Francis Lieber.

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tills law, steam which occupied 1 cubic ft. at 20 Ibs. absolute pressure, would occupy 4
cubic ft. at 5 Ibs., and half a cubic ft. at 40 Ibs. absolute pressure.

Steam, however, as commonly used in the steam-engine, is not superheated, but ured
7indi-r the conditions given in the table. It is then called saturated steam, and differs
sensibly from the condition of a perfect gas. If the pressure (p) be given in pounds per
bq. in., and the product (pv) of pressure and volume in foot-pounds, then the formula,

log. (pr) = 4.675 + .061 log. p*

gives results accurate enough at all ordinary pressures, and can be very easily applied.
The volume, instead of increasing inversely as the pressure, increases less rapidly; the
difference, though not very great, is large enough to be taken into account in all calcu-
lations as to the efficiency ami behavior of steam in a steam-engine.

Another fact regarding the constitution of steam requires attention; from ils impor-
tance in point of economy. It would naturally be expected that it would take much
more heat or fuel to convert a pound of water into steam at a higher than at a lower tem-
perature and pressure. In reality, however, the difference is very slight. Referring
back to the table, it will be seen that it requires 1146.6 units of heat to raise a pound of
water from 32 to 212, and evaporate it at that temperature; of these, 180 are expended
in raising the temperature, while 1146.6 180, or 966.6 units, become latent in the
steam, it only requires 1171.2 units, however (261 sensible, and 910.2 latent), to raise
the water to 293, and evaporate it at that temperature; for the latent heat falls nearly ns
fast as the sensible heat rises. The additional heat required is thus only a little over 2
per cent, while the pressure which is, cceteris paribus, a measure of the work the steam
will do is more than quadrupled. In this way, a large increase of power in any engine
may be obtained by a small additional expenditure of fuel, and consequently sieam of 3,
high pressure is now being used for all purposes, its economy and advantages being fully
recognizedjby engineers. It was thought for a long time that the Mai heat of strum
that is, the sum of the sensible and latent heats was constant at all tempt rat u res-; but
this is not strictly the case, although the table shows that the difference, for ordinary
ranges of pressure, is but trifling. See HEAT and STEAM-ENGINE.

STEAM-CAREIAGE. Very early in the history of steam-locomotion, projects were
formed for running steam-carriages on common roads not to draw a train of vehi-
cles after them, but each carnage to have passenger-accommodation as well as steam-
power. Robison suggested such a thing to Watt so far back as 1759. A French inven-
tor, Cugnot, tried a steam-carriage at Paris in 1770, which went with so much force*
ns to dash down a brick wall, and thereby 'deter other inventors. In 1782, Murdoch
exhibited a model of a steam carriage; in 1784, Watt described his plans for another;
and in 1786 Symington produced" a model of a third. In the last-named year,
too. Oliver Evans announced certain projects of the kind in the United States. In
1802, Messrs. Trevethick and Vivian patented a-steam-carriage, planned on a much bet-
ter principle than any that had preceded it; they adopted high-pressure steam, of which
previous inventors had been afraid. The carriage was tried, but the ingenious patentees
received very little encouragement, and soon turned their attention to railway matters.
A long interval then passed without any new inventions in this kind of road-locomotion.
'"When Telford and other engineers had improved the roads and highways, inventors
were again induced to apply steam-power as a substitute for house-power to road- vehicles.
Bramah made a steam-carriage in 1821. on a plan patented by Julius Griffiths. Gordon
invented one in 1822, which worked something like a squirrel in a c;;ge, the engine
being within a cylinder which rolled along the ground; and another in 1824, which
appeared to walk upon six iron legs. Goldsworthy, Gurney, Burstall, Hill, James,
Hancock, Summers, Ogle, Heaton. Church, Dance, Field, Squire, Maceroni, Scott Rus-
sell, Hills, Sir James Anderson all invented new forms of steam-carriage between 1S24
and 1841. Some of these displayed great ingenuity, and attained a speed of 10 or 12
miles an hour on common turnpike roads. Sir Charles Dance ran such a carriage between
Gloucester and Cheltenham in 1831, doing the 9 miles in 55 minutes; but the oppo
sition of local interests put him down, after he had made 400 such trips without an acci-
dent, and carried a very large number of passengers. In the same year Mr. Hancock
began running his stfmn-carriage, called The Infant, regular! y between London and
Stratford; and some time afterward, Mr. Scott Russell ran fa's invention between Glas-
gow and Paisley. All these tlrrce were passenger-vehicles which plied for traffic on the
road. In the very numerous inventions from time to time brought forward, the passen-
gers were in some cases seated in front of the engine and boiler; in others, they were
seated behind; in others, the tank for water was placed beneath the passengers' feet;
while in a fourth kind there was a passenger-carriage, distinct from, but linked to, the

* Cotterill, Notes on the Theory of the Steam-engine, page 9.

791

Steam.

steam-locomotive. Xone of the inventions, however, attained to commercial success, so
many were the difficulties which beset them.

The. las! quarter of a century has exhibited inventions rather for heavy traction than
for passenger steam-carriages. One of the most remarkable of the latter kind is that
which the earl of Caithness drove, in 1864, from Inverness to his scat near Thurso. It
carried three or four p/rsons, and ascended and descended very steep inclines without
much variation of speed. As a question of profit or commercial advantage the inventors
of such engines now look to their employment on common roads, for dragging heavy
loads. Numerous patents-have been taken out, with this view, by Boydell, Bray, ('lay-
ton, Burrell. Fowler, Aveling, H. W. Thomson, and others. In Mr. Thomson's engines, >
or "road-steamers," the wheels are encircled by a complete ring, or tire, of india-rubber,
protected on the outside by a flexible sheath of steel plates. As engines for drawing
very heavy weights these have proved the most powerful yet invented, and several of
them by 1874 were constantly at work in Glasgow, dragging enormously heavy castings
and boilers from the workshops of the engineers to the railways or wharves. In ordi-
nary work, however, the ro:id steamers can hardly be said to have been a success. The
expense connected with the renewal of the india-rubber tires, and the other parts worn by
the constant jolting on common roads, has told very much against their adoption. Of
traction engines with iron wheels. Fowler's aud Aveling's are those most used. They
are very simple in construction, and cheap in comparison to Thomson's, although not
capable of doing the exceptionally heavy work we have just mentioned. Great
endeavors are now being made to design an "engine suitable for use upon .tramway lines
laid down on common roads, but as yet without complete success. Several acts of par-
liament have been passed to regulate the use of locomotives upon common roads.
Their regulations at tirst were severely restrictive, framed apparently rather to dis-
courage than to encourage enterprise. Now, however, that the engines are improved,
and their use more understood by the public, the popular feeling against the engines,
uiii '!i caused this legislation, is rapidly disappearing.

It h is !>; 'ii a favorite idea for many years with amateur and professional mechani-
cians I'e.sp.-cially th-. 1 former) to make a light carriage which could be used upon ordi-
nary nads, and which should contain a steam-engine and boiler to propel itself. In
spite of itmumerab!" a 1 tempts no permanent success has yet been obtained in this
direction, notwithstanding that great progress has been made in constructing steam
tracti -m engines for common roads. The fact seems to be th it, while a s'jlf-pro- (
polling steam-carriage to carry only the weight of a passenger or two can be made;
without much difficulty, its cost will bj proportionately so heavy, and the tro'ible of
keeping it in order as well as of working it, so great, that it will uot succeed commer-
cially.

The true application of steam upon common roads is in the drawing of heavy Im-l-i
which would otherwise require an inconveniently large number of hors; -s. Engines for
tiiis purpjs:- are called t/;t<-f/',,.',-e;}f//'/irx, and their use, notwithstanding determined, and
too often ignorant opposition, seems to be yearly on the increase. Traction-engines
may be divided into two classes those with rigid tires on their wheels, and those with
flexible tires. The former class is the older, and includes many ingenious but mistaken
contrivances for laving down what was equivalent to an endless railway for the engine
to run upon, which was at one time thought by many essential to it- The best

engines at present made with rigid tires are those of Messrs. Aveling and Porter of
Rochester, which are simple and substantial in construction, and ar;> u< - I largi iy both
in tills c tuntry and abroad. Of the second class of traction engines those fitted with
Thomson's patent india-rubber tires, and by the inventor called rn 1 -.sV/r-//' / - . arc tb.3
only ones that have come into anything like extended use. These tires are simply rings
of india-rube.r, 4 or ."> in. thick, stretched over the rim of the wheel, and protected by n
flexible circle of steel shoes from being damaged by stones, etc. The advantage of flexi-
ble tires is die greater adhesion (in proportion to weight) which they give to the engine,
and the saving the machinery from shocks and jars. They will doubtless be still more
largely used when more lengthened experience has perfected their construction, but the
great cost of the india-rubber has hitherto much hindered their extended adoption.

STEAM-CEANE. The application of steam to the working of cranes was an obvious
one, and is now universal where much hoisting work has to be done; it not only clients
a great saving in labor, but causes the work to be much more quickly don >. a consider-
ation quite as important. Steam-cranes and winches are now almost invariably used on
the ship along by means of a cable, and other purposes. When working on a wharf.
a id in many other situations, it is often very convenient that the crane should be niov-
ftbie, so that it may go to its work in the multitude of cases where that arrangement is
more convenient than the converge. For this purpose it is mounted on a plain railway
truck, either of wood or iron, the truck being generally provided with clamps at the
ends, by which it can be firmly secured to the rails when" lifting weiirhK The balance
construction, now universally adopted for portable cranes. wa invented or snu^^ted by
the late Mr. II. W. Thomson. O.K.. in 185(5 its essential feature being the use of the
boiler as a counterpoise to the weight to be lifted. The principal parts uf a su am-crane

&team.

792

are: 1. The boiler, which must be of some very simple construction, as it has so fre-
quently to be worked with excessively dirty water; 2. The framing, which is generally
made of cast-iron, and supports the boiler, the engine and gear, and the jib; 3. The
engine (which has almost always two small cylinders, and is fitted with reversing gear),
and the pinions, wheels, drums, etc., for the hoisting and other motions; 4. The "jib"
(either of wood or iron), over a pulley in the top of which the chain passes, and the pur-
pose of which is to enable the different objects to be lifted quite clear of the gi'ound,
and deposited, when necessary, on trucks, etc. ; 5. The pillar, which is firmly attached
to the truck, and which, passing upward through the center of the frame, forms the
'pivot on which it turns round ; 6. The truck itself, which supports the whole machine.
If the crane is stationary, the truck, of course, is not required, the bottom of the pillar
being imbedded in masonry; and for large cranes the boiler is generally made separate
from the machine itself, and sometimes the engines also. A portable balance steam-crane
is, when complete, fitted with the following motions: 1. Gear for hoisting, generally with
two or more speeds, to be used according to the weight to be lifted; 2. Gear for raining
or lowering the outer end of the jib; 8. Gear for slewing the jib (with boiler and frame
attached to it) ; 4. Gear for propelling the truck along the rails. A complete and well-
designed crane of this kind, made by Messrs. Alexander Chaplin & Co., of the Cranston-
hill works, Glasgow, will lift from 5 to 7 tons, according to the position of the jib.

STEAM-ENGINE. Steam-engines, in their infancy, were known as "fire" (that is,
Tieat) engines; and in point of fact thd older term is the more correct, because the water
or steam is only used as a convenient medium through which the form of energy which
we call heat is made to perform the required mechanical operations. In modern engines
sufficient heat is added to the steam to raise it to a very high pressure, and the excess of
this pressure over the pressure opposed to it (either atmospheric pressure or the still
lower pressure in a condenser) is both the cause and measure of the work clone by the
engine. In earlier machines, however, the steam was raised only to atmospheric press-
ure, and admitted into the engine only to be at once condensed by a jet of cold water.
The excess of the atmospheric pressure above the pressure in the partial vacuum caused
by the condensation was then the direct cause of work. Engines of this kind are not
now used ; they were called atmospJieric engines. As a source of power steam has many
advantages over wind and water. It is independent of the weather, may be applied any-
where, affords a constant equable motion, and is capable of indefinite increase. Its
invention, therefore, has caused a new era in the arts; and the revolution which it has
brought about in industry of all kinds, as.well as the influence it has had on civilization
in general, and must yet have in a higher degree, are altogether incalculable.

The invention of steam as a moving power is claimed by various nations; but the first
extensive employment of it, and most of tjpe improvements made upon. the steam-engine,
the world indisputably owes to the English and the Americans. It would appear that
as early as 1543 a Spanish captain, named Blasco de Garay, showed in the harbor .of
Barcelona a steamboat of his own invention. It is most likely that Blasco's engine was
on the principle of the JEolipile of Hero, invented 130 B.C., 'in which steam produces
rotatory motion by issuing from orifices, as water does in Barker's mill (q.v.X The
preacher Mathesius, in his sermon to miners (Nuremberg. 1562), prays for a man who
"raises water by fire and air," showing the early application of steam-power in Germany;
and the German engineer, Sol. de Cans, in the service of the elector palatine in Heidel-
berg, describes, in his work, Les Raisons des Forces Moumntes avec Diverges Machines
(Frankf. 1615), a steam-machine, which was merely a contrivance for forcing the water
contained in a copper ball through a tube by applying heat. An Italian engineer, G.
Branca, invented, in 1629, a sort of steam windmill; the steam being generated in a
boiler, was directed by a spout against the flat vanes of a wheel, which was thus set in
motion.

In England, among the first notices we have of the idea of employing steam as a pro-
pelling force, is that contained in a small volume.* published in 1647, entitled Tfie Art
of Gunnery, by Nat. Nye, mathematician; in which he proposes to "charge a piece of
ordnance without gunpowder," by putting water instead of powder, ramming down an
air-tight plug of wood, and then the shot, and applying a fire to the breech "till it burst
out suddenly." But the first successful effort was that of the marquis of Worcester. In
his Century of Inventions, the manuscript of which dates from 1655, he describes a steam-
apparatus by which he raised a column of water to the height of 40 feet. This, under
the name of "fire-waterwork," appears actually to have been at work at Vauxhall in
1656. Sir Samuel Morland in 1683 submitted to Louis XIV. a project 'for raising water
by means of steam, accompanying it with ingenious calculations and tables. The first
patent for the application of steam-power to various kinds of machines was taken out in
1698 by capt. Savery. In 1699 he exhibited before the Royal society a working model of
his invention. His engines were the first used to any extent in industrial operations;
they seem to have been employed for some years in the drainage of mines in Cornwall
and Devonshire. The essential improvement in them over the older ones was the use of
a boiler separate from the vessel in which the steam did its work. One vessel, in all

* The volume is in the possession of Mr. S. Holliday, to whom we are indebted for this fact.

793

Ktcam.

former engines, had served both purposes. He. made use of the condensation of steam
iia a close vessel to produce a vacuum, and thus raise the water to u certain height, after
which the elasticity of steam pressing upon its surface was made to raise it still further
in a second vessel.

In all the attempts at pumping-engines hitherto made, including Savory's, the steam
acted directly upon the water to be moved without any intervening part. To Dr.
Papin, a celebrated Frenchman, is due the idea of the piston. It was first used bv him
in a model constructed in 1690, where the cylinder was still made to do duty also as a
boiler; but in an improved steam-pump invented about 1700 he used it as a diaphrairm
floating on the top of the water in a separate vessel, or cylinder, and the steam, 'by
pressing on the top of it, forced the water out of the cylinder at the other end.

conjointly invented by Newt-omen, Cawley, and Savery. This machine held its own
for nearly seventy years, and was very largely applied to mines, so that it will be worth
while to give a somewhat more detailed description of it than of the others.

In this engine, which is shown in rig. 1, the previous inventions of 1

Newt-omen's engine
To one end of a beam

was ch icily used, like all former steam-engines, in raising water,
moving on an axis I, was attached the
rod, N, of the pump t> be worked; to
the other, the rod, M, of a piston P,
moving in a cylinder C, below. The
cylinder was placed over a boiler B, and
was connected with it by a pipe provided
with a stop-cock V, to cut off or admit
the steam. Suppose the pump-rod de-
pressed, and the piston raised to the top
of the cylinder which was effected by
weights suspended at the pump-end of
the beam the steam-cock was then
turned to cut off the steam, and a dash
of cold water was thrown into the cylin-
der by turning a cock R, on a water
pipe A, connected with a cistern C'.
This condensed the steam in the cylin-
der, and caused a vacuum below the pis-
ton, which was then forced dow y n by the
pressure of the atmosphere, bringing
with it the end of tlie beam to which it
was attached, and raising the other
along with the pump-rod. The cock
was then turned to admit fresh steam
below the piston, which was raised by
the counterpoise; and thus the motion
began anew. The opening and shutting
of the cocks was at tirst performed by an
attendant, but subsequently a boy named Humphrey Potter (to save, it is said, the
trouble of personal superintendence) devised a system of strings and levers by which
the engine was made to work its own valves. In 1717 Henry Heighten, an F.U.S. .
invented a simpler and more scientific system of "hand-gear," which rendered the
engine completely self-acting. During the latter part of the time that elapsed before
Watt's discoveries changed everything, Stneaton brought Ncwcomen's engine to a very
high degree of perfection. As the result of study and experiment he made many-
improvements in it, in the form of the boiler, the proportions of the cylinder, etc. It
was he, too, who invented the cataract, a very ingenious self-acting valve arrangement,
which is still universally used in Cornish engines. It is worth mentioning that, in 1 ?;!.">.
Leopold invented an engine in which steam of a higher pressure than that of the atmos-
phere was employed in the cylinder, but his engine possessed defects that prevented its
practical use.

The next essential improvements on the steam-engine were those of Watt, which
began a new era in the history of steam-power. The first and most important improve-
ment made by Watt was the separate condenser, patented in 17(50. lie had observed
that the jet of cold water thrown into the cylinder to condense the steam, m -eosarily
reduced the temperature of the cylinder so much that a great deal of the steam flowing
in at each upward stroke of the piston was condensed before the cylinder got back the
heat abstracted from it by the spurt of cold water used for condensing the steam in th
cylinder. The loss of steam arising from this was so great that only about one-fourth of
what was admitted into the cylinder was actually available as motive-power. Wan.
therefore, provided a separate vessel in which. to condense the steam, and which oould

FIG. 1.

Steam.

794

be kept constantly in a state of vacuum, without the loss which arose when the cylinder
itself was used as a condenser. This device, which now looks simple enough, was the
greatest of Watt's inventions, and forms the foundation of his fume. His genius waa
such that in a few years he changed the steam-engine from a clumsy, wasteful, almost
impracticable machine into a machine practically the same as we now have. The prin-
cipal improvements since his time have been either iu matters relating to the boiler; in
details of construction consequent on our increased facilities, improved machinery, and
greater knowledge of the strength of materials; in the enlarged application of his princi-
ple of expansive working; or in the application of the steam-engine to the propulsion of
carriages and vessels. His principal inventions were: 1. The condensation of steam in
a vessel separate from the cylinder, so as to avoid the cooling of the latter; 2. The use
of a pump, called an "air-pump," to withdraw the condensed water, and mixed steam
and air, from the condenser; 3. To surround the cylinder either with a steam-jacket,
or with some non-conducting body, in order to prevent radiation of heat (these three,
with others, were included in the specification of 1769); 4. To use the steam expansively
in the way explained further on in this article (this was invented before 170)9. but not
published till 1782); and 5. The now universally used double-acting engine, and the con-
version of the reciprocating motion of the beam into a rotary motion* by means of a
crank (both these were invented before 1778, the engine being patented in 1782. but the
crank Laving before that date been pirated and patented by another). In 1784 Watt also
patented and published his' parallel motion, throttle-valve, governor, and indicator; all
four of which are in substance still used.

It would be inconsistent with our limits to enter .into any description of the construc-
tive details of steam-engines; we can only afford to give a general notion of the way in
which the motion is originated, and to explain the chief principles on which the motive-
power and economy of engines depend. -We shall consider the latter first, and may say
that I he article STEAM should be read as an introduction to what follows, as we must
assume a familiarity with the statements there made.

The common mode of employing steam in an engine is by causing it to press alter-
nately on the two surfaces of a movable diaphragm or piston inclosed in a fixed, steam-
tight, cylindrical box. In fig. 2, A is the piston, and B a
section of the box. The piston, by means of a rod E,
passing through the end of the box, is made to communi-
cate motion to the rest of the machinery. The steam is
first admitted to one end of the cylinder 'through an open-