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Stephenson Safety Lamp, site of
Killingworth Colliery, Killingworth Village, Tyne & Wear, UK
Stephenson Safety Lamp, site of
associated engineer
George Stephenson
date  1815
era  Georgian  |  category  Mining/Quarrying  |  reference  NZ286708
photo  from Lives of the Engineers vol 3 (1862) by Samuel Smiles
Before electricity was available, mines were lit by naked flame, exposing underground workers to the ever-present danger of gas explosion. Stephenson’s safety lamp, born from observations and experiments at Killingworth Colliery, offered a way to reduce the risk. Its production sparked dispute with Sir Humphry Davy, who developed his own lamp more or less at the same time.
By the beginning of the 19th century, increasing industrial activity in Britain meant more mines were being worked. Coal particularly was being extracted from seams of ever greater distance and depth. Killingworth Colliery near Newcastle, where George Stephenson (1781-1848) worked, had over 160km of subterranean galleries.
Before the advent of portable electric lamps in the early 20th century, miners tried various ways to illuminate their work, including using phosphorescent dried fish skin, making sparks by striking flint on steel and carrying candles or oil lamps. The danger of igniting flammable gases released during mining operations made the provision of safe lighting an urgent requirement.
The explosive potential of coal dust wasn't recognised at the time and all accidental explosions in coal mines were attributed to a gas known as firedamp (methane). Also known as carburetted hydrogen, this lighter-than-air gas is formed in the bacteriological decay of cellulose, and is common in coal deposits — coal being fossilised plant matter.
A gas-laden atmosphere can detonate in a range of concentrations of firedamp to air of between 5 and 15 percent. Its combustion in an enclosed space like a mine gallery produces the asphyxiant gases afterdamp (a mixture of nitrogen, carbon monoxide and carbon dioxide) and blackdamp, or chokedamp, containing argon, water vapour, nitrogen and carbon dioxide. The unfortunate victims of such an explosion either burned to death or suffocated.
Prompted by a tragic accident at Felling Colliery in 1812, when at least 90 men and boys were killed, safety lamps were devised independently by Irish physician Dr William Reid Clanny (1776-1850), scientist Sir Humphry Davy (1778-1829) and self-taught engineer George Stephenson. In 1813, Clanny was first to trial his lamp, with Davy and Stephenson producing theirs in 1815.
All the lamps limited the air available to the flame. The Clanny lamp relied on isolating the flame chamber between two reservoirs of water. Though innovative, it was cumbersome and required an extra person (usually a boy) to operate it.
However, the Davy and Stephenson lamps could be carried by the miners using them. Though derived by differing methods, both restricted the incoming air by using a metal shield. Davy relied on his knowledge of chemistry to carry out controlled investigations in a laboratory at the Royal Institution in London. Stephenson based his design on observation and experimentation on site, beating Davy into manufacture and leading to bitter controversy over who thought of the idea first.
Stephenson had noticed that when a candle burned in an atmosphere containing firedamp, combustion occurred at the base rather than at the tip of the flame. He discovered this by daring to hold lighted candles to a 'blower' (a jet of gas issuing from a fissure in the coal seam) in Pit A at Killingworth Colliery. He concluded that the gas would not ignite if it passed the flame at a high enough velocity.
Believing that the "burnt air" (carbon dioxide) played a part, "he conceived, that if a lamp could be made to contain the burnt air above the flame, and permit the firedamp to come in below in a small quantity, to be burnt as it came in, the burnt air would prevent the passing of explosion upwards, and the velocity of the current from below would also prevent its passing downwards." He found that the "gas will not explode through small apertures", though he was honest enough to admit he was not sure why.
In fact, the combustion of methane involves hundreds of almost instantaneous interacting and branching chemical reactions. The methane is progressively broken down into hydrogen, oxygen and hydroxyl, a free radical. If methane and air (oxygen) are present in suitable proportions, the branching reactions continue to propagate, increasing the generation of free radicals to the point of explosion. This chain reaction is stopped chemically when free radicals collide with burnt gas molecules such as carbon dioxide, or physically when they are halted by hitting any metal surface such as a fine gauze or mesh.
Nicholas Wood (1795-1865), the colliery’s head viewer (manager), worked closely with Stephenson on developing his lamp and his locomotives. The two men tested experimental versions of the lamp by supplying the flame with firedamp released from a pig’s bladder, blowing up one set of apparatus in the process. They subsequently fitted "a piece of very fine wire-gauze" into the tube between the bladder and the lamp to prevent the reservoir of firedamp exploding. In July or August 1815, Wood made working drawings of Stephenson’s lamp.
The original design had "an open top and conical shape" and consisted of a tapered glass cylinder set on a metal base. An oil chamber in the base of the lamp fed a wick held in the annulus between two tin tubes, with air admitted through the inner tube. An external sliding plate allowed the user to control the size of the air inlet. The lamp body was sheathed in metal with a rectangular opening to let out light. It was carried inside a case with a similar window, so that the light showing could be varied, and its lid was pierced with small holes.
The prototype lamp was ordered in late September or early October 1815, from local manufacturers Michael & Jas Hogg pewterers, braziers and tinplate workers of 68 Side, Newcastle. The glass was made by the Northumberland Glass House (Company) of Lemington. The design showed an air inlet tube with a diameter of 4.75mm, though Hogg maintained that the lamp wouldn't burn unless it was 12.7mm in diameter. According to Wood, the finished lamp had an inlet of 8.5mm.
Stephenson collected the lamp on 21st October 1815, and it was trialled at Killingworth Colliery the same evening. In his words, "I carried it with safety into a part of the mine where a strong blower of hydrogen [firedamp] was coming off. An experiment which was immediately repeated in the presence of two persons employed in that concern".
As he lifted the lamp to the mouth of the blower, all the gas inside the lamp ignited and the flame was extinguished. On relighting the lamp and holding it further from the gas stream, the flame increased then flickered and went out.
No trace of the first lamp survives, and the illustration of it in Stephenson’s treatise on his safety lamps (written in December 1816, published on 25th January 1817) shows a cylindrical 'tube and slide' lamp. It is thought to be a representation of the lamps he made in 1816, which had interchangeable tops with differing arrangements and sizes of holes.
Stephenson’s lamp, though safe to use around firedamp, was liable to go out unless carried with a very steady hand. He decided that the burnt air smothered the flame and so resolved to increase the air flow by having more tubes passing through the oil chamber. The lamp was despatched to David Matthews tinsmith of Middle Street, Newcastle, for modifications. The single inlet and slide cover were replaced by three narrow inlet tubes around and angled towards the flame, each 89mm long and of 1.15mm to 2.1mm internal diameter.
Presumably the first, conical, lamp was altered, though again Stephenson’s 1817 illustration shows a cylindrical lamp with an open top. As drawn, the circumference of the carrying case is pierced with a grid of small round holes and its lid is not perforated.
The improved lamp was tried on 4th November 1815, at the same location in Pit A, and "was found to burn considerably better". However, Stephenson decided further improvement could be made, noting "it did not entirely answer my expectations".
His new lamp had a ring of air holes around the base, a tube to let oil into the reservoir and a glass cylinder to enclose the flame. Initially he thought of surrounding the oil vessel with an increased number of much narrower capillary tubes for air intake, but as he’d already found that the firedamp burned at the exit of the tubes, he concluded that "the effect might be the same if I cut away the middle of the tubes".
He replaced the tubes with two plates, one below the air chamber around the oil reservoir and the other encircling the wick, perforated with holes from 1.2mm to 2.1mm diameter. The metal cap of the cylinder was similarly peppered with tiny holes. The grid of holes in the metal carrying case were made larger to let out more light.
On 20th November 1815, Stephenson discussed the details of his lamp with plumber and coppersmith Robert Watson of High Bridge, Newcastle, and Watson’s clerk Henry Smith. Watson manufactured and delivered the lamp a few days later.
Meanwhile, on 24th November, Stephenson demonstrated the modified second version of his lamp — with three capillary tubes &mash; to Charles John Brandling (1769-1826) and his brother Robert William Brandling (1775-1848), local land and colliery owners, and chemist John Murray (c.1786-1851) of Henderland.
The third lamp was tested in the Killingworth mine on 30th November, with many of the pit workers in attendance. Its success was such that several more were ordered from Watson to be used underground in dangerous areas. On 5th December 1815, it was exhibited at an evening meeting of the Newcastle Literary and Philosophical Society (‘Lit and Phil’ societies were local providers of scientific knowledge), where Stephenson and Wood gave a presentation that involved demonstrating the lamp’s efficacy using bladders of firedamp.
At the same time, a version of this latest lamp, with a 229mm tall glass chimney, narrowing at the top like a wine bottle, and a double row of air holes around the base, was "in the hands of the manufacturer".
Stephenson's perforated plate lamps were on sale in Watson’s shop from January 1816, with the design evolving over time. Perhaps Watson had tried to simplify production, for on 7th June 1816, Stephenson wrote to him, stressing that "When you make any of our lamps you must put caps upon the glass perforated with holes a little larger than the bottom holes. The caps must be done with hard solder. You must let none go away without the caps on the cylinder glasses".
By 1817, Stephenson had incorporated a wick trimmer — a wire hook alongside the wick tube that could be operated from the base of the lamp. It was similar to one developed by Davy for his lamp, the main feature of which was a wire gauze screen around the flame instead of a glass chimney and metal cover.
At a meeting held in the Newcastle Assembly Rooms on 1st November 1817, it was resolved that Stephenson was "entitled to a Public Reward" for discovering that firedamp would not explode through "Tubes and Apertures of small dimensions, and having been the first to apply that principle in the construction of a Safety Lamp". A subscription of £1,000 was raised, part of which was used to purchase and engrave a silver tankard. On 12th January 1818, at a dinner in the Assembly Rooms, Stephenson was presented with the tankard and the balance of the subscription.
Around 1818, the lamp was made smaller and shorter, with an openable lid that allowed heat to escape. The glass could be lowered from the top and the oil chamber in the base could be unscrewed to light the flame without the glass falling out. However, if the glass broke, the holes in the metal casing were too large to prevent firedamp from exploding. So, in about 1820, the pierced cover was replaced by wire gauze around and over the top of the glass (effectively making it a Davy Lamp).
Stephenson’s lamp — by now known as a 'Geordy' or 'Geordie' Lamp — was popular throughout the north east coal fields of England and was used widely in the mines of Northumberland and Durham. It gave more light than Davy's device and the glass chimney prevented the wire gauze from overheating. If too much firedamp entered Stephenson’s lamp it would explode inside the glass, extinguishing the flame and preventing the gas in the mine from igniting. Firedamp inside a Davy Lamp, though contained, caused the top of the gauze to become red hot and increased the chance of fire, sometimes with devastating consequences.
In the late 1830s, Watson's assistant Smith improved the lamp’s safety and reliability by ensuring the air intake passed through the base of the wire gauze and the air holes below the glass. Around 1844, Smith added an air chamber between the gauze and the air inlet holes.
Watson continued to be the principal manufacturer of Stephenson Lamps. Robert Watson was succeeded in the business in 1846, by his nephew Henry Watson. From November 1851, a domed top for the lamps was incorporated into the design, soon a standard feature.
Stephenson Lamps went out of use in the 1880s.
Tin plate (proptype): M.W. Hogg, Newcastle
Glass cylinder (prototype): Northumberland Glass Company, Lemington
Tin plate (second lamp): David Matthews, Newcastle
Copper plate (third lamp): Robert Watson, Newcastle
Research: ECPK
"Canny Stephenson & Davy - Commemorating the Bicentenary of the Miners Safety Lamp" by David Rimmer, Gary Chedgy, Christian Tauziede and Maurice Dawson, The Miners Lamp Society, October 2015
"Shedding Light in Dark Places: the story of the miner’s lamp" by Eric Edwards, published online, 3rd July 2013
"The Invention of the Miners’ Safety Lamp: A Reappraisal” by W.F. Watson, Transactions of the Newcomen Society, Vol.70, pp.135-141, London, 1998
"George and Robert Stephenson: The Railway Revolution" by L.T.C. Rolt, Penguin Books Ltd, London, 1984
"George Stephenson: The Engineer & His Letters" by W.O. Skeat, The Institution of Mechanical Engineers, London, 1973
"Report upon the claims of Mr. George Stephenson, relative to the invention of his safety lamp, by the committee appointed at a meeting holden in Newcastle, on the first of November, 1817", Baldwin, Cradock and Joy, London, 1817
"A description of the safety lamp, invented by George Stephenson, and now in use in Killingworth Colliery" by George Stephenson, 2nd edn, Baldwin, Cradock and Joy, London, 1817
reference sources   Smiles3ODNB

Stephenson Safety Lamp, site of