere. To overcome such pressures, his boilers were fed through
a