In the chronology of the steam-engine, the contemporaries of Watt have
been so completely overshadowed by the greater and more successful
inventor, as to have been almost forgotten by the biographer and by
the student of history. Yet, among the engineers and engine-builders,
as well as among the inventors of his day, Watt found many
enterprising rivals and keen competitors. Some of these men, had they
not been so completely fettered by Watt's patents, would have probably
done work which would have entitled them to far higher honor than has
been accorded them.
WILLIAM MURDOCH was one of the men to whom Watt, no less than the
world, was greatly indebted. For many years he was the assistant,
friend, and coadjutor of Watt; and it is to his ingenuity that we are
to give credit for not only many independent inventions, but also for
the suggestions and improvements which were often indispensable to the
formation and perfection of some of Watt's own inventions.
Murdoch was employed by Boulton & Watt in 1776, and was made
superintendent of construction in the engine department, and given
general charge of the erection of engines. He was sent into Cornwall,
and spent in that district much of the time during which he served the
firm, erecting pumping-engines, the construction of which for so many
years constituted a large part of the business of the Soho
establishment. He was looked upon by both Boulton and Watt as a
sincere friend, as well as a loyal adherent, and from 1810 to 1830 was
given a partner's share of the income of the firm, and a salary of
L1,000. He retired from business at the last of the two dates named,
and, dying in 1839, was buried near the two partners in Handsworth
Church.
Murdoch made a model, in 1784, of the locomotive patented by Watt in
that year. He devised the arrangement of "sun-and-planet wheels,"
adopted for a time in all of Watt's "rotative" engines, and invented
the oscillating steam-engine (Fig. 36) in 1785, using the "D-slide
valves," _G_, moved by the gear, _E_, which was driven by an eccentric
on the shaft, without regard to the oscillation of the cylinder, _A_.
He was the inventor of a rotary engine and of many minor machines for
special purposes, and of many machine-tools used at Soho in building
engines and machines. He seems, like Watt, to have had special
fondness for the worm-gear, and introduced it wherever it could
properly take the place of ordinary gearing. Some of the machines
designed by Watt and Murdoch, who always worked well together, were
found still in use and in good working condition by the author when
visiting the works at Soho in 1873. The old mint in which, from 1797
to 1805, Boulton had coined 4,000 tons of copper, had then been pulled
down, and a new mint had been erected in 1860. Many old machines
still remained about the establishment as souvenirs of the three great
mechanics.
[Illustration: FIG. 36.--Murdoch's Oscillating Engine, 1785.]
Outside of Soho, Murdoch also found ample employment for his inventive
talent. In 1792, while at Redruth, his residence before finally
returning to Soho, he was led to speculate upon the possibility of
utilizing the illuminating qualities of coal-gas, and, convinced of
its practicability, he laid the subject before the Royal Society in
1808, and was awarded the Rumford gold medal. He had, ten years
earlier, lighted a part of the Soho works with coal-gas, and in 1803
Watt authorized him to extend his pipes throughout all the buildings.
Several manufacturers promptly introduced the new light, and its use
extended very rapidly.
Still another of Murdoch's favorite schemes was the transmission of
power by the use of compressed air. He drove the pattern-shop engine
at Soho by means of air from the blowing-engine in the foundery, and
erected a pneumatic lift to elevate castings from the foundery-floor
to the canal-bank. He made a steam-gun, introduced the heating of
buildings by the circulation of hot water, and invented the method of
transmitting packages through tubes by the impulse of compressed air,
as now practised by the "pneumatic dispatch" companies. He died at the
age of eighty-five years.
Among the most active and formidable of Watt's business rivals was
JONATHAN HORNBLOWER, the patentee of the "compound" or double-cylinder
engine. A sketch of this engine, as patented by Hornblower in 1781, is
here given (Fig. 37). It was first described by the inventor in the
"Encyclopaedia Britannica." It consists, as is seen by reference to the
engraving, of two steam-cylinders, _A_ and _B_--_A_ being the low and
_B_ the high pressure cylinder--the steam leaving the latter being
exhausted into the former, and, after doing its work there, passing
into the condenser, as already described. The piston-rods, _C_ and
_D_, are both connected to the same part of the beam by chains, as in
the other early engines. These rods pass through stuffing-boxes in the
cylinder-heads, which are fitted up like those seen on the Watt
engine. Steam is led to the engine through the pipe, _G Y_, and cocks,
_a_, _b_, _c_, and _d_, are adjustable, as required, to lead steam
into and from the cylinders, and are moved by the plug-rod, _W_, which
actuates handles not shown. _K_ is the exhaust-pipe leading to the
condenser. _V_ is the engine feed-pump rod, and _X_ the great rod
carrying the pump-buckets at the bottom of the shaft.
The cocks _c_ and _a_ being open and _b_ and _d_ shut, the steam
passes from the boiler into the upper part of the steam-cylinder, _B_;
and the communication between the lower part of _B_ and the top of _A_
is also open. Before starting, steam being shut off from the engine,
the great weight of the pump-rod, _X_, causes that end of the beam to
preponderate, the pistons standing, as shown, at the top of their
respective steam-cylinders.
The engine being freed from all air by opening all the valves and
permitting the steam to drive it through the engine and out of the
condenser through the "snifting-valve," _O_, the valves _b_ and _d_
are closed, and the cock in the exhaust-pipe opened.
[Illustration: FIG. 37.--Hornblower's Compound Engine, 1781.]
The steam beneath the piston of the large cylinder is immediately
condensed, and the pressure on the upper side of that piston causes it
to descend, carrying that end of the beam with it, and raising the
opposite end with the pump-rods and their attachments. At the same
time, the steam from the lower end of the small high-pressure cylinder
being let into the upper end of the larger cylinder, the completion of
the stroke finds a cylinder full of steam transferred from the one to
the other with corresponding increase of volume and decrease of
pressure. While expanding and diminishing in pressure as it passes
from the smaller into the larger cylinder, this charge of steam
gradually resists less and less the pressure of the steam from the
boiler on the upper side of the piston of the small cylinder, _B_, and
the net result is the movement of the engine by pressures exerted on
the upper sides of both pistons and against pressures of less
intensity on the under sides of both. The pressures in the lower part
of the small cylinder, in the upper part of the large cylinder, and in
the communicating passage, are evidently all equal at any given time.
When the pistons have reached the bottoms of their respective
cylinders, the valves at the top of the small cylinder, _B_, and at
the bottom of the large cylinder, _A_, are closed, and the valves _c_
and _d_ are opened. Steam from the boiler now enters beneath the
piston of the small cylinder; the steam in the larger cylinder is
exhausted into the condenser, and the steam already in the small
cylinder passes over into the large cylinder, following up the piston
as it rises.
Thus, at each stroke a small cylinder full of steam is taken from the
boiler, and the same weight, occupying the volume of the larger
cylinder, is exhausted into the condenser from the latter cylinder.
Referring to the method of operation of this engine, Prof. Robison
demonstrated that the effect produced was the same as in Watt's
single-cylinder engine--a fact which is comprehended in the law
enunciated many years later by Rankine, that, "so far as the
theoretical action of the steam on the piston is concerned, it is
immaterial whether the expansion takes place in one cylinder, or in
two or more cylinders." It was found, in practice, that the Hornblower
engine was no more economical than the Watt engine; and that erected
at the Tin Croft Mine, Cornwall, in 1792, did even less work with the
same fuel than the Watt engines.
Hornblower was prosecuted by Boulton & Watt for infringement. The suit
was decided against him, and he was imprisoned in default of payment
of the royalty, and fine demanded. He died a disappointed and
impoverished man. The plan thus unsuccessfully introduced by
Hornblower was subsequently modified and adopted by others among the
contemporaries of Watt; and, with higher steam and the use of the Watt
condenser, the "compound" gradually became a standard type of
steam-engine.
Arthur Woolf, in 1804, re-introduced the Hornblower or Falck engine,
with its two steam-cylinders, using steam of higher tension. His first
engine was built for a brewery in London, and a considerable number
were subsequently made. Woolf expanded his steam from six to nine
times, and the pumping-engines built from his plans were said to have
raised about 40,000,000 pounds one foot high per bushel of coals, when
the Watt engine was raising but little more than 30,000,000. In one
case, a duty of 57,000,000 was claimed.
The most successful of those competitors of Watt who endeavored to
devise a peculiar form of pumping-engine, which should have the
efficiency of that of Boulton & Watt, and the necessary advantage in
first cost, were WILLIAM BULL and RICHARD TREVITHICK.[42] The
accompanying illustration shows the design, which was then known as
the "Bull Cornish Engine."
[42] For an exceedingly interesting and very faithful account of
their work, _see_ "Life of Richard Trevithick," by F. Trevithick,
London, 1872.
[Illustration: FIG. 88.--Bull's Pumping-Engine, 1798.]
The steam-cylinder, _a_, is carried on wooden beams, _b_, extending
across the engine-house directly over the pump-well. The piston-rod,
_c_, is secured to the pump-rods, _d d_, the cylinder being inverted,
and the pumps, _e_, in the shaft, _f_, are thus operated without the
intervention of the beam invariably seen in Watt's engines. A
connecting-rod, _g_, attached to the pump-rod and to the end of a
balance-beam, _h_, operates the latter, and is counterbalanced by a
weight, _i_. The rod, _j_, serves both as a plug-rod and as an
air-pump connecting-rod. A snifting-valve, _k_, opens when the engine
is blown through, and relieves the condenser and air-pump, _l_, of all
air. The rod, _m_, operates a solid air-pump piston, the valves of the
pump being placed on either side at the base, instead of in the
pump-bucket, as in Watt's engines. The condensing-water cistern was a
wooden tank, _n_. A jet "pipe-condenser," _o_, was used instead of a
jet condenser of the form adopted by other makers, and was supplied
with water through the cock, _p_. The plug-rod, _q_, as it rises and
falls with the pump-rods and balance-beam, operates the
"gear-handles," _r r_, and opens and closes the valves, _s s_, at the
required points in the stroke. The attendant works these valves by
hand, in starting, from the floor, _t_. The operation of the engine is
similar to that of a Watt engine. It is still in use, with a few
modifications and improvements, and is a very economical and durable
machine. It has not been as generally adopted, however, as it would
probably have been had not the legal proscription of Watt's patents so
seriously interfered with its introduction. Its simplicity and
lightness are decided advantages, and its designers are entitled to
great credit for their boldness and ingenuity, as displayed in their
application of the minor devices which distinguish the engine. The
design is probably to be credited to Bull originally; but Trevithick
built some of these engines, and is supposed to have greatly improved
them while working with Edward Bull, the son of the inventor, William
Bull. One of these engines was erected by them at the Herland Mine,
Cornwall, in 1798, which had a steam-cylinder 60 inches in diameter,
and was built on the plan just described.
Another of the contemporaries of James Watt was a clergyman, EDWARD
CARTWRIGHT, the distinguished inventor of the power-loom, and of the
first machine ever used in combing wool, who revived Watt's plan of
surface-condensation in a somewhat modified form. Watt had made a
"pipe-condenser," similar in plan to those now often used, but
had simply immersed it in a tank of water, instead of in a
constantly-flowing stream. Cartwright proposed to use two concentric
cylinders or spheres, between which the steam entered when exhausted
from the cylinder of the engine, and was condensed by contact with
the metal surfaces. Cold water within the smaller and surrounding the
exterior vessel kept the metal cold, and absorbed the heat discharged
by the condensing vapor.
Cartwright's engine is best described in the _Philosophical Magazine_
of June, 1798, from which the accompanying sketch is copied.
[Illustration: FIG. 39.--Cartwright's Engine, 1798.]
The object of the inventor is stated to have been to remedy the
defects of the Watt engine--imperfect vacuum, friction, and
complication.
In the figure, the steam-cylinder takes steam through the pipe, _B_.
The piston, _R_, has a rod extending downward to the smaller
pump-piston, _G_, and upward to the cross-head, which, in turn, drives
the cranks above, by means of connecting-rods. The shafts thus turned
are connected by a pair of gears, _M L_, of which one drives a pinion
on the shaft of the fly-wheel. _D_ is the exhaust-pipe leading to the
condenser, _F_; and the pump, _G_, removes the air and water of
condensation, forcing it into the hot-well, _H_, whence it is returned
to the boiler through the pipe, _I_. A float in _H_ adjusts an
air-valve, so as to keep a supply of air in the chamber, to serve as a
cushion and to make an air-chamber of the reservoir, and permits the
excess to escape. The large tank contains the water supplied for
condensing the steam.
The piston, _R_, is made of metal, and is packed with two sets of cut
metal rings, forced out against the sides of the cylinder by steel
springs, the rings being cut at three points in the circumference, and
kept in place by the springs. The arrangement of the two cranks, with
their shafts and gears, is intended to supersede Watt's plan for
securing a perfectly rectilinear movement of the head of the
piston-rod, without friction.
In the accounts given of this engine, great stress is laid upon the
supposed important advantage here offered, by the introduction of the
surface-condenser, of permitting the employment of a working-fluid
other than steam--as, for example, alcohol, which is too valuable to
be lost. It was proposed to use the engine in connection with a still,
and thus to effect great economy by making the fuel do double duty.
The only part of the plan which proved both novel and valuable was the
metallic packing and piston, which has not yet been superseded. The
engine itself never came into use.
At this point, the history of the steam-engine becomes the story of
its applications in several different directions, the most important
of which are the raising of water--which had hitherto been its only
application--the locomotive-engine, the driving of mill-machinery, and
steam-navigation.
Here we take leave of James Watt and of his contemporaries, of the
former of whom a French author[43] says: "The part which he played in
the mechanical applications of the power of steam can only be compared
to that of Newton in astronomy and of Shakespeare in poetry." Since
the time of Watt, improvements have been made principally in matters
of mere detail, and in the extension of the range of application of
the steam-engine.
[43] Bataille. "Traite des Machines a Vapeur," Paris, 1847.
[Illustration]