The picture here given is a modern and highly Ornamented reproduction
of Hero's machine, which is earliest shown in Stuart's "History of
the Steam Engine," 1829, and reproduced by the author in later publications.
Curiously enough, this little machine, which has often been reproduced,
unwittingly, by modern inventors, and actually used with a fair degree of
satisfaction, illustrates a form of engine which is " theoretically,"
ideally perfect. Its operation under the theoretically best conditions,
assuming it made with similar perfection and to be free from frictionwastes,
would give highest possible efficiency and economy in the use of steam.
But this would involve its operation at inapproachable velocities and the
impracticable condition of being frictionless; nevertheless, it is perfectly
possible to secure such favourable conditions in practice as will make a
fairly economical machine, when placed in comparison with the forms of engine
which modem invention has produced. Its action is simple and easily seen.
Steam is made in the boiler which forms its base, and passes up through
one or both of the hollow supporting columns or pipes, entering the axis
of the whirling globe, filling it at a pressure determined by the rate at
which steam is formed; and it is then expanded, finally issuing from the
projecting arms or ajutages, and by its reaction turning the globe with
considerable force and at high speed. Modern engines of this construction
have been used quite successfully in driving factories and mills, and have
been found to use no very extravagant amount of steam; but have finally
been thrown out, on account, mainly.
Of their cost for repairs; the whirling arms being usually rapidly cut away
by their swift passage through the steamladen atmosphere in which they necessarily
work. Ideally, the machine is an "expansion engine" of the most
perfect type.
From the days of Hero, however, nothing more is heard of the use of steam
in any apparatus, nor is any machine produced capable of doing work in that
manner. All through the early and the middle ages the force of confined
steam and other vapours is evidently known, but no attempt that may be regarded
as at all serious was made to utilize its latent power. Little " Eeolipiles"-
vessels in which steam was produced and from which it issued in a jet which
was sometimes employed to cause an induced current of air with which to
blow the fire-were the only steam engines, until, about the sixteenth century,
it seems to have been suspected by one or another of the woolgathering philosophers
and the plodding mechanics of those days that steam had a somewhat higher
mission. At about the end of that century and the beginning of the seventeenth,
we find records of various contrivances, in the application of steam to
useful purposes, which indicate that at last the minds of men were awakening
to the consideration of the problem of the centuries. These inventions,
if it can be said, fairly, that they were inventions, were commonly directed
to the application of the force of confined steam to the raising of water
through considerable heights, as in the draining of mines, or in furnishing
a housesupply. Da Porta, in 1601, De Caus in 1605 to 1615, and Branca, 1629,
were among those who began to suggest, rather than to practise, the application
of steam to useful work. The first two pictured contrivances for raising
water, which were, however, but distant imitations of the notions of Hero;
while the lastnamed gave drawings, with some elaboration, of machines, by
the action of steamjets, usually impinging against vanes, driving mills
and metallurgical machinery. At about the latter time, the second Marquis
of Worcester began his now famous career of invention, and probably as early
as 1630 had devised what is known as his "engine" or his "fireengine,"
a machine, however, which was really but the Hero fountain on an enlarged
and somewhat more practically available scale, and in better form. He did
apply it to its purpose of raising water, though; and this constitutes for
him a legitimate and sufficient claim for remembrance and honour. He was
the first to use steam-so far as is positively known- for industrial ends.
It is known that he was engaged in erecting an engine at least as early
as 1648, but his patents were only issued in 1663. It seems very certain
that the marquis built two or more of these " fireengines; " but
their exact form is unknown, and it is only certain that he profited nothing
by his ingenuity and enterprise. He finally died unsuccessful and in comparative
poverty. His widow was as unhappy and unfortunate as her husband, and died
in 1881 without having gained a foothold for her spouse's invention.
The death of this truly great man, inventor and statesman as he was, in
the highest sense, did not, however, put an end to the progress which he
had initiated. His friend and successor in this work, Sir Samuel Morland,
made himself thoroughly familiar with the subject, secured opportunities
to construct a number of such engines, and became so well informed as to
their capabilities that he published an account of the apparatus, in which
paper he introduced tables of the number and sizes of the working cylinders
required to raise given quantities of water to specified heights in stated
times; thus, for the first time, constructing the now usual specifications
for use in determining the requirements of purchasers. Yet neither the machines
of Worcester nor those of Morland became generally used. These men were
in advance of their time; and it was only when, some years later, Captain
Savery,- a man of talent both as an engineer and a man of business, whose
character united all the elements of success in practical operations,-took
up the task that it became in any degree a commercial success. Very little
is known in detail of the experiments or of the constructions of the Marquis
of Worcester; and that absorbing romance by George Macdonald, "St.
George and St. Michael," may perhaps be taken as quite as authoritative
as any biography, so far as such minor details are concerned; but the work
of Savery, nearly a halfcentury later, came within the range of modern history,
and is well understood.
When Savery took up the new problem, at the opening of the eighteenth century,
the mines of Great Britain had become, in many instances, so deep that the
labour of freeing them from water was an enormously difficult and expensive
task with the means and apparatus at the disposition of the mineowners.
They had rude forms of pump worked by horsepower almost exclusively; and
in the older and more extensive mines, hundreds of horses were sometimes
kept at work, and the profits of mining were becoming daily less and less,
and seemed likely to be soon extinguished by this great tax on production.
Worcester and his contemporaries had seen this threatening outlook, and
were apprehend e that Britain might soon lose that supremacy, industrially,
which she had, in consequence of her success in mining, up to chat time
so firmly held. They had, in many cases, looked to steam or some as yet
undiscovered motor to do this work more cheaply than horsepower; but even
Worcester and Morland failed to make practically useful application of the
new "fire engine." Savery, familiar with the business of mining,
a mechanic by experience and practice as well as by nature, not only saw
the opportunity, but saw also a way to secure a prize. He made a workmanlike
reproduction of the Worcester machine, giving it a form capable of immediate
and effective application to the intended purpose. This is his device, as
built by him for mines, and as described by him to the Royal Society, then
already (1698) formed and in operation, and to the public through his little
book, " The Miner's Friend; or, A Description of an Engine to raise
Water by Fire described, and the Manner of fixing it in Mines, with an Account
of the several Uses it is applicable to, and an Answer to the Objections
against it. Printed in London in 1702 for S. Crouch." It was distributed
among the proprietors and managers of mines, who were then finding the flow
of water at depths so great as, in some cases, to bar further progress.
The engraving of the engine was reproduced, with the description, in
Harris's " Lexicon Technicum," 1704; in Switzer's "Hydrostatics,"
1729; and in Desagulier's " Experimental Philosophy," 1744.
In Figure 2, LL is the boiler in which steam is raised, and through the
pipes it is alternately let into the vessels PP. Suppose it to pass into
the left-hand vessel first. The valve M being closed, and r being opened,
the water contained in P is driven out and up the pipe S to the desired
height, where it is discharged. The valve r is then closed, and the valve
in the pipe O; the valve Mis next opened, and condensing water is turned
upon the exterior of P by the cock Y, leading water from the cistern X.
As the steam contained in P is condensed, forming a vacuum there, a fresh
charge of water is driven by atmospheric pressure up the pipe S. Meantime,
steam from the boiler has been let into the righthand vessel Pp, the cock
W having been first closed, and R opened. The charge of water is driven
out through the lower pipe and the cock i, and up the pipe S as before,
while the other vessel is refilling preparatory to acting in its turn. The
two vessels are thus alternately charged and discharged, as long as is necessary.
Savery's method of supplying his boiler with water was as follows:- The
small boiler, D, is filled with water from any convenient source, as from
the standpipe, S. A fire is then built under it, and when the pressure of
steam in D becomes greater than in the main boiler, a communication is opened
between their lower ends, and the water passes, under pressure, from the
smaller to the larger boiler, which is thus " fed " without interrupting
the work. G and IV are gaagecacks, by which the height of water in the boilers
is determined; they were first adopted by Savery.
Here we find, therefore, the first really practicable and commercially valuable
steamengine. Thomas Savery is entitled to the credit of having been the
first to introduce a machine in which the power of heat, acting through
the medium of steam, was rendered generally useful. It will be noticed that
Savery, like the Marquis of Worcester, used a boiler separate from the waterreservoir.
He added to the 'watercommanding engine of the marquis the system of szerfacecondensaticn,
by which he was enabled to charge his vessels when it became necessary to
refill them; and added, also, the secondary boiler, which enabled him to
supply the workingboiler with water without interrupting its action. The
machine was thus made capable of working uninterruptedly for a period of
time only limited by its own decay. Savery never fitted his boilers with
safetyvalves, although it was done later by others; and in deep mines he
was compelled to make use of higher pressures than his rudely constructed
boilers could safely bear."
In this case, we find an illustration of a very common fact in the history
of inventions: The originator of this machine was probably, perhaps undoubtedly,
the second Marquis of Worcester; but the practical constructor, and the
finally successful inventor, was Savery, the man who combined inventive
with constructive power and business ability in that way which is almost
always essential to complete success. Savery was more an "exploiter"
of this invention than its author. Yet he did introduce some excellent modificationsof
details, and the various practically useful minutiae which so often are
the prime requisite to commercially satisfactory work. A glance at the drawings
of the machine, however, and a comparison with the modern steamengine will
show that this was not only not a steamengine in the usual sense, a train
of mechanism, but that it belongs to an entirely different class of apparatus.
A real steamengine was only invented after experience with the Savery apparatus
had shown it to be a wasteful, dangerous, and comparatively rude contrivance
for the application of steam to the work of raising water. It was wasteful
in consequence of the fact that it applied the pressure of the steam at
the surface of the cold water to be raised, and was thus certain to condense
much more than it could usefully employ; it was dangerous in consequence
of the fact that it must necessarily use pressures exceeding those of head
of water to be encountered, and higher than the mechanics of that time could
make their boilers and "forcing vessels" capable of safely withstanding.
More than one explosion actually occurred.
It is here that we meet with perhaps the greatest of all the inventors of
the steam engine,the man who for the first time produced a steamengine of
the modern type; a train of mechanism, in which a steam engine was constructed
and applied to another machine for the purpose of acting as its "prime
mover," an engine operating a pump. This greatest of the whole line
of inventors, considered from the point of view of the historian of the
engine and the student of its philosophy, was, not Watt, but Newcomen, or
perhaps more precisely, two mechanics, Thomas Newcomen and John Calley or
Cawley, who patented the new engine, 1705, soon after Savery's machine had
come to be fairly well known. Savery also controlled some of the patents
incorporated in the new arrangement, and took an interest with its inventors,
and shared their profits.
Newcomen's engine, by employing steam of low, hardly more than atmospheric,
pressure, evaded the dangers inherent in that of Savery, and by applying
the steam to move a piston in a cylinder apart from the pump, secured comparatively
economical performance. It promptly displaced the older and ruder contrivance,
and came into use all over Europe, as constructed later by Smeaton and other
great engineers of the day. As finally given form by these able men, it
is seen in the next engraving, which shows the machine as built by Smeaton
in 1774, for the Long Benton colliery.' The boiler is not shown in the sketch.
Figure 3 illustrates its characteristic features.
The steam is led to the engine through the pipe, C, and is regulated
by turning the cock in the receiver, which connects with the steamcylinder
by the pipe, X, which latter pipe rises a little way above the bottom of
the cylinder, GZ, in order that it may not drain off the injection water
into the steampipe and receiver.
The steam cylinder, about 10 ft. (3 m.) in length, is fitted with a carefullymade
piston, G, having a flanch rising 4 or 5 inches (.1 to 1.25 m.) and extending
completely around its circumference, and nearly in contact with the interior
surface of the cylinder. Between this flanch and the cylinder is driven
a "packing" of oakum, which is held in place by weights; this
prevents the leakage of air, water, or steam past the piston, as it rises
and falls in the cylinder at each stroke of the engine. The chain and pistonrod
connect the piston to the beam IS. The archheads at each end of the beam
keep the chains of the pistonrod and the pumprods perpendicular and in line.
A "jack-head" pump, 1W, is driven by a small beam deriving its
motion from the plugrod at g, raises the water required for condensing the
steam, and keeps the cistern, O, supplied. This "jackhead" cistern
is sufficiently elevated to give the water entering the cylinder the velocity
requisite to secure prompt condensation. A wastepipe carries away any surplus
water. The injectionwater is led from the cistern by the pipe, PP, which
is two or three inches in diameter; and the flow of water is regulated by
the injectioncock, r. The cap at the end, d, is pierced with several holes,
and the stream thus divided rises in jets when admitted, and, striking the
lower side of the piston, the spray thus produced very rapidly condenses
the steam, and produces a vacuum beneath the piston. The valve, e, on the
upper end of the injectionpipe, is a checkvalve to prevent leakage into
the engine when the latter is not in operation. The little pipe, f, supplies
water to the upper side of the piston, and, keeping it flooded, prevents
the entrance of air when the packing is not perfectly tight.
The "workingplug," or plugrod, e, is a piece of timber slit vertically,
and carrying pins which engage the handles of the valves, opening and closing
them at the proper times. The steamcock, or regulator, has a handle, h,
by which it is moved. The iron rod, i i, or spanner, gives motion to the
handle, h. The vibrating lever, k , called the Yor the " tumbling bob,"
moves on the pins, m n, and is worked by the levers, e p, which in turn
are moved by the plug tree. When a is depressed, the loaded end, k, is given
the position seen in the sketch, and the leg, /of the Y strikes the spanner,
i i, and, opening the steamvalve, the piston at once rises as steam enters
the cylinder, until another pin on the plugrod raises the piece, P, and
closes the regulator again. The lever, q r, connects with the injectioncock,
and is moved, when, as the piston rises, the end, y, is struck by a pin
on the plugrod, and the cock is opened and a vacuum produced. The cock is
closed on the descent of the plugtree with the piston. An educationpipe,
R, fitted with a clock, conveys away the water in the cylinder at the end
of each downstroke; the water thus removed is collected in the hotwell,
S, and is used as feedwater for the boiler, to which it is conveyed by the
pipe T. At each downstroke, while the water passes out through X, the air
which may have collected in the cylinder is driven out through the "
sniftingvalve," s. The steamcyllander is supported on strong beams,
t t; it has around its upper edge a guard, v, of lead, which prevents the
overflow of the water on the top of the piston. The excess of this water
flows away to the hotwell through the pipe W.
Catchpins, x, are provided, to prevent the beam descending too far should
the engine make too long a stroke; two wooden springs, yy, receive the blow.
The great beam is carried on sectors Z to diminish losses by friction.
Comparing this machine with that of Savery, it is seen that the dangers
of the form previously in use are here evaded, while economy is enormously
promoted by the change. As it is here practicable to employ steam of but
slightly more than atmospheric pressure, no danger of explosions consequent
upon high pressure in regular working is encountered. By the separation
of the pump from the working cylinder, and the application of the steam
to a piston, instead of to a surface of cold water, the immense condensation
to which it was subjected in the Savery engine is largely reduced. Thus
both safety and economy are gained. It is therefore not at all surprising
that this new invention should have come immediately into general use, and
should have promptly become the standard form of the steam engine for its
time. It was built not only for all the principal mines of Great Britain,
but alsofor those of the continent of Europe; and long after the death of
its inventors the genius of that greatest of engineers of his time, Smeaton,
continued to sustain it and to keep it in use, even as a rival of the most
famous of this whole life of inventions,-that of James Watt, who now comes
upon the scene. Smeaton himself built a large number of these engines; and
at the time of his death, about the end of the eighteenth century, there
were not less than a hundred Newcomen engines in Great Britain, and many
elsewhere in Europe.
Notwithstanding the great advantage possessed by this engine when compared
with that of Savery, it was, compared with our modern standards, a very
wasteful machine. Its wastes occurred through the same causes precisely
as those operating in the case of its predecessor, and though in less degree,
still to a very serious extent. In the operation of the pumpend it had become
efficient; but the steamcylinder was both a powerproducing mechanism and
a condenser of steam,- for the condensation of the one workingcharge was
produced by the introduction of water, cooling the cylinder itself, as well
as the steam which it contained. This cooling compelled a subsequent heating
by the next charge of steam, and consequent condensation and waste proportional
to the quantity thus demanded,-a very large fraction of all entering the
engine. Its "duty" was about six millions of pounds of water raised
one foot high by a bushel of coals,-the usual measure of efficiency of engines
in those days. This was but about a quarter of that obtained a little later
by Watt, and but a tenth of that secured ultimately by his best engines.
It was about five per cent of what is today considered the maximum duty
of the modern engine of the best type. It is to James Watt that we owe the
latest and crowning improvements of the steamengine, as we know it today.
A half century after Newcomen he found among the collections of the then
and still celebrated University of Glasgow always famous for its success
in the promotion of the physical sciences-a model of the stillused engine
of that earlier and no less deserving inventor. He was, in the course of
his duty as the instrumentmaker to the college, called upon to put this
little machine in repair; and having done so, he became interested in studying
its working. He was surprised to find that its steam cylinder absorbed,
each stroke, four times as much steam as its measurement would indicate
to be possible, three fourths of that entering being evidently condensed,
and only one fourth doing work. This waste of seventyfive per cent of all
the steam supplied, and of a similar proportion of the fuel used in generating
it, and of the money demanded for the operation of the engine, seemed so
extraordinary that the active mind of the great inventor was at once applied
to remedy so singular and immense a loss.
Watt saw at once that the remedy must consist in some way of reducing this
liquefaction of the steam by, as he said, "keeping the steamcylinder
as hot as the steam entering it." This he did by first effecting the
condensation of the steam in a separate condenser, instead of in the cylinder;
then surrounding the cylinder itself by a " steamjacket," in which
he kept steam at boilerpressure, thus preventing any cooling off of the
engine during the period of its operation. In his patent of 1769, he says,-
My method of lessening the consumption of steam, and consequently fuel,
in fireengines, consists in the following principles:-
The earliest engines of the kind, and of any considerable size, were
those set up in the Albion Mills, near Blackfriars' Bridge, London, in 1786,
and destroyed when the mills burned in 1791. These were a pair of engines,
of fifty horsepower each, and geared to drive twenty pairs of stones, making
fine flour and meal. Previous to the erection of this mill the power in
all such establishments had always been derived from windmills and waterwheels.
At the time of Watt's death, 1819, the steamengine had thus been brought
into its now familiar and standard form, and had been prepared, by its various
modifications of detail, to do its work in all now usual directions. The
engine itself was substantially complete in form. It had been given such
construction as would permit the expansive use of the motorfluid, and thus
the attainment of high economy; the wastes had been reduced to a comparatively
small amount; and the applications of the machine to the raising of water,
the driving of mills, the impulsion of railway carriages, and of vessels,
had been proposed and, tentatively, begun in all directions. It was now
possible to begin a new line of engineering development,- that of application
to all the purposes of modern life. It is this which has been the distinctive
industrial characteristic of the nineteenth century. As we have seen, Watt
may not claim the honour of being the inventor of the steamengine; but he
is unquestionably entitled to that of having been the most fruitful of inventors,
and the man to whom most credit is due for having applied the machine to
its myriad purposes, making it the universal servant and friend of mankind.
It is this which entitles him to the famous eulogy in his epitaph, as the
inventor who, " directing the force of an original genius, early exercised
in philosophic research, to the improvement of the steam engine, enlarged
the resources of his country, increased the power of man, and rose to an
illustrious place among the most eminent followers of science, and the real
benefactors of the world."