consisted of a hollow sphere into which the steam was admitted;
projecting from the sphere were two arms, from which the steam escaped
by three holes on the side of _each_ arm opposite to that of the
direction of its revolution, which, by removing the power from off the
one part of _each_ arm, caused it to revolve in the direction opposite
to that of the hole that allowed the steam to escape. This kind of
engine has been for some years in use by Mr. Ruthven of Edinburgh. There
are others who have followed very closely on Hero's plan in more ways
than one; for instance, it is the common Barker's mill, though with this
difference, that his mill is driven by water instead of steam: Avery,
also, made a steam-engine almost exactly the same. I may here, perhaps,
just be allowed to mention what a little water and coal will produce, as
it will show at once from whence our power is derived. "A pint of water
may be evaporated by two ounces of coal; in its evaporation it swells to
216 gallons of steam, with a mechanical force equal to raising a weight
of thirty-seven tons one foot high." A pound of coal in a locomotive
will evaporate about five pints of water, and in their evaporation these
will exert a force equal to drawing two tons on a railway a distance of
one mile in two minutes. A train of eighty tons weight will take 240
passengers and luggage from Liverpool to Birmingham and back, each
journey about four and a quarter hours; this double journey of 190 miles
being effected by the combustion of one and a half tons of coke, worth
about twenty-four shillings. To perform the same work by common road
would require twenty coaches, and an establishment of 3800 horses, with
which the journey would be performed each way in about twelve hours,
stoppages included. So much for the advantages of steam.
The Romans are supposed to have had some knowledge of the power of
steam. Among amusing anecdotes, showing the knowledge the ancients had
of steam, it is told that Anthemius, the architect of Saint Sophia,
lived next door to Zeno. There existed a feud between them, and to annoy
his neighbour, Anthemius had some boilers placed in his house containing
water, with a flexible tube which he could pass through a hole in the
wall under the floor of Zeno's dwelling; he then lit a fire, which soon
caused steam to pass through the tube in such a quantity as to make the
floors to heave as if by an earthquake. But to return. We next come to
Blasco de Garay (A.D. 1543), who proposed to propel a ship by the power
of steam. So much cold water seems to have been thrown on his engine,
that it must have condensed all his steam, as little notice is taken of
it except that he got no encouragement. We find that it has also been
used by some of the ancients in connection with their deities.
Rusterich, one of the Teutonic gods, which was found in an excavation,
proves how the priests deceived the people. The head of this one was
made of metal and contained a pot of water. The mouth and another hole
in the forehead being stopped by wooden plugs, a fire of charcoal was
lighted under this pot of water, and at length the steam drove out the
plugs with a great noise, and the god was shrouded in a mist of steam
which concealed him from his astonished worshippers.
In 1629, Giovanni Branca of Loretto in Italy, an engineer and architect,
proposed to work mills and other machinery by steam blowing against
vanes, much in the same way as water does in turning a wheel. The waste
of steam in such a plan is so obvious, that it is not to be wondered at
that it did not produce any great results, as we all know that the
moment we let steam out of his case, the case is all up with him, and he
dies a natural death. He is a most delicate yet powerful agent, and
requires to be kept warm in all weathers--this fact does not seem to
have struck Mons. Branca when he let him out of his boiler.
The next person we come to, and perhaps the first of any note, is the
Marquis of Worcester in 1663 (died 1667). He was a man who seems, as far
as history tells us, to have taken a great interest in furthering the
advancement of steam. He was not contented with one invention, but
published a book entitled "A Century of Inventions," and in this work he
describes a means of raising water by the pressure of steam. The Marquis
appears to have been a politician as well as an inventor, as we find he
was engaged on the side of the Royalists in the Civil Wars of the
Revolution, lost his fortune and went to Ireland, where he was
imprisoned. Escaping to France, from thence he returned to London as a
secret agent of Charles II., but was detected and imprisoned in the
Tower, where he remained till the Restoration, when he was set at
liberty. One day, while in prison, he observed the lid of the pot in
which his dinner was being prepared lifted up by the vapour of the water
boiling inside. Reflecting on this, he turned his mind to the matter,
and thought that this vapour, if rightly applied, might be made a useful
moving power. He thus describes his invention in his 68th Article: "I
have contrived an admirable way to drive up water by fire, not by
drawing or sucking it upwards, thirty-two feet. But this way hath no
bounds, if the vessels be strong enough." He then goes on to say, that
"having a way to make his vessels, so that they are strengthened by the
force within, I have seen the water run like a constant stream forty
feet high. One vessel rarified by fire driveth forty of cold water, and
one being consumed, another begins to force, and refill with cold water,
and so on successively, the fire being kept constant. The engineman
having only to turn two cocks, so as to connect the steam with the one
or the other vessel."
In this engine, if it can be called an engine, we see that the Marquis
had a good idea of the power of steam, but he had none, you will
observe, as to the action of the condensation which would immediately
take place when the steam from the boiler was brought into contact with
the cold water to be raised. Therefore this plan would be most
expensive, on account of the great loss of steam by condensation. It
was, however, quite able to produce the effect, though only equal to
raising 20 cubic feet of water, or 1250 lbs., one foot high by one pound
of coal, or about the two-hundredth part of the effect of a good
steam-engine. After this, of course, it proved of no avail; but still we
may say that the Marquis of Worcester was among the first who tried to
make, and did do so, steam a moving power.
Our next is Denys Papin (died 1710), a native of Blois, in France, who
was mathematical professor at Marpurg. To him is due the discovery of
one of the qualities of steam--its condensation, so as to produce a
vacuum, to the proper management of which our modern engines owe much of
their efficacy. Papin seems to have been the first who conserved the
idea of the cylinder and piston, which he made to act on atmospheric
principles--that is to say, he took a cylinder with a piston moving up
and down in it, and found that by removing the air from under the piston
in the cylinder, that the pressure of the atmosphere would drive it down
to the bottom of the cylinder: this he performed by admitting steam, and
then condensing it rapidly, so causing the required vacuum. The pressure
of the atmosphere is as near as may be 16 lbs. on every square inch of
surface on the globe: this is obviously the weight of the columns of
air extending from that square inch of surface upwards to the top of the
atmosphere. This force is thus measured: Take a glass tube 32 inches
long, open at one end and closed at the other; provide also a basin full
of mercury; let the tube be filled with mercury and inverted into the
basin. The mercury will then fall in the tube, till it gets to that
height which the atmosphere will sustain. This is nothing more than the
barometer used in all our houses. If the action of the tube be equal to
a square inch, the weight of the column of mercury in the tube would be
exactly equal to the weight of the atmosphere on each square inch of
surface. Thus Papin discovered a great step in the steam-engine, though
it was not much acted on for some years; he was also the first who
proposed to drive ships with paddles worked by steam.
We now come to Thomas Savory, who got a patent in 1698 for a method of
condensing steam to form a vacuum. Savory describes his discovery in
this way:--Having drank a flask of wine at a tavern, he flung the empty
flask on the fire, and then called for a basin of water to wash his
hands. A little wine remained in the flask, which of course soon
boiled, and it occurred to him to try what effect would be produced by
putting the mouth of the flask into the cold water. He did this, and in
a moment the cold water rushed up and filled the flask, this being
caused by the steam being condensed and leaving a vacuum, which Nature
abhors, and rather than permit this the water rushed up and took the
place formerly occupied by the now condensed steam. We see by this in
how simple a way great ends are produced, and in the age in which this
happened, the result may be indeed be said to have produced a great end.
The engine of Savory was used for some years as a machine to raise
water. The principle of his engine was just as I have stated, and
consisted of two cases and other various parts, and this engine
possessed advantages over that of the Marquis of Worcester in sucking up
the water as well as forcing.
Savory's engine consisted of two steam vessels connected to a boiler by
tubes; a suction pipe, or that pipe which leads from a pump of the
present day to the well, and communicating with each of the steam
vessels by valves opening upwards; a pipe going from these steam vessels
to any required height to which the water is to be raised. The steam
vessels were connected to this pipe by other valves, also opening
upwards, and by pipes. Over the steam vessels was placed a cistern,
which was kept filled with _cold_ water. From this proceeded a pipe with
a stopcock. This cistern was termed the condensing cistern, and the pipe
could be brought over each steam vessel alternately from the boiler.
Now, suppose the tubes to be filled with common air, and the regulator
placed so that one tube and the boiler are made to communicate, and the
other tube and the boiler closed, steam will fill one of the steam
vessels through one tube; at first it will condense quickly, but erelong
the heat of the steam will impart its heat to the metal of the vessel,
and it will cease to condense. Mixed with the heated air, it will
acquire a greater force than the air outside the valve, which it will
force open, and drive out the mixture of air and steam, till all the air
will have passed from the vessel, and nothing but the vapour of water
remain. This done, a cock is opened, and the water from the cistern is
allowed to flow over the outside of the steam vessel, first having
stopped the further supply of steam from it; this produced the
immediate condensation of the steam contained in it, by the temperature
being brought down again by the cold water, and the condensation thus
produced caused a vacuum inside the vessel. The valve will then be kept
closed by the atmosphere outside, and the pressure of the air on the
surface of the water in the well or reservoir will open another valve,
force the water up the pipe, till, after one or two exhaustions--if I
may so term it--it will at last reach the second vessel. Thus far the
atmosphere has done all the work, but at last the water fills the
vessel, and then comes the forcing point. Now the power of the steam
itself is used to drive the water up the pipe. The steam is again let
into the vessel, now filled in whole, or at least in great part, with
water; at first it will, as before, condense rapidly, but soon the
surface of the water will get heated, and as hot water is lighter than
cold, it will keep on the surface, and the pressure of the steam from
the boiler will drive all the water from the vessel up the pipe. When it
is empty the cock is again opened, and the steam, which the vessel by
this time only contains, is again condensed, and the same process which
I have just described is again commenced and carried out, thus making
Savory's engine a complete pump by the aid of the vapour of water as
raised by fire.
Savory had the honour of showing this engine to His Majesty William III.
at Hampton Court Palace, and to the Royal Society. He proposed the
following uses, which perhaps may as well be mentioned, as they show how
little was then known of the real value of the power of steam:--1. To
raise water to drive mill-wheels--fancy erecting a steam engine now, of
say fifty horse-power, to raise water to turn a wheel of say thirty; 2.
To supply palaces and houses with water; 3. Towns with water; 4.
Draining marshes; 5. Ships; 6. Draining mines. There is one more thing I
may mention as curious, that though the steam he used must have been of
a high pressure, he did not use a safety-valve, though it had been
invented about the year 1681 by Papin. The consumption of fuel was
enormous in Savory's engine, as may easily be perceived from the great
loss of steam by condensation. Nevertheless, it was on the whole a good
and a workable engine, as we find the following said of it by Mr.
Farey:--"When comparison is made between Captain Savory's engine and
those of his predecessors, the result will be favourable to him as an
inventor and practical engineer. All the details of his invention are
made out in a masterly style, so as to make it a real workable engine.
His predecessors, the Marquis of Worcester, Sir S. Morland, Papin, and
others, only produced outlines which required to be filled up to make
them workable."
I must not detain you much longer before I proceed to the great Watt,
but I will just name Newcomen, who invented an engine with a cylinder,
and introduced a beam, to the other end of which he fixed a pump rod
like a common or garden pump. He made the weight of the pump and beam to
lift the piston, and then let the steam enter below the piston and
condensed it by a jet of water, thus causing a vacuum, when the pressure
of the atmosphere drove the piston from the top to the bottom of the
cylinder and lifted the pump rods in the usual way. There were various
cocks to be opened and shut in the working of this engine for the right
admission of steam and water at the required moments, a task which was
performed by boys who were termed cock-boys. I will now mention an
instance which, though in practice not to be imitated, yet was one of
those happy accidents which sometimes turn out for the best. One of
these boys, like many, more fond of play than work, got tired of turning
these cocks day by day, and conceived the idea of making the engine do
it for itself. This idle boy--we will not call him good-for-nothing, as
he proved good for a great deal in one way--was named Humphrey Potter,
and one day he fixed strings to the beam, which opened and shut the
valves, and so allowed him to play, little thinking this was one of the
greatest boons he could possibly have bestowed on the world at large,
for by so doing he rendered the steam-engine a self-acting machine.
We now come to a period which was destined to advance the cause of steam
to a far greater extent--in fact, the time which rendered the
steam-engine the useful and valuable machine it now is. This is the time
of James Watt. This great man, be it said to the credit of Scotland, was
born in Greenock, on the Clyde, on the 19th January 1736. His
grandfather was a farmer in Aberdeenshire, and was killed in one of the
battles of Montrose. His father was a teacher of mathematics, and was
latterly chief magistrate of Greenock. James Watt, the celebrated man of
whom I now speak, was a very delicate boy, so much so, that he had to
leave school on account of his health, and was allowed to amuse himself
as he liked. This he did in a scientific way, however, as an aunt of his
said to him one day: "Do you know what you have been doing? You have
taken off and put on the lid of the teapot repeatedly; you have been
holding spoons and saucers over the steam, and trying to catch the drops
of water formed on them by it. Is it not a shame so to waste your time?"
Mrs. Muirhead, his aunt, was little aware that this was the first
experiment in the way which afterwards immortalised her nephew.
In 1775 Watt was sent to London to a mathematical instrument maker, but
could not stay on account of his health, and soon afterwards came back
to Glasgow. He then got rooms in the College, and was made mathematical
instrument maker to the University, and he afterwards opened a shop in
the town. He was but twenty-one years of age when he was appointed to
this post in the College, and his shop became the lounge of the clever
and the scientific. The first time that his attention was directed to
the agency of steam as a power was in 1734, when a friend of his, Mr.
Robinson, who had some idea of steam carriages, consulted him on the
subject,--little is said of this, however. In 1762 Watt tried some
experiments on high-pressure steam, and made a model to show how motion
could be obtained from that power; but did not pursue his experiments on
account of the supposed danger of such pressure. He next had a model of
Newcomen's engine, which would not work well, sent him to repair. Watt
soon found out its faults, and made it work as it should do. This did
not satisfy him, and setting his active mind to work, he found in the
model that the steam which raised the piston had of course to be got rid
of. This, as a natural consequence, caused great loss of heat, as the
cylinder had to be cooled so as to condense the steam; and this led him
at last, after various plans, to adopt a separate vessel to condense
this steam. Of course, if you wish to save fuel, it is necessary that
the steam should enter a heated cylinder or other vessel, or else all
the steam is lost,--or in other words, condensed,--that enters it, until
it has from its own heat imparted so much to the cylinder as to raise
it to its own temperature, when it will no longer condense, and not till
then does it begin to exert its elastic power to produce motion. This
was the great object gained by James Watt, when, after various
experiments, he gave up the idea altogether of condensing steam in its
own or working cylinder, and then made use of a separate vessel, now
called the condenser.
The weight of steam is about 1800 times less than water. I may here
perhaps mention also that water will boil at 100 degrees Fahr. in vacuo,
whereas in atmosphere it takes 212 degrees to boil. There is also a
thing perhaps worth knowing to all who wish to get the most stock out of
bones, &c., that if they are boiled in a closed vessel, that is to say,
under a pressure of steam, a very large increase in quantity of the
stock will be produced, because the heat is increased. A cubic inch of
water, evaporated under _ordinary_ atmospheric pressure, will be
converted into a cubic foot of steam; and a cubic inch of water,
evaporated as above, gives a mechanical force equal to raising about a
ton a foot high.
The next great improvement of Watt, in addition to the condenser, is the
air-pump, the use and absolute necessity for which you will understand
when I explain its action. Watt first used it for his atmospheric
engine. The piston of this engine was kept tight by a flow of oil and
water on the top, which tended to make the whole a troublesome and
bad-working machine. The cold atmosphere, as the piston went down, of
course followed it and cooled the cylinder. On the piston again rising,
some steam would of course be condensed and cause waste. If the
engine-room could be kept at the heat of boiling water, this would not
have been the case, but the engineman who could live in this heat would
also require to be invented, and so this had to be given up. Watt's next
and most important step was the one which brings us to talk of the
steam-engine as it now is in the present day. This important step was
the idea, of making the steam draw down the piston, as well as help to
drive it up; in the first engines it was raised by the beam, and steam
used only to cause a vacuum, so as to let the air drive it down. All
before this had been merely steps in advance, like those of children,
who must walk before they can run; so was it with the steam-engine. It
was uphill work for many years, and the top of the hill cannot be said
to have been readied till Watt worked out this grand idea. The first
engine could only be called atmospheric; now it was destined to become
in reality a steam-engine. Time would fail were I to attempt to go into
any details of all the experiments through which Watt toiled to bring
his ideas to perfection--enough to say that he did so; and I trust you
will be able, through the description I will endeavour to give, to
understand how well his labour was bestowed, and how beautiful the
result has proved for the benefit of the world at large. In 1773, Watt
removed to Soho, near Birmingham, where a part of the works was allotted
to him to erect the machinery necessary to carry out his inventions on a
grand scale.
We must now proceed to some of the useful points of the engine, all I
have before mentioned simply relating to the inventors and improvers;
but having brought it so far, I may now, I think, proceed further. The
first use of the steam-engine was simply to raise water from mines, and
for long it was thought it could be used for nothing else; so much so,
that it was at one time used to raise water to turn wheels and thus
produce motion. One of its first uses after it became a really useful
machine was to propel ships, though many a weary hour was spent to bring
it to this point. There is a very pretty monument on the Clyde,
dedicated to Mr. Bell, who I believe was the first person who
successfully brought steamers to work on its waters. The first who used
steam for ships was Mr. James Taylor, in conjunction with Mr. Miller of
Dalswinton. The danger of the fire-ship took such hold on people's minds
that it was with great toil and difficulty they were persuaded to
venture on the face of the waters in such dangerous and unseamanlike
craft. But go to Glasgow Bridge any day, and you will see how time has
overcome fear and prejudice, for our ocean is covered with steamers of
all sizes. It is not many years ago since it was said that steamers
could never reach America; this has given way to proof, and even
Australia has been reached by steam. I know of a steamer building which
could carry the whole population of this place and not be full; she is
680 feet or 226 yards long, and a large vessel would hang like a boat
alongside her.
The first attempt at giving motion by steam to ships was of course only
in one way--by a ratchet at the end of a beam, at one moment driving
and the next standing still. This was on account of the engine being
only in power one half of the stroke; but by the double-acting engine
being introduced, and the steam acting both ways, it became at last a
steady mover (without the aid of two or three cylinders, as in the first
engines, one to take up the other as the power was given off), by a
ratchet on the end of a beam or else a chain. This acted on the shaft
which moved the paddles. It is to Watt that we are indebted for the
crank and direct action, so as to give a circular motion to the wheels.
We find in 1752 a Mr. Champion of Bristol applied the atmospheric engine
to raise water to drive a number of wheels for working machinery in a
brasswork, in other words, a foundry. Also, in Colebrokedale,
steam-engines were used to raise water that had passed over the wheel,
so as to save water. All these plans have, however, now passed by, like
the water over the wheel, and we now have the engine the prime
mover--the double action of the steam on the piston, this acting on the
sway beam, and the beam on the crank, which, by the assistance of the
fly-wheel on land or fixed engines, gives a uniform motion to the
machine. All these have now enabled us to apply the engine as our grand
moving power. One great and important point in the engine is the
governor, and the first modes of changing the steam from the top to the
bottom of the cylinder were cumbrous, till the excentric wheel was
devised.
Boilers also have to be attended to--these were at first rude and now
would be useless. They were unprovided with valves, gauge-cocks, or any
other safety, all of which are now so well understood that nothing but
carelessness can cause a blow-up. One of the greatest causes of danger
is that of letting there be too little water in the boiler, and thus
allowing it to get red-hot, when, if you let in water, such a volume of
steam is generated that no valve will let it escape fast enough. Force
or feed pumps are also required to keep the water in the boiler at a
proper height, which is ascertained by the gauge-cocks. Mercury gauges
for low pressure act according to the pressure of the atmosphere;
high-pressure boilers of course require a different construction, as the
steam is greater in pressure than the air.