Watt Improves The Steam-Engine

Author:      Arago, Francois

Watt Improves The Steam-Engine

 

1769

 

 

     No greater service has been rendered to the world through mechanical

invention than that performed by James Watt in his improvement of the

steam-engine.  Watt was born at Greenock, Scotland, in 1736.  During the

eighty-three years of his life much progress was made in mechanics and

engineering in different countries, but the name of Watt remains the most

brilliant among contemporary workers in these departments of practical

science.

 

     The first contriver of a working steam-engine is supposed to have been

Edward, second Marquis of Worcester (1601-1667).  No complete description of

his engine is known to exist, and conjectures about it disagree; but it is not

questioned that he made important contributions to the great invention, upon

which others at the same time were engaged.  The construction of the first

actual working steam-engine is usually credited to Thomas Savery, born in

England about 1650.  He devised a "fire-engine," as he called it, for the

raising of water, but, owing to the want of strong boilers and a suitable form

of condenser, it imperfectly served its purpose, and was soon superseded by

the better engine of Thomas Newcomen, here referred to by Arago.

 

     Newcomen was an English inventor, born in 1663.  With Savery and Cawley,

he invented and in 1705 patented the atmospheric steam-engine by which he is

known, and which, as told by Arago, gave place to the superior invention of

Watt.

 

     Arago was an eminent French physicist and astronomer (1786-1853), who is

even better known through his biographies of other great workers in science.

His account of "the fruitful inventions which will forever connect the name of

Watt with the steam-engine" is all the more valuable for preservation because

written while the steam-engine" was still in an early stage of its

development.  Of its later improvements and varied uses, numerous descriptions

are within easy reach of all readers.

 

     In physical cabinets we find a good many machines on which industry had

founded great hopes, though the expenses of their manufacture or that of

keeping them at work has reduced them to be mere instruments of demonstration.

This would have been the final fate of Newcomen's machine, in localities at

least not rich in combustibles, if Watt's efforts had not come in to give it

an unhoped - for degree of perfection.  This perfection must not be considered

as the result of some fortuitous observation or of a single inspiration of

genius; the inventor achieved it by assiduous labor, by experiments of extreme

delicacy and correctness.  One would say that Watt had adopted as his guide

that celebrated maxim of Bacon's: "To write, speak, meditate, or act when we

are not sufficiently provided with facts to stake out our thoughts is like

navigating without a pilot along a coast strewed with dangers or rushing out

on the immense ocean without compass or rudder."

 

     In the collection belonging to the University of Glasgow there was a

little model of a steam-engine by Newcomen that had never worked well.  The

professor of physics, Anderson, desired Watt to repair it.  In the hands of

this powerful workman the defects of its construction disappeared; from that

time the apparatus was made to work annually under the inspection of the

astonished students.  A man of common mind would have rested satisfied with

this success.  Watt, on the contrary, as usual with him, saw cause in it for

deep study.  His researches were successively directed to all the points that

appeared likely to clear up the theory of the machine.  He ascertained the

proportion in which water dilates in passing from a state of fluidity into

that of vapor; the quantity of water that a certain weight of coal can convert

into vapor; the quantity and weight of steam expended at each oscillation by

one of Newcomen's engines of known dimensions; the quantity of cold water that

must be injected into the cylinder to give a certain force to the piston's

descending oscillation; and finally the elasticity of steam at various

temperatures.

 

     Here was enough to occupy the life of a laborious physicist, yet Watt

found means to conduct all these numerous and difficult researches to a good

termination, without the work of the shop suffering thereby.  Dr. Cleland

wished, not long since, to take me to the house, near the port of Glasgow,

whither our associate ^1 retired, on quitting his tools, to become an

experimenter.  It was razed to the ground!  Our ranger was keen but of short

duration.  Within the area still visible of the foundations ten or twelve

vigorous workmen appeared to be occupied in sanctifying the cradle of modern

steam-engines; they were hammering with redoubled blows various portions of

boilers, the united dimensions of which certainly equalled those of the humble

dwelling that had disappeared there.  On such a spot, and under such

circumstances, the most elegant mansion, the most sumptuous monument, the

finest statute, would have awakened less reflection than those colossal

boilers.

 

[Footnote 1: Watt was one of the eight foreign associates of the French

Academy of Sciences, which body Arago was addressing. - Ed.]

 

     If the properties of steam was present to your mind, you will perceive at

a glance that the economic working of Newcomen's engine seems to require two

irreconcilable conditions.  When the piston descends, the cylinder is required

to be cold, otherwise it meets some steam there, still very elastic, which

retards the operation very much, and diminishes the effect of the external

atmosphere.  Then, when steam at the temperature of 100 degrees flows into the

same cylinder and finds it cold, the steam restores its heat by becoming

partially fluid, and until the cylinder has regained the temperature of 100

degrees its elasticity will be found considerably attenuated; thence will

ensue slowness of motion, for the counterpoise will not raise the piston until

there is sufficient spring contained in the cylinder to counterbalance the

action of the atmosphere; thence there will also arise an increase of expense.

 

     No doubt will remain on the immense importance of this economical

observation, when I shall have stated that the Glasgow model at each

oscillation expended a volume of steam several times larger than that of the

cylinder.  The expense of steam, or, what comes to the same thing, the expense

of fuel, or, if we like it better, the pecuniary cost of keeping on the

working of the machine, would be several times less if the successive heatings

and coolings, the inconveniences of which have just been described, could be

avoided.

 

     This apparently insolvable problem was solved by Watt in the most simple

manner.  It sufficed for him to add to the former arrangement of the engine a

vessel totally distinct from the cylinder, and communicating with it only by a

small tube furnished with a tap.  This vessel, now known as "the condenser,"

is Watt's principal invention.

 

     Still another invention by Watt deserves a word, the advantages of which

will become evident to everybody.  When the piston descends in Newcomen's

engine, it is by the weight of the atmosphere.  The atmosphere is cold; hence

it must cool the sides of the metal cylinder, which is open at the top, in

proportion as it expands itself over the entire surface.  This cooling is not

compensated during the whole ascension of the piston, without the expense of a

certain quantity of steam.  But there is not loss of this sort in the engines

modified by Watt.  The atmospheric action is totally eliminated by the

following means:

 

     The top of the cylinder is closed by a metal cover, only pierced in the

centre by a hole furnished with greased tow stuffed in hard, but through which

the rod of the piston has free motion, though without allowing free passage

either to air or steam.  The piston thus divides the capacity of the cylinder

into two distinct and well-closed areas.  When it has to descend, the steam

from the caldron reaches freely the upper area through a tube conveniently

placed, and pushes it from top to bottom as the atmosphere did in Newcomen's

engine.  There is no obstacle to this motion, because, while it is going on,

only the base of the cylinder is in communication with the condenser, wherein

all the steam from that lower area resumes its fluid state.  As soon as the

piston has quite reached the bottom, the mere turning of a tap suffices to

bring the two areas of the cylinder, situated above and below the piston, into

communication with each other, so that both shall be filled with steam at the

same degree of elasticity; and the piston being thus equally acted upon,

upward and downward, ascends again to the top of the cylinder, as in

Newcomen's atmospheric engine, merely by the action of a slight counterpoise.

 

     Pursuing his researchers on the means of economizing steam, Watt also

reduced the result of the refrigeration of the external surface of the

cylinder containing the piston, almost to nothing.  With this view he enclosed

the metal cylinder in a wooden case of larger diameter, filling the

intermediate annular space with steam.

 

     Now the engine was complete.  The improvements effected by Watt are

evident; there can be no doubt of their immense utility.  As a means of

drainage, then, you would expect to see them substituted for Newcomen's

comparatively ruinous engines.  Undeceive yourselves: the author of a

discovery has always to contend against those whose interest may be injured,

the obstinate partisans of everything old, and finally the envious.  And these

three classes united, I regret to acknowledge it, form the great majority of

the public.  In my calculation I even deduct those who are doubly influenced

to avoid a paradoxical result.  This compact mass of opponents can only be

disunited and dissipated by time; yet time is insufficient; it must be

attacked with spirit and unceasingly; our means of attack must be varied,

imitating the chemist in this respect - he learning from experience that the

entire solution of certain amalgams requires the successive application of

several acids.  Force of character and perseverance of will, which in the long

run disintegrate the best woven intrigues, are not always found conjoined with

creative genius. In case of need, Watt would be a convincing proof of this.

His capital invention - his happy idea on the possibility of condensing steam

in a vessel separate from the cylinder in which the mechanical action goes on

- was in 1765.

 

     Two years elapsed without his scarcely making an effort to apply it on a

large scale.  His friends at last put him in communication with Dr. Roebuck,

founder of the large works at Carron, still celebrated at the present day. The

engineer and the man of projects enter into partnership; Watt cedes two-thirds

of his patent to him.  An engine is constructed on the new principles; it

confirms all the expectations of theory; its success is complete.  But in the

interim Dr. Roebuck's affairs receive various checks. Watt's invention would

undoubtedly have restored them; it would have sufficed to borrow money; but

our associate felt more inclined to give up his discovery and change his

business.  In 1767, while Smeaton was carrying on some triangulations and

levellings between the two rivers of the Forth and the Clyde, forerunners of

the gigantic works of which the part of Scotland was to be the theatre, we

find Watt occupied with similar operations along a rival line crossing the

Lomond passage.  Later he draws the plan of a canal that was to bring coals

from Monkland to Glasgow, and superintends the execution of it.  Several

projects of a similar nature, and, among others, that of a navigable canal

across the isthmus of Crinan, which Rennie afterward finished; some deep

studies on certain improvements in the ports of Ayr, Glasgow, and Greenock;

the construction of the Hamilton and Rutherglen bridges; surveys of the ground

through which the celebrated Caledonian Canal was to pass, occupied our

associate up to the end of 1773.  Without wishing at all to diminish the merit

of these enterprises, I may be permitted to say that their interest and

importance were chiefly local, and to assert that neither their conception,

direction, nor execution required a man called James Watt.

 

     In the early part of 1774, after contending with Watt's indifference, his

friends put him into communication with Mr. Boulton, of Soho, near Birmingham,

an enterprising, active man, gifted with various talents.  The two friends

applied to Parliament for a prolongation of privilege, since Watt's patent,

dated 1769, had only a few more years to run.  The bill gave rise to the most

animated discussion.  The celebrated mechanic wrote as follows to his aged

father: "This business could not be carried on without great expense and

anxiety.  Without the aid of some warm-hearted friends we should not have

succeeded, for several of the most powerful in the House of Commons were

opposed to us." It seemed to me interesting to search out to what class of

society these Parliamentary persons belonged to whom Watt alluded, and who

refused to the man of genius a small portion of the riches that he was about

to create.  Judge of my surprise when I found the celebrated Burke at their

head.  It is possible, then, that men may devote themselves to deep studies,

possess knowledge and probity, exercise to an eminent degree oratorical powers

that move the feelings, and influence political assemblies, yet sometimes be

deficient in plain common-sense?  Now, however, owing to the wise and

important modifications introduced by Lord Brougham in the laws relative to

patents, inventors will no longer have to undergo the annoyances with which

Watt was teased.

 

     As soon as Parliament had granted a prolongation of twenty-five years to

Watt's patent, he and Boulton together began the establishments at Soho, which

have become the most useful school in practical mechanics for all England.

The construction of draining-pumps of very large dimensions was soon

undertaken there, and repeated experiments showed that, with equal effect,

they saved three-quarters of the fuel that was consumed by Newcomen's previous

engines.  From that moment the new pumps were spread through all the mining

counties, especially in Cornwall.  Boulton and Watt received as a duty the

value of one-third of the coal saved by each of their engines.  We may form an

opinion of the commercial importance of the invention from an authentic fact:

in the Chace-water mine alone, where three pumps were at work, the proprietors

found it to their advantage to buy up the inventor's rights for the annual sum

of sixty thousand francs (two thousand four hundred pounds).  Thus in one

establishment alone, the substitution of the condenser for internal injection

had occasioned an annual saving in fuel of upward of one hundred eighty

thousand francs (seven thousand pounds).

 

     Men are easily reconciled to paying the rent of a house or the price of a

farm.  But this good-will disappears when an idea is the subject treated of,

whatever advantage, whatever profit, it may be the means of procuring. Ideas!

are they not conceived without trouble or labor?  Who can prove that with time

the same might not have occurred to everybody?  In this way days, months, and

years of priority would give no force to the patent!

 

     Such opinions, which I need not here criticise, had obtained a footing

from mere routine as decided.  Men of genius, the "manufacturers of ideas," it

seemed, were to remain strangers to material enjoyments; it was natural that

their history should continue to resemble a legend of martyrs!

 

     Whatever may be thought of these reflections, it is certain that the

Cornwall miners paid the dues that were granted to the Soho engineers with

increased repugnance from year to year.  They availed themselves of the very

earliest difficulties raised by plagiarists, to claim release from all

obligation.  The discussion was serious; it might compromise the social

position of our associate: he therefore bestowed his entire attention to it

and became a lawyer.  The long and expensive lawsuits that resulted therefrom,

but which they finally gained, would not deserve to be now exhumed; but having

recently quoted Burke as one of the adversaries to our great mechanic, it

appears only a just compensation here to mention that the Roys, Mylnes,

Herschels, Delucs, Ramsdens, Robisons, Murdocks, Rennies, Cummings, Mores,

Southerns, eagerly presented themselves before the magistrates to maintain the

rights of persecuted genius.  It may be also advisable to add, as a curious

trait in the history of the human mind, that the lawyers - I shall here

prudently remark that we treat only of the lawyers of a neighboring country -

to whom malignity imputes a superabundant luxury in words, reproached Watt,

against whom they had leagued in great numbers, for having invented nothing

but ideas.  This, I may remark in passing, brought upon them before the

tribunal the following apostrophe from Mr. Rous: "Go, gentlemen, go and rub

yourselves against those untangible combinations, as you are pleased to call

Watt's engines; against those pretended abstract ideas; they will crush you

like gnats, they will hurl you up in the air out of sight!"

 

     The persecutions which a warm-hearted man meets with, in the quarters

where strict justice would lead him to expect unanimous testimonies of

gratitude, seldom fail to discourage, and to sour his disposition.  Nor did

Watt's good-humor remain proof against such trials.  Seven long years of

lawsuits had excited in him such a sentiment of indignation, that it

occasionally showed itself in severe expressions; thus he wrote to one of his

friends: "What I most detest in this world are plagiarists!  The plagiarists.

They have already cruelly assailed me; and if I had not an excellent memory,

their impudent assertions would have ended by persuading me that I have made

no improvement in steam-engines.  The bad passions of those men to whom I have

been most useful (would you believe it?) have gone so far as to lead them to

maintain that those improvements, instead of deserving this denomination, have

been highly prejudicial to public wealth."

 

     Watt, though greatly irritated, was not discouraged.  His engines were

not, in the first place, like Newcomen's mere pumps, mere draining-pumps.  In

a few years he transformed them into universal motive powers, and of

indefinite force.  His first step in this line was the invention of a

double-acting engine (a double effet).

 

     In the engine known under this name, as well as in the one denominated

the "modified" engine, the steam from the boiler, when the mechanic wishes

it,goes freely above the piston and presses it down without meeting any

obstacle; because at that same moment, the lower area of the cylinder is in

communication with the condenser.  This movement once achieved, and a certain

cock having been opened, the steam from the caldron can enter only below the

piston and elevates it.  The steam above it, which had produced the descending

movement, then goes to regain its fluid state in the condenser, with which it

has become, in its turn, in free communication.  The contrary arrangement of

the cocks replaces all things in their primitive state, as soon as the piston

has regained its maximum height.  Thus similar effects are reproduced

indefinitely.

 

     Power is not the only element of success in industrial works. Regularity

of action is not less important; but what regularity could be expected from a

motive power engendered by fire fed by shovelfuls, and the coal itself of

various qualities; and this under the direction of a workman, sometimes not

very intelligent, almost always inattentive?  The motive steam will be more

abundant, it will flow more rapidly into the cylinder, it will make the piston

work faster in proportion as the fire is more intense.  Great inequalities of

movement then appear to be inevitable.  Watt's genius had to provide against

this serious defect.  The throttle-valves by which the steam issues from the

boiler to enter the cylinder are constantly open.  When the working of the

engine accelerates, these valves partly close; a certain volume of steam must

therefore occupy a longer time in passing through them, and the acceleration

ceases.  The aperture of the valves, on the contrary, dilates when the motion

slackens.  The pieces requisite for the performance of these various changes

connect the valves with the axes which the engine sets to work, by the

introduction of an apparatus, the principle of which Watt discovered in the

regulator of the sails of some flour-mills: this he named the "governor,"

which is now called the "centrifugal regulator." Its efficacy is such, that a

few years ago, in the cotton-spinning manufactory of a renowned mechanic, Mr.

Lee, there was a clock set in motion by the engine of the establishment, and

it showed no great inferiority to a common spring clock.

 

     Watt's regulator, and an intelligent use of the revolving principle -

that is the secret, the true secret, of the astonishing perfection of the

industrial products of our epoch; this is what now gives to the steam-engine a

rate entirely free from jerks.  That is the reason why it can, with equal

success, embroider muslins and forge anchors, weave the most delicate webs and

communicate a rapid movement to the heavy stones of a flour-mill.  This also

explains how Watt had said, fearless of being reproached for exaggeration,

that to prevent the comings and goings of servants, he would be served, he

would have gruel brought to him, in case of illness, by tables connected with

his steam-engine.  I am aware it is supposed by the generality of people that

this suavity of motion is obtained only by a loss of power; but it is an

error, a gross error: the saying, "much noise and little work," is true, not

only in the moral world, but is also an axiom in mechanics.

 

     A few words more and we shall reach the end of our technical details.

Within these few years great advantage has been found in not allowing a free

access of steam from the boiler into the cylinder, during the whole time of

each oscillation of the engine.  This communication is interrupted, for

example, when the piston has reached one-third of its course.  The two

remaining thirds of the cylinder's length are then traversed by virtue of the

acquired velocity, and especially by the detention of the steam.  Watt had

already indicated such an arrangement.  Some very good judges esteem the

economical importance of the steam-detent as equal to that of the condenser.

It seems certain that since its adoption the Cornwall engines give unhoped -

for results; that with one bushel of coal they equal the labor of twenty men

during ten hours.  Let us keep in mind that in the coal districts a bushel of

coal only costs ninepence, and it will be demonstrated that over the greater

part of England Watt reduced the price of a man's day's work, a day of ten

hours' labor, to less than a sou (one halfpenny).

 

     Numerical valuations make us appreciate so well the importance of his

inventions that I cannot resist the desire to present two more improvements. I

borrow them from one of the most celebrated correspondents of the Academy -

from Sir John Herschel.

 

     The ascent of Mont Blanc, starting from the valley of Chamounix, is

justly considered as the hardest work that a man can accomplish in two days.

Thus the maximum mechanical work of which we are capable in twice twenty-four

hours is measured by transporting the weight of our body to the elevation of

Mont Blanc.  This work or its equivalent would be accomplished by a

steam-engine in the course of burning one kilogram (two pounds) of coal. Watt

has, therefore, ascertained that the daily power of a man does not exceed what

is contained in half a kilogram (one pound) of coal.

 

     Herodotus records that the construction of the great Pyramid of Egypt

employed 100,000 men during 20 years.  The pyramid consists of calcareous

stone; its volume and its weight can be easily calculated; its weight has been

found to be about 5,900,000 kilograms (nearly 5,000 tons).  To evaluate this

weight to 38 metres, which is the pyramid's centre of gravity, it would

require to burn 8244 hectolitres of coal.  Our English neighbors have some

foundries where they consume this quantity every week.

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