Description: At the peak of gas production, the industry nationwide employed one percent of the total workforce, and served eleven million customers. Every town had a gas works and gasometers became a familiar site, using coal to produce a (toxic!) gas which was a combination of hydrogen, carbon-monoxide, methane, carbon di-oxide and nitrogen. Early gas retorts were horizontal tubes about 12 inch in diameter which were charged (filled with coal) and, having given off the gas, discharged (the coke removed) by hand through an iron door at one end called the mouthpiece to be stored in the gasometers. It was slow, dirty back breaking work. As the demand for gas grew in the factories and the home for heating, lighting and cooking and streets were also lit by gas lighting, so the efficiency of the methods of making it improved. Automatic stoking machines were first used in 1868 and gravity fed, inclined retorts were developed in 1885. After a century and a half of using coal, attention began to be focused on using, first oil, as the raw material for gas production, then natural gas. Natural gas offered an important benefit over town gas; it was 'clean' and burned without giving rise to so much pollution from smoke, soot, dust, grit and sulphur dioxide. It enabled gas users to comply with the Clean Air Act 1956. Another important advantage is that it is non-toxic because it doesn't contain carbon monoxide which in the past had been responsible for a number of deaths. In 1959 the world's largest natural gas field, some 300 miles square, was discovered in Holland. Exploration began in the North Sea and six years later in 1965, natural gas was discovered in the West Sole area of the North Sea, 40 miles offshore. This was followed a year later by the discovery of the largest North Sea field, Lehman Bank. Other gas fields followed and soon there was enough gas to supply the whole of Britain for many years. Within 18 months of the first finds natural gas was supplying 10% of Britain's needs. Within 5 years over half of those needs were supplied. Natural gas has different characteristics to town gas and this meant that all gas appliances had to be converted to use the new fuel. This led to the eventual decline of producing gas from coal, and most gas works were no longer needed. The gas holders seen here were demolished in 1965.