SYMINGTON’S IMPROVED ATMOSPHERIC STEAM ENGINE

In 1787 William Symington patented his invention of

“A STEAM ENGINE, ON PRINCIPLES ENTIRELY NEW.”

In 1767 James Watt took out a patent for "A New Invented Method of Lessening the Consumption of Steam and Fuel in Fire Engines." Watt's invention of the separate condenser improved the efficiency of the Newcomen engine. By an Act of Parliament, Watt's patent was extended by twenty-five years.

William Symington devised a method which would circumvent Watt's patent for the separate condenser. His novel design was an ingenious adaptation of the Newcomen engine. An opening in the the base of the sylinder was occupied by a small piston which served as a valve and a pump which directed condensate and steam into a condensing chamber below the cylinder. Watt believed that the Symington design infringed his patent. However, he felt that the Symington engine would be expensive to produce and would not constitute a threat.

Symington's invention was a condensing beam engine in which the main cylinder was combined with an air pump and condenser. There was a free piston called the 'Medium', below the usual working piston. The Medium was balanced by a rod passing through the cylinder bottom and articulating with a counter-weighted lever. Steam was admitted under pressure between the pistons during the upward stroke of the power piston. The medium was brought down, clearing the space below it of air and condensate. At the end of the idle stroke, the lower piston was raised, allowing the egress of steam which was condensed in the chamber beneath the cylinder.

The upper part of the cylinder, within the stroke of the power piston, was kept hot by flue gases from the boiler furnace and no sealing water was used above the power piston. Rotary motion could be achieved by racks and chains attached to the beam which drove a set of ratchet wheels. Steam was transferred from above to below the Medium piston by transfer valves in the latter. This probably proved unsatisfactory for it was abandoned in later and larger engines in favour of an external valve.

William Symington signed and sealed the original document, described as a "deed poll", on 27 June 1787. His signature was witnessed by Gilbert Meason and Adam Grieve. Meason was an Edinburgh businessman who was the managing partner of the Wanlockhead Mining Company. He was a great supporter of William Symington whom he sponsored to attend Edinburgh University. The deed poll was sworn before the advocate James Veitch 1712-1793 of Elioch who was Meason's neighbour in St. Andrew Square, Edinburgh.

The specification has been transcribed on to a parchment roll which may be found in the National Archive at Kew, to which his three original drawings are attached. ^[1]

^[1] Patent 1610 William Symington 1787, Chancery: Petty Box Office: Specification and Surrender Rolls 17 November 1786-17 August 1787 NA C210/30

Figure "No. 1^st General Section of William Symington’s Steam Engine"

Legend to this drawing from the text of the patent specification:

AA the medium

b counterweight

c beam

d valve in the medium

e e openings at base of cylinder G

f f piston

G cylinder

h spiral flue surrounding the cylinder

WILLIAM SYMINGTON'S 1787 PATENT SPECIFICATION FOR A STEAM ENGINE, ON PRINCIPLES ENTIRELY NEW

A. D. 1787 . . . . . . . No 1610.

Steam Engine.

SYMINGTON’S SPECIFICATION.

TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM SYMINGTON, of Wanlock Head, in the Parish of Sanquhar, in the County of Dumfries, North Britain, send greeting.

WHEREAS I, the said William Symington, did, by my petition, humbly represent unto His Majesty, that after much study I had invented “A STEAM ENGINE, ON PRINCIPLES ENTIRELY NEW,” which I apprehended would be of great public utility; that I was the first and true Inventor thereof, and the same is not known to or practised by any other person or persons, to the best of my knowledge or belief; I therefore most humbly prayed His Majesty that he would be graciously pleased to grant to me, my executors, administrators, and assigns, His Majesty’s Royal Letters Patent under the Great Seal of Great Britain, for the sole benefit and advantage of my said Invention within England, and His Dominion of Wales and Town of Berwick upon Tweed, for the term of fourteen years, pursuant to the Statute of that case made and provided: And whereas by the said Letters Parent under the Great Seal of Great Britain, bearing date of the Fifth day of June, in the twenty-seventh year of the reign of His said Majesty, after reciting the said petition, and also reciting that His Majesty, being willing to give encouragement to all arts and inventions that might be for the public good, was graciously pleased to condescend to my request, His Majesty, of His especial grace, certain knowledge, and meer motion, did, for Himself, His heirs and successors, give and grant unto me, the said William Symington, my executors, administrators, and assigns, His special licence, full power, sole privilege and authority, that I, the said William Symington, my executors, administrators, and assigns, and every of them, by myself or themselves or by my or their deputy or deputy’s, servants or agents, or such others as I, the said William Symington, my executors, administrators, and assigns, should at any time agree with, and no others, from time to time and at all times during the term of years therein expressed, should and lawfully might make use, exercise, and vend my said Invention within that part of His Majesty’s Kingdom of Great Britain called England, His Dominion of Wales, and Town of Berwick upon Tweed, in such manner as to me, the said William Symington, my executors, administrators, and assigns, or any of them, should in my or their discretions seem meet; and that I, the said William Symington, my executors, administrators, and assigns, should and lawfully might have and enjoy the whole benefit, commodity, and advantage, from time to time coming, growing, accruing and arising by reason of the said Invention for and during the term of years therein mentioned; to have, hold, exercise, and enjoy the said licence, powers, priviledges, and advantages therein-before granted or mentioned to be granted unto me, the said William Symington, my extors, administrators, and assigns, for and during and unto the full end and term of fourteen years from the date of the said Letters Patent next and immediately ensuing, and fully to be compleat and ended, according to the statute in such case made and provided; in which said Letters Patent is contained a proviso, that if I, the said William Symington, should not particularly describe and ascertain the nature of my said Invention, and in what manner the same is to be performed, by an instrument in writing under my hand and seal, and cause the same to be enrolled in His Majesty’s High Court of Chancery within one calendar month next and immediately after the date of those His Majesty’s Letters Patent, that then His said Majesty’s Letters Patent, and liberties and advantages whatsoever thereby granted, should utterly cease, determine, and become void, any thing therein-before contained to the contrary, thereof in anyways notwithstanding.

NOW KNOW YE, that I, the said William Symington, in compliance with the said provisoe, do hereby describe and ascertain the nature of my said Invention, in manner following, that is to say:

The several Drawings delineated, and herewith produced and subscribed by me as relative thereunto, and marked with the Figures 1, 2, and 3, are so many sections, in which are displayed the use of the machinery in my method of separating the steam from the water, tho’ in the same cylinder, combining the steam and atmosphere pressures, expelling from the cylinder the water, air, or any other incondensible bodies which may be collected therein while the engine is working, and in heating the cylinder externally, and not by means of steam; the particulars of which they consist being as follows, vizt, first, by condensing the steam within the same cylinder, marked G, in section No 1, and not cooling it in that place where the powers of the steam are to be made use of when in a rarified state by having what I call a medium marked A, A, in section No 1, (which medium will be made of iron or other solid bodies,) fitted in the cylinder, and made so close, by means of stuffing or otherwise, that neither the water which remains below the medium in the cylinder can act so immediately upon the steam as to condense it at an improper time, nor the steam above warm the water below the medium so much as to render it incapable to assist the water that may be jetted into the cylinder to condense the steam when wanted. This medium, while the engine is at work, is made to rise and fall by means of the engine or otherwise; but the common way in which it will be wrought will be by a weight marked (b) in section No 1, or balance, which will act upon a beam marked C, in section No 1, connected with a moveable rod, which comes down from the medium to the bottom of the cylinder, which, as soon as the pressure of the steam is taken from above it, or the steam allowed to pass thro' it, which is done by opening a valve marked d, in section No 1, (placed in it for that purpose,) then the said balance or engine shall raise the medium out of the water contained in the bottom of the cylinder so as to expose the steam to the surface of that water, which will be twice the diameter of that part of the cylinder into which the steam is admitted above the medium, so that it may more readily assist the water jetting in to condense the steam. After the steam is thus condensed, the valve in this medium, before the steam is allowed to enter the cylinder again, is shut, so that after the steam comes into the cylinder it acts with such force upon the top of the medium as to depress it, and cause expell from the bottom of the cylinder, through openings marked (e, e) section No 1, made for that purpose, as much water as was jetted into the cylinder during the stroke of the engine alongst with the air or any other incondensible bodies that may be collected therein. Secondly, by loading the piston marked f, f, in section No 1, with so much more weight than the pump rods, or what may be applyed to the out end of the great lever, can counterbalance as the power of the steam, which, when the engine is fully burdened, may press upon the piston, or what may be used in place of it, with a force of not less than equal to two pounds weight for every square inch of surface contained in that moveable part exposed to the steam, can raise. Thirdly, in having that vessel commonly called the cylinder heated externally, not by steam, but, as soon as the flue marked h in section No 1, quits the boiler, by leaving the whole or a part of it in a spiral direction round its cylinder. Fourthly, I intend using a boiler, by part of which the fireplace is formed. Fifthly, when rotatory motions of whatever kind are wanted, two ratchet wheels, such as are marked i, i, in Section No 3, will be placed upon two or the same axis in such manner that the engine turns forward the one wheel, the other will be reversed without impeding the motion or diminishing the power, so as to be ready to carry on the motion by the time the other wheel begins to be reversed. These ratchet wheels will be turned by two rack rods, marked k, k, in section No 3, and weight marked O, which will be connected to the engine or otherwise. When a double engine is applied, two pulley wheels may be made use of instead of the ratchet wheels, and chains or some other flexible substance adapted in place of the rack rods.

In witness whereof, I, the said William Symington, have hereunto set my hand and seal, the Twenty-seventh day of June, in the twenty-seventh year of the reign of our Sovereign Lord George the Third, by the grace of God, of Great Britain, France, and Ireland King, Defender of the Faith, &c., and in the year of Our Lord One thousand seven hundred and eighty-seven.

WILLIAM (L.S.) SYMINGTON.

Signed, sealed, and delivered by the within-named William Symington, in the presence of

GILBT MEASON.

ADAM GRIEVE.

This is the deed Poll to which the after-mentioned affidavit refers.

JA. VEITCH, J.P.

BE IT REMEMBERED, that it appears to the Court of Our Lord the King, in His Chancery at Westminster, by an affidavit in the following words (that is to say):-

Adam Grieve, of the City- of Edinburgh, in North Britain, Gentleman, maketh oath and sayeth, that he did see William Symington, in the Deed Pole annexed, sign and seal and as his act and deed deliver the said Deed Poll, with three sections of the steam engine mentioned in said Deed Poll, marked 1^st, 2d, and 3d, and each signed by the said William Symington, as referred to by the said Deed Poll, in the presence of Gilbert Meason, of the City of Edinburgh aforesaid, Gentleman, and of this deponent; and that the names William Symington appearing to be set and subscribed at the foot of the said Deed Poll as the party executing the same, and Gilbert Meason and Adam Grieve indorsed on the back thereof as witnesses attesting the due execution of the same, are of the respective hands….

The patent specification number 1610 is illustrated by three coloured drawings: ^[1]

No. 1^st

General Section of William Symington’s Steam Engine

On the reverse of which is inscribed:

Edinburgh 27 June 1787. This is the Section No. 1^st. of the Steam Engine mentioned in an Instrument in my writing under my hand and seal of this date

William Symington

No. 2

Inside front view, of William Symington’s Steam engine

On reverse:

Edinburgh 27 June 1787 This is the Section No. 2d. of the steam engine mentioned in an instrument in writing under my hand and seal of this date

William Symington

No. 3d.

A section of a method of applying the Power of the Steam Engine to Rotatory motion

ii Ratchet Wheel

nn a piece of wood or other bodies to which the Ratchet Wheels are connected by means of the catches such as marked p

l the common axis to which any wheel may be joined

o the weight for moving the Ratchet wheel covered by n.n.

M, a piece of the engine beam

R, a guide Post

On reverse:

Edinburgh 27 June 1787 This is the Section No. 3d. of the Steam Engine Mentioned in an instrument in writing under my hand and seal of this date

William Symington

^[1] NA C210 /30

DESCRIPTION OF WILLIAM SYMINGTON’S 1787 PATENT ATMOSPHERIC ENGINE

The patent specification reveals Symington’s method of separating the steam in the working cylinder from the cylinder base where the steam was condensed and from which waste products were expelled.

Fundamental to the invention was a condensing device integrated within the base of the cylinder and separated from the working cylinder by a second piston which Symington termed a "medium."

The working mechanism is illustrated in the figures which accompany the patent application.

The engine cylinder illustrated has a 48 inch bore and 8 foot stroke. The floor of the main cylinder is occupied by a second piston, the “medium,” which separated the working cylinder from an extension to the cylinder where the steam was condensed. The function of the medium was to direct steam from the working cylinder into a compartment where the steam was condensed and then expelled by the plunging movement of the medium.

The medium was a watertight structure with a central valve which controlled the egress of steam from the main cylinder. In the patent drawing, the medium is depicted as a chambered iron cylinder; flanges reduce the area of contact with the wall of the cylinder. The colouring of the medium suggests that the upper and lower surfaces were made of wood. The valve rod moves in the axis of the medium. The upper margin is cut away so as not to obstruct the ingress of steam into the main cylinder.

The base of the cylinder below the medium is immersed in a tank of water where the diameter is extended to twice the diameter of the working cylinder to facilitate heat exchange. Cold water was injected and directed towards the base of the medium through two nozzles during the working stroke of the engine.

The working cylinder was encased by a spiral flue which was bricked in and which led direct from the boiler.

MODE OF OPERATION OF THE 1787 STEAM ENGINE

The rise and fall of the medium and the operation of its valve was coordinated with the motion of the main piston. ^[1]

Steam was admitted to the working cylinder below the piston from the boiler with the medium down and the medium valve closed.

When the main piston was fully raised, the medium was lifted and the medium valve opened; steam in the cylinder was directed through valve in the medium into the condensing chamber below the medium and exposed to cold water which was injected under the medium during the working stroke of the engine.

When the working piston had descended, the valve in the medium was closed and the medium forced down. Steam and condensate were expelled from openings in the lower chamber by the plunging medium which thus operated as an air pump.

With the medium down, steam from the boiler was again allowed to again enter the working cylinder.

The motion of the medium and operation of the valve in the medium was controlled by a system of levers linked to the main overhead beam of the engine.

The patent drawings illustrate the mechanism controlling the valve in the medium.

A valve rod passed down through the central axis of the medium and was operated by a counterbalanced horizontal beam which linked in turn to the main engine beam overhead. This mechanism served to operate the valve and also to pull the medium down as the valve closed.

The rise and fall of the medium was also controlled by a counterbalanced beam mechanism. A connecting rod from the medium extended through the base of the cylinder and was operated by the movement of the beam marked c in Figure 1. The medium was counterbalanced by the weight marked b and was lifted by the counterweight after the steam had passed through the open valve.

However, Figure 1 appears to define the mechanism for the valve rod, whereas the arrangement for the piston rod of the medium is left to the imagination.

Heating of the cylinder

The cylinder was heated externally, not by steam but by hot air from a flue (marked h in Figure 1 and also well shown in Figure 3), which exited the boiler and was directed in a spiral course around the cylinder of the steam engine.

Method of obtaining Rotatory Motion

Rotatory motion was achieved by using a system of two ratchet wheels placed back to back on the same axis (marked i, i in Figure 3) and turned by rack rods (k, k).

For a double cylinder engine (as employed in the Dalswinton boat), pulley wheels would be used in place of ratchet wheels and chains adapted in place of rack rods.

The patent specification and drawings indicate that the medium and the valve are each operated by levers and counterweights, driven by the main beam and controlled by a catch device on a wheel. The placement of the valve within the structure of the medium itself proved unsatisfactory and was later abandoned for an external valve.

John Farey, in his classic "Treatise on the Steam Engine, historical, practical, and descriptive", published in 1827, offered the following explanation of the mode of action of the Symington Engine: ^[1]

The operation of Mr. Symington's engine was the same as that of Mr. Watt's single engine. Suppose the working piston to be at the top of its cylinder, and the lower piston to be raised to its highest position, so as to be on a level with the passage leading into the lower part of the cylinder; suppose the cylinder to be full of steam, and the space beneath the lower piston to be exhausted, as well as the condenser adjoining to it. The valve by which strain is admitted from the boiler into the cylinder bring shut, let the exhausting valve be opened, and also a small valve to admit an injection of cold water into the condenser at the bottom of the cylinder; the steam will then by its own elasticity pass out from the cylin­der, through the exhausting valve and eduction pipe, into the condenser, where it will be condensed by the injection as fast as it arrives. The space in the cylinder, beneath the working piston, being thus exhausted, the pressure of the atmosphere on that piston will force it down into the cylinder, and make the working stroke. The lower piston, by its connexion with the great lever, is forced down at the same time, with one eighth of the motion of the working piston, whereby any water or air, which is contained in the bottom of the cylinder, beneath the lower piston, will be expelled out of that space, and discharged through the discharge valve into the open air, or into a hot well.

The working stroke being thus completed, the exhausting valve and the injection valve are shut, and the steam valve is opened, to admit fresh steam from the boiler into the cylinder above the lower piston, and beneath the working piston ; this allows the working piston to be raised up again by its counterweight, and the lower piston is raised at the same time, by its lever; in so doing it leaves an exhausted space beneath it, in the bottom of the cylinder, into which the water recently injected into the condenser drains through the foot valve into the bottom of the cylinder; and the air follows it, so as to preserve the exhaustion within that condenser.

When the piston arrives at the top of its course, the steam valve is shut, and the exhausting valve and the injection valve opened again, to make another stroke; during which the lower piston, by its descent, expels all the water and air which is contained in the space beneath it, and drives it through the discharge valve, into the hot well.

^[1] Farey, John, A Treatise on the Steam Engine, Historical, Practical, and Descriptive London 1827 pages 656-658

COMPARATIVE ENGINE TRIAL 1788

In 1788 William Symington conducted a trial in which he compared the performance of a Watt engine with an engine of his own design.

In 1779 a Boulton and Watt pumping engine with a 36 inch diameter cylinder was erected on the Margaret Vein at Wanlockhead. ^[1] George Symington, William's elder brother, was employed in the erection and maintenance of this engine and William would have closely observed the machinery as a fifteen year old lad. In 1785 the Symington brothers erected a second Watt engine on the Margaret Vein.

In the summer of 1788 William Symington converted the original 1779 Watt engine according to the design specified in his 1787 patent. The engine was old but allegedly in good repair.

In a handwritten advertisement, he reports a clear increase in power and reduced fuel consumption for the modified engine. A copy of William Symington’s statement is to be found in the papers of Lord Dundas of Kerse. (see below) ^[2] The Statement is in William Symington’s handwriting:

Statement of a comparative trial made betwixt Watt’s and Symington’s steam Engines at Wanlockhead lead mine Scotland in Summer of 1788

The engine upon which this trial was made was first erected upon Mr. Watt’s principles having a cylinder 36 inches diameter and when in good repair, wrought with a power equal to 9 ½ lib. for each square inch contained within the Piston – When converted into Symington’s principles, with equal velocity, and a consumption of fuel somewhat less, it wrought the same column of pumps so much lengthened as to increase the power to 12 lib. for each square inch contained in the Piston.

The principles of this engine render it very little more complicated than the old Fire engine, hence it can be erected at as little expence as any steam engine in use; and any person acquainted with the common one, can easily manage and keep it in repair-

From the superior advantages of this engine it will be evident to all those who make use of such machines, that to adopt it will be to their great profit, as the Inventor is enabled to give them the use of it upon more advantageous terms than any hitherto offered to the Public-

Any Person interested in this business may be more particularly informed by applying to “Mr. William Symington Engineer at Wanlockhead by Sanquhar” N. Britain

Messrs. Symington & Taylor

No. 67 Strand

John Taylor, mine manager at Wanlockhead was a partner in their venture.

This advertisement attracted the attention of James Watt who considered the Symington design as an infringement on his own patent. The Boulton and Watt Collection which is held in the Birmingham Reference Library contains a folder on Symington engines under the heading "Pirate engines." ^[3] See the chapter on Symington engines.

^[1] Scotland W. Harvey & G. Downs-Rose, The Bay Mine Wanlockhead, Scotland A Monograph of The Northern Mine Research Society 1976

^[2] NAS RH4/203/2, Number 27 (North Riding Record Office ZNK X 2/12/27) Papers of Thomas Dundas of Kerse, later Thomas, First Lord Dundas 1779-1793

^[3] BRL MS3147/5/1353b

1787 PATENT ENGINE PROSPECTUS

A prospectus was issued for Mr. Symington’s 1787 Patent Engine ^[1]

Symington’s Patent Steam Engine.

William Symington having erected last summer one of his Patent Steam Engines at the Wanlockhead mines, the superiority of which being fully established it may be proper to announce its advantages.

Its power is equal to twelve pounds upon each square inch of the piston, yet by this increased power the consumption of fuel is not greater than that of the Improved Steam Engines at present used. In simplicity it approaches the Old Engine, the open cylinder and atmospheric pressure being retained and the air and hot water pumps, separate condensing vessels, etc, laid aside. It is from the simple manner by which condensation is affected that it derives its greatest advantage.

Hence the Inventor is confident that, from the simplicity and increased power of his Steam Engine it can be worked at less expense than others and will be found subject to fewer interruptions.

The engine by the Inventor’s new rotatory motion can be applied with peculiar advantage to the purposes of grinding, sawing, etc.

NB. At little more expense than the cost of a new cylinder, steam engines on other constructions can be converted into Symington’s engine.

Letters addressed to William Symington, Engineer, Wanlockhead, by Edinburgh, will be punctually attended to.

^[1] North Yorkshire County Record Office ZNK.X2/15/7 (Zetland/Dundas Family archive)

ADVERTISEMENT FOR THE 1787 PATENT ENGINE

William Symington had the following advertisement published in the press:

Newcastle Courant 24 January 1789 page 3

NEW PATENT STEAM ENGINE.

WILLIAM SYMINGTON, having completed his Experiments upon his new, improved Steam Engine, and last summer having erected one, with a 36 inch cylinder, upon the Lead Mines at Wanlockhead, in Scotland, finds its properties to be as follows

1^st, Acting by the pressure of the atmosphere, it works with a power equal to 12 lib. For each square inch contained in the pistons and, when thus loaded, can with ease perform 14 strokes, each stroke 8 feet long, per minute.

2d, By a new, but simple, method of condensation, this power is produced, without alternately heating and cooling the cylinder, as in the old Engine.

3d, Its consumption of Coal is as little as that of any other steam Engine whatever.

4^th, Being little more complicated than the common Fire Engine, it can be as easily managed; and, at as little expence, kept in repair.

5^th, From the nature of its construction, Engines, erected on the principles of the old one, can be converted to those of the above plan, at little more than the expence of a small addition to the bottom of their present cylinders.

6^th, Being aided by this new and very advantageous method of applying the power of the Engine to rotatory motions, it can with more advantage and conveniency be adapted for the purposes of drawing Coals from deep works, grinding, sawing, &c. than any other Steam Engine yet known to the public.

Hence the Inventor recommends it to the attention of the Gentlemen who have occasion to use such Machines, as, with confidence, he can assure them that this Engine possesses very great advantages over any other yet in use, and, when adopted, will shew itself to be of public utility.

Letters addressed to "Mr William Symington, Engineer, Wanlockhead, by Edinburgh," will be duly attended to.