 The 1810s ushered in the era of modern lighting utilities. And as I wish you'll now hear, several lighting first occurred in 1816, the year without a summer, described in Byron's poem. Coincidence? Serendipity? Let's find out more with seeing the light. How the Victorians lit up Britain, written by Jeff Winkles. Among the earliest pieces of evidence that humans used artificial light to their advantage are these stone age lamps, which were probably used for cave paintings. The fuel is likely to have been animal fat, which solidified when the lamp was not in use. The intensity of the light could be varied by the number of wicks, which would have been plant based. Oil lamps in ancient Egypt commonly used castor, sesame or linseed oil as a fuel, with the wicks housed in the spout. Wicks were made with the pith of rushes, castor plant fibres, or even cloth. Notice that the top of the spout is above the top of the vessel. This meant that when the vessel was full of low viscosity oil, the oil under gravity would impregnate all of the wick. While ancient oil lamps had a reasonable luminosity, they lacked a certain degree of portability. There were also problems adjusting wicks, so candles started to be developed. Initially, they were simply bits of rush or other plant wicks coated in animal fat known as tallow. The first production line of candles in Britain was founded in London by the tallow Chandler's Company, which received its royal charter in the 15th century. Various forms of candles were subsequently developed, mainly using different types of animal fats. An example of a candle from sperm whale fat is featured in the bottom centre of the slide. Fast forward to the 18th century. You can see from these photographs how sophisticated oil lamps had become. Today we can switch on a light instantly to work, to read, to write, and replicate the intensity of daylight. In those days, the light was far less intense. We regularly see oil lamps in period dramas on film and television, but of course the lighting in these productions is enhanced by the artificial light required for filming. You can see in the bottom left picture that the 18th century lamps aren't too dissimilar from those of ancient Egypt. They've been enhanced with a glass cover that protected the flame while enabling air to circulate, but much of the underlying technology was the same. Viscosity of the oil was still important. The wick still had to be fed by gravity. In 1780, Amé Argonne, a pharmacist also known for improving the distillation of wine into brandy, invented an improved combustion oil burner, the Argonne lamp. You can see examples in the centre and write images. In those days, combustion was not a well-researched science. In fact, laboratory scientists were only just discovering the importance of oxygen in the process. The Argonne lamp has various air holes to enable the air to reach the flame, producing a more luminous flame that required much less frequent trimming of the wick. The use of gas for lighting was first recorded in Sichuan province in China in 500 BC. The gas came from fire wells, underground methane deposits. The gas was transported from these natural wells by bamboo pipes bonded together with a glue made from lime and tree seed oil. Pig's bladders were then filled with gas and pierced with pinholes which made an upward torch effect. It's been conjectured that the eternal flame inside the temple of Vesta, goddess of the hearth in Rome, was in fact a gas flame which emanated from methane wells beneath the soil. The Roman historian Plutarch records that the Vestal virgins who maintained this temple would ceremonially create a flame each year using mirrors focused on the sun. In support of this theory of a Vestal gas flame, you can see on the slide on the left that underground gas sources are often found quite close to the surface of the earth. The map to the right shows the location of gas wells in Europe. Down the spine of Italy there are several on land supplies and in Tuscany and Umbria natural gas does find its way to the surface but in very small quantities unfortunately well below the gas flammable limit. The development of the gas industry in the UK is credited to Scotsman William Murdoch. He developed a practical method of using gas for illumination while working for the Birmingham based Bolton and Watt, a company famed for producing some of the earliest steam engines. Murdoch illuminated his cottage in Red Ruth Cornwall with gas lighting having been sent there by Bolton and Watt to oversee the use of static locomotive steam pumps in the local tin mines. Others had experimented with gas as an energy source before. In the 17th century, the Reverend John Clayton had submitted a paper to Robert Boyle at the Royal Society explaining how he had distilled gas from coal and proposing its potential for lighting. But Robert Boyle died in 1699 and Clayton's observations lay forgotten in the archives of the Royal Society. Nowadays we think of gas energy primarily as a heating source but in the early years its use in lighting was far more important. We've seen earlier in this presentation the problems associated with oil lamps. Gas with its much brighter light presented several advantages particularly in industry where the working day could be extended to improve productivity. This chart shows the differences in luminosity of lighting sources from a standard candle on the left to an electric light on the right. A gas lamp was equivalent to 18 oil lamps. Industry saw the potential of gas lighting to extend the working day to provide safer working conditions by reducing fire risk and to reduce maintenance and building insurance costs. The emerging cotton industry was the first to capitalize on this potential with the Philips and Lee Cotton Mill in Salford Manchester probably being the first to be lit by gas. The gas would have been produced from a local generator before the development of anything like a gas mains pipe network. While industry led the way in gas lighting, its use in the street came later. The darkness of streets until the early 19th century offered a perfect opportunity for thieves, pickpockets and other criminals. This was a long-standing problem as early as 1417 the Lord Mayor of London ordained that lanterns be hung outside from Hallow Tide 31st of October to candle mass in early February. And in 1716 all householders whose house faced a street were required to hang out one or more lights to burn from 6pm to 11pm under the penalty of a one shilling fine for failure to do so. The first gas company to manufacture a public supply of gas was founded by Samuel Clegg who had been an apprentice of William Murdock at the Bolton and Watt Company. It was known as the Gas Light and Coke Company. Gas was generally produced from coal and coke as a byproduct was sold to domestic customers for heating purposes. There were also small gas generators that worked from other fuels, wood, oil and petroleum. An example in the Cambridge Museum of Technology is shown in the photo on the lower right of the slide. The first public gas works was built in Brick Lane in London in 1813. It supplied buildings rather than street lights in a small neighbourhood network. Preston is credited as the first urban area to realise the benefit of public street lighting in 1816 just in time to mitigate the gloom of the year without a summer. And at that time there were only 20 miles of gas mains in the UK. Whether it is by luck or design, the gloomy environmental conditions and increasingly smoke-filled industrial atmosphere of the late 1810s coincided with the swift growth of street lighting. By 1820, 15 towns had their own gas works and mains pipes and over the next decade many tens of thousands of street lights are installed. Most developed was the London Metropolitan Area which had 70,000 street lights by 1827. As we heard in the previous webinar, local historian Alan Brigham has charted the career of John Grafton, an apprentice of Samuel Clegg, who bought his coal gas technology to Cambridge in the 1820s. Grafton initiated the gas works site in East Cambridge that would become the Cambridge University and Town Gaslight Company. Gas was produced in furnaces known as retorts. This photograph shows the only remaining retort in the UK at Fakernum Gas Museum. Scotch cannell coal was used since its gas had better illuminated power than other coals. Cannell coals had been used in a neolithic period over 7,000 years ago as jewellery. Examples have been found in the Isles of Scotland. In the 19th century, David Graham of Middleton Gas Company published a treatise on the comparative commercial values of gas coals and cannells. Like John Grafton before him, Graham expanded his operations internationally. Grafton went on to develop lighting in Paris while Graham travelled to New Zealand to develop its gas industry. David Graham, incidentally, has another claim to fame. He is the great-great-grandfather-in-law of the son of Jeff Winkles, the author of this presentation. By 1872, gas lighting was widespread in cities like London. In that year, the French engraver Gustave Doré produced London, a pilgrimage, a book of engravings, seven of which show gas lighting. The two on the screen now show a gaslit railway station on the right and Billingsgate Market on the left. In the later 19th century, gas began to face competition as a utility from electricity. Much was made by the advocates of electricity about the inherent dangers of gas and the ease of use of electricity. The two illustrations shown here show publicity at the time. The argon design, originally for oil lamps, was adapted for gas lighting. You can see on the bottom right of the slide how the glass tube was incorporated to circulate the air around the flame. The glass tube protected the flame as well as people and objects and allowed thermally induced secondary air which would heighten the flame, increase its surface area and so produce more light. Early gas and oil burners obtained air for combustion from around the flame envelope. The Bunsen burner developed by Robert Bunsen premixed air and gas within the burner tube with the rest of the combustion taking place around the flame. This process was used for a long time before the gas mantle enabled even greater illumination. This is shown in the illustration on the right of the slide. The development of the Bunsen burner with its premixed system enabled the gas mantle to be developed. In the previous diffused design lamps suited up quickly reducing their brightness. Various materials were used for gas mantles to increase the blue wavelength of the flame and the overall illumination. These mantles were known as incandescent gas lights. As you can see from the photo on the bottom right, the lights supposedly gave a more powerful illumination than the electric bulb. Experiments with mantles in the 19th century led to the development of the incandescent gas burner which remained in use until the 1950s. This slide shows stages in that development. The picture to the left shows a gas lamp of an earlier design but incorporating the glass tube and induced air system. The mantle hangs down vertically. You can see that this light is considerably stronger than those illustrated on the right. It was discovered that temperature played an important role in the mantles incandescence. Wellsback, who worked with Robert Bunsen, used a mantle of rare earth metals lanthanum and zirconium. This was made possible by using a Bunsen type burner which generated temperatures of up to 1350 degrees Celsius. This breakthrough allowed for burners with shorter flames that still maintain high temperatures so lamps could be smaller and incorporate several mantles within one design for greater fuel efficiency as shown in the upper right picture. William Sugg was a lamp maker extraordinaire and went on to develop many gas appliances. This slide shows lamps of great artistic and aesthetic quality. You can easily imagine these designs hanging in large public halls and stately homes of the period. Sugg also patented a self-regulating flat flame burner. In his day supply pressures in local districts varied considerably. A self-regulating burner would not flare if there was a sudden change in gas pressure so the intensity of the light would remain steady. Sugg's burner, which gave it brilliant white light and operated relatively quietly, reducing the hiss caused by changes in pressure, proved successful in its day. The advantage of electricity over gas was the ease in which it could be switched on and off. Gas lamps required lighting at the valve. The picture on the bottom left shows a typical gas lamp with a mantle and glass cover and a gas valve operated by a chain and lit by a match or a taper. There were more inventive systems, which included gas pilots and control systems that could be wall-mounted. Later, these tried to mimic the same style of lighting as electricity, but since gas had to be transported to the light, there were more valves and tubing and domestic electricity ultimately eclipsed gas for home lighting. This slide shows the development of the gas streetlight. Improvements that increase the circulation of secondary air and increased luminosity can be seen in the design of mantle burners and luminous burners. A disadvantage of gas streetlighting was that the lamps had to be lit manually every night. Lamp lighters had a ladder and a torch known archaically as a lamp horn, originally made from an animal's horn. With tens of thousands of lights within a metropolitan area, gas companies employed large workforces. For example, in 1889, the South Metropolitan Gas Company of London had 21,000 streetlights, which would have required many hundreds of lamp lighters. Although there were attempts in the 19th century to automate the lighting of street lamps, it was only in the early 20th century that a reliable self-lighting system using a clockwork timer was developed by watchmaking company Horseman. You can see one in the middle of this slide. These timers are installed in the lamp to operate a valve as illustrated on the left. There are still several gas streetlights in working order in Cambridge. They've been preserved as historic monuments, for example, at Earl Street near Christ's pieces, Barrow Road of Trunkington Road and several on roads in Newnam. In the 19th century, most gas companies were independent and operated in a particular city or area where their works were located. There was an issue of standardisation. How should gaslight be measured? The Metropolitan Gas Act of 1860 defined a standard measurement, candle power. This definition lasted until the candela was adopted as the internationally recognised measurement in 1948. Metering was another issue for the gas industry to resolve. Charging a flat rate without being able to measure total consumption was unsatisfactory to customers. The first gas meter developed to overcome this issue was large in construction since it incorporated a water seal. An example of an elaborate Victorian meter case can be seen in the upper right of the slide. The dry gas meter was introduced in the UK in 1843 based on an ingenious American design that is still used today for most domestic gas meters. Gas meters were categorised by light capacity. A 10 light meter, for instance, would supply 10 gas lights, etc. A gas meter consists of a steel case with two compartments. In each compartment is a set of bellows which work slider valves that open or close ports to the bellows in the compartment. In this illustration, the yellow portion is full of gas. At the stage in the upper left diagram, the slider valve is allowing gas from the inlet into the bellows. In the upper right, gas from the inlet goes into the bellows. Under the pressure of the gas, the bellows are forced outwards which displaces gas from the outer chamber and out through the meter. The amount of gas displaced from the bellows and the amount of gas discharged from the outlet are the same. This is called a positive displacement meter. In the next stage, in the upper right illustration, the bellows are full of gas, but the slider valves have moved which, just like the first phase, pushes the gas in the outer case to the outlet. The third stage can be seen in the lower left because the bellows are full of gas. The inlet opens and permits gas into the outside chamber. This pressures the bellows, which then pushes out the gas in the outer chamber through the outlet. The fourth stage, shown in the lower right, repeats the process for the other chamber. Each bellows' worth of gas is counted on the meter index. One of the earliest applications of gas lighting was to the theatre industry. Outdoor theatres of antiquity had been lit naturally by daylight. From the Renaissance, candles were used in indoor theatres, first in Italy and then in England. Much later, argon oil lamps were used as the primary light source. Candle lit performances required hundreds of candles, as reconstructions have demonstrated, and you can imagine the fire risk. Theatre owners quickly saw the advantage of gas lighting, enhanced performances and more buns on seats. Once again, 1816, the year without a summer, coincided with the history of artificial lighting. In that year, Joseph Vickers, the manager of the East London Theatre, built a gas works on the premises to supply lighting to both the local streets and his auditorium. Once gas entered the theatre building, it went to a central distribution point called a gas table. From there, miles of rubber tubing carried the gas into outlets within the theatre. Public areas, such as auditoria, were the first to be lit by gas. You can see from the upper picture what a hazardous procedure it was to light the burners prior to a performance. The huge potential for stage lighting was quickly recognised. At this period, theatres were in much social meeting places, with stalls lit as brightly as the stage. Gas lighting gave much more prominence to the performance itself. Controlled by the centralised gas table, various portions of the stage could be lit up as and when required. Footlights at the front of the stage had reflectors. The lights would have emitted a lot of heat for the actors on stage. This slide shows footlights on the left and at the top, and wing lights on the right. Theatrical performances and exhibitions were enhanced by coloured lights. To produce this effect, rows of gas jets were covered with a wire guard over which transparent cloths of different colours were stretched. Sadler's Wells Theatre Archive has a prompt script from the mid-19th century that includes instructions for lighting each scene. As mentioned in the previous webinar, we also have records of illuminations in central Cambridge from 1863, when university and municipal buildings were lit up red and blue. All of this was not without risk, of course, and there was some public concern. At the top of this slide, you can see a cartoon that shows some of the risks involved. Although the first theatres to install gas, the theatre royal in Covent Garden burned down after stage lights which had not been properly extinguished set fire to the scenery. With so many gas lights, it was hard work to extinguish them all at the end of the performance. Covent Garden had its own gas generator which was extracted from oil rather than coal. Following an explosion, the theatre was closed for more than a year for repairs. You can see the Lord Chamberlain's notice to reopen the theatre on the bottom right. The invention of gas lighting and the Wells Back Mantle enables powerful white light to be produced, and this was developed into the spotlight. Thomas Drummond had seen a demonstration by Michael Faraday from which he developed lime light in which oxygen was mixed with hydrogen to heat a limestone block in Candescence, a reflector shaped the light into a narrow condensed beam, and this is where the phrase in the lime light originates. It was first used on Hearn Bay Pier in Kent in 1836 to illuminate a juggling performance. One of the most prestigious applications of gas lighting was inside Parliament. Once again, the ingenuity of Mr Sugg was tested with the task of lighting the House of Commons. Sugg reasoned that the rising air from the heat of the gas lights would create a ventilation system dragging in cooler air at the lower level. The rising hot air was exhausted by a chimney effect. This slide shows the ornamental burner system developed by Sugg. As the press reported, this enhanced the appearance of the oak ceiling as well as illuminating the speaker's floor. The light was emitted from the lower part of the lamp. Warm air in the proximity was drawn through this grill and out into an extractor system. The system stayed in place until the 20th century when it was finally replaced by electricity. Parliament Square was lit by a combination of high pressure lamps for street lighting and lower pressure lamps for precincts and perimeters of the Houses of Parliament. Illustrated here in a 1931 painting by William Monk. Another prestigious use of gas lighting was on Brunel's Great Eastern Steamship. Gas was used to light the public areas of the ship. The only existing record of this is the Drafton's drawing archived in the Royal Museums in Greenwich. Unfortunately, no record survives to how gas was either made or stored on the boat. One of the best known lighthouses in the UK, the Eddystone lighthouse in Cornwall, has gone through several incarnations. The second, designed by Rudyard in 1709, is shown in this painting in the upper right of the slide painted by a Dutch marine artist, Isaac Seilmacher. The third design was made by Smeaton in 1759. Through the 18th century, the lighthouse used 24 candles backed by concave mirrors. These were replaced by argon oil lamps in the early 19th century, which gave a greatly increased rating equivalent to 3126 candles. In 1841, a single oil lamp and prism lens system was introduced to concentrate a single source of light into a powerful beam. While there had been experiments to power lighthouse beams with gas from burning wood in France and the USA, in the UK, a competitive trial was conducted in 1873 at South Forland Dover. Three temporary lighthouses were built at the top of the cliff alongside the existing lighthouse. One was powered by oil, one by gas, probably from Maptha, a flammable liquid hydrocarbon mixture, and a third by electricity. The electric lighthouse won the trial. Ireland equipped nine of its coast of lighthouses with gas. John Wiggum developed lamps specifically for lighthouses, which used multiple pre-areated gas jets, as you can see in the diagram at the top of the slide. He built a gas works at Bally Head, first extracting gas from oil, then shale, and finally cannell coal. The system was replicated in other lighthouses in Ireland. Lighting was still a chief application of gas throughout the 19th century, but other uses were developed for the home, particularly when gas became more widely available and cheaper. You can see in the top right of this slide the Giza, named after nice, landic hot spring. These appliances were popular until the 1950s. In fact, the author of this presentation, Jeff Winkles, recalls having a Giza in his family's bathroom as a child. It was potentially very dangerous. A delayed ignition procedure meant that there was a small explosion in the Giza every time it was lit, and there was no flue to vent combustion gas. This design would not be permitted today. As well as lighting, William Sugg's company was influential in the development of other gas-powered appliances. into the 20th century. For example, here in the upper right are sanitary incinerators for workplaces, responding to the increasing number of female workers in the 20th century. Other innovations included gas-powered ironing apparatus, refrigerators still used in caravans today, usually LPG, liquid petroleum gas, a gas heated bath, and perhaps most strangely, a gas-powered radio. Now this wasn't just a novelty item. The radio worked by applying a gas flame to heat a thermocouple bimetal device, which generated a small electric current to power the radio receiver. Another ingenious early 20th century invention that used gas power was the Humphrey pump. Henry Humphrey designed a pump that involved a controlled gas explosion. The build-up of gas pressure caused the water to rise into a discharge pipe up to 35 feet above ground level. Installed worldwide, a relatively local example was built at Chingford in Essex at the King George reservoir in 1913. Four pumps, each lifted four million gallons of water per day from the River Lee into the reservoir. These pumps continued to operate until 1968 and they would have continued for longer if they'd been powered by natural gas. As we heard in the previous webinar, the gas industry also permeated art and aesthetics. The photo at the top is a found object sculpture, Venus du Gas by Pablo Picasso. The artist found this iron gas stove ring burner on a municipal tip and represented it as the Roman goddess of love rising out of the sea. It's been displayed at the Pompidou Centre in Paris and the Museum of Metropolitan Art in New York. The main competition to gas from the late 19th century was electricity. But during the Victorian period, electricity was relatively too expensive. A light bulb could cost a week's wages. The widespread adoption of electricity was also delayed for many years because each generator had a different output. Early electricity supply systems were direct current. DC created large voltage drops and limited the size of distribution networks which made electricity expensive. It was not until the 1890s that alternating current, AC, solved the problems of voltage and long distance transmission of electric power by using higher voltages and transformers. Metal filament lamps had been perfected in 1911 but different towns had different currents and manufacturers were reluctant to develop light fittings with no standard national market for their products. The breakthrough came when the Electricity Supply Act was passed in 1926, leading to the establishment of the National Grid. The growth of low cost electric current finally meant the end of gas lighting. Thank you for watching. If you've enjoyed this webinar, please remember that you can donate or volunteer through the Museum's website. And now a live question and answer session with Cambridge Museum of Technology volunteers. Robert, thank you very much. If you'd like to ask a question, please do submit it by any of the electronic channels listed on the slide. You can submit either via the webinar Q&A panel or by email address or through our Twitter or Facebook accounts. I'm Gordon Davis, a volunteer at Cambridge Museum of Technology. And I'd like to reintroduce the author of tonight's webinar, Jeff Winkles, a chartered engineer and member of the Institute of Gas Engineers and Managers. Jeff has, by his own admission, spent what seems like several lifetimes in the gas industry, so delighted to have a professional expert with us on today's webinar. Jeff began his career at British Gas and for the last 25 years has co-directed an international consultancy global energy associates that provides gas engineering support to organizations throughout the world. Welcome, Jeff. Okay, thanks, Gordon. And just as we get started on the Q&A, just a reminder that the webinar together with the Q&A will be posted on the Museum of Technology's website. You can revisit last month's webinar and Q&A on the page there. This is the webinar last month about the Cambridge University and town gas like company generated lots of interest. We've consolidated as many questions as we can answer, posted them on the webinar replay page and we're going to just talk about a selection of them now as we and then get into questions from today's webinar. I do have at the outset just one correction to make to my own webinar from last month. I'm happy to correct myself. The gas lamp that I featured in Little St Mary's Lane is in fact a fully functioning gas streetlight. I got confused by the electric spotlight that's positioned next to it. As Jeff has illustrated in his presentation, there are numerous other streets in Cambridge and the vicinity of the Museum of Technology that have working gas streetlights. Thanks to one of our volunteers, Kathy Gunn, for starting to map those out. So without further ado, we've just collated some of the questions from last month and Jeff has very kindly researched these questions. So Jeff, the first question, how did villages get their gas? I know this is a popular question from last month's webinar. Yes. Originally, of course, there was applied from Cambridge, but as the network grew, as gasworks became bigger and more efficient, only the larger gasworks were gas suppliers. So around Cambridge, Peter Byrne was probably the biggest gasworks that supplied gas. Other ones were in Hitchin, Norwich, Colchester, and they fed a national grid, which then fed into the villages. And I know there was a kind of follow-up question about the natural gas and how the, where the natural gas was now stored. Any additional comments on that? Yes. The gas holders that now you still see are historic monuments now. These were used for storing gas right up to the advent of natural gas. But since then, gas has been supplied at much higher pressures. The materials for pipe work have improved so that they can take higher pressures without leakage. So now gas is stored in the pipes themselves at very hard pressures like 80 bar. It's called line packing. Because as well, gas comes from the wells in the North Sea and that is supply as and when it's required. So it's no need any longer to have big storage containers like the gas holders. Well, thanks for explaining the disappearance of the gas holders. The next question was, I guess, a bit of a kind of a bit of mental arithmetic based on the gas holder that was featured in from the Cambridge University in town. Gaslight company that was constructed in the 1920s and that was a 3 million cubic feet gas holder. So it was a question really people would try and get an understanding of what the the input value was to output sufficient gas to fill that gas holder. It's a difficult question to answer, really, because there are different forms of gas, really, or different combinations of gas. Gas was produced as this seminar said on the previous one from directly from coal. That was a very low calorific value gas and left cocas of byproducts. Well, coke became used to create a water gas which was used to supplement the gas produced by coal. So it's very difficult to give an actual answer to how much coal was actually needed to fill to fill the gas holder because it really very much depended on the production process. There's an order of magnitude in terms of, I know, just as a sort of ballpark in terms of, yeah, was it thousands or tens of thousands? Do you have an estimate? Offhand, no, there isn't. I have got an estimate somewhere if I could find it. So we'll post it on the website. Don't worry. So there was a question about the byproducts. I know, again, we featured the byproducts both in last month's seminar and today. So a question of what was done with all the coke. Yeah, mainly coke, as I said, was sold as a domestic fuel initially. But a huge amount of coke was developed from the gas production. So it was always sold as domestic fuel, but part of it was used to produce this water gas, which is used to blend with other gases to create a sort of higher calorific value gas. The problem with the earlier gas production was it was a very low calorific value and very low heating value. And as more gas was required for heating, as I think from lighting, where in fact the heating value of the gas was important, there was a standardisation to try to give a standard gas throughout the country. And so the gas was enhanced by other means and part of which was used in coke as a blue water gas to blend. Okay, thank you for that explanation. And then just the final one from last month's webinar, just again relating generally but also to the Cambridge University and Town Gasworks site. How has the gasworks cleared of industrial pollution before site redevelopment? Well, there's a lot of pollution obviously from gas. That's why gasworks are on the outskirts of cities really because of the smell. In general, the worst pollutant really was iron oxides. Iron oxide was used to purify the gas and this left quite a nasty deposit which had to be got rid of really. There was a lot of spillage of this. It was buried in some cases in gasworks. The purifier beds were left where they were and often built over or covered over. That left a lot of pollution in the soil. I remember one of the old gasworks I worked on when it wasn't the gasworks anymore offices there. But where the purifier beds had been, you couldn't get weeds, weeds wouldn't ever grow there. It was quite a potent mix. What's interesting, I did some further research on the site of the University and Town Gasworks Company and the remediation. From the Environmental Report, from the Environmental Agency and the Planning Consent, it talks about excavation removal of up to nine metres depth of soil for the residential site. That's clearly visible to this day in terms of the artificial slope and drop that's been created between the retail sites on the upper and the residential sites on the lower. There was also a combination removal and containment by bentonites and absorbent clay. Along with the removal of the pipework, storage tanks and demolition to the base of the gas holders, there was then this backfilling of the excavated area with compacted material from a local quarry in Cambridgeshire, Mepple, back up to ground level. Then there is continuous groundwater monitoring and control well. I thought it was useful just to show the before and after as a reminder to the audience on the top of the photo, the pre-demolition from the 1990s and then demolition in the early thousands. And then some photos that I actually took earlier today, so that's a snapshot of the most current view. But you can see to Jeff's point, it is possible to greenify a Gasworks site. So one further comment is a lot of these sites tend to get redeveloped as either kind of sports retail or leisure. I'm sure sports aficionados could probably compile a whole list of sports stadiums that have been built over former Gasworks. Jeff, I don't know if there are any questions that you would like to take from the Q&A from today's webinar. No, I haven't seen any that we could answer now. Well, based on that we will, if you would like to ask a question, feel free to submit via email or through social media. We do look at all the questions and we respond to them as soon as we can get a response. I'd like to thank Jeff again for authoring his presentation and Robert Lloyd Parry, Aka Nunky Theatre for narration. Do look out for more information about forthcoming webinars and virtual museum events. Those will be posted through the museum's online channels. And with that producer may end the live broadcast.