A gas holder or gasholder, also known as a gasometer, is a large container in which natural gas or town gas is stored near atmospheric pressure at ambient temperatures. The volume of the container follows the quantity of stored gas, with pressure coming from the weight of a movable cap. Typical volumes for large gas holders are about , with diameter structures. Gas holders now tend to be used for balancing purposes to ensure that gas pipes can be operated within a safe range of pressures, rather than for actually storing gas for later use. Etymology Antoine Lavoisier devised the first gas holder, which he called a gazomètre, to assist his work in pneumatic chemistry. It enabled him to weigh the gas in a pneumatic trough with the precision he required. He published his Traité Élémentaire de Chimie in 1789. James Watt Junior collaborated with Thomas Beddoes in constructing the pneumatic apparatus, a shortlived piece of medical equipment that incorporated a gazomètre. Watt then adapted the gazomètre for coal gas storage. The anglicisation "gasometer" was adopted by William Murdoch, the inventor of gas lighting, in 1782, as the name for his gas holders. Murdoch's associates objected that his "gasometer" was not a meter but a container, but the name was retained and came into general use. Gas holders were marked as gasometers on the large-scale maps issued by the British Ordnance Survey and term came to be used to label gas works, even though there may be several gas holders at any one gas works. However, the term "gasometer" is still discouraged for use in technical circles, where "gas holder" is preferred. The spelling "gas holder" is used by the BBC, among other institutions, but the variant "gasholder" is more commonly used. History Before the mid-20th century coal gas was produced in retorts by heating coal in the absence of air, the process being known as coal gasification. Coal gas was first used for municipal lighting, the gas being passed through wooden or metal pipes from the retort to the lantern. The first public piped gas supply was to thirteen gas lamps installed along the length of Pall Mall, London, in 1807. The credit for this installation goes to the German inventor and entrepreneur Frederick Albert Winsor. Digging up streets to lay pipes required easements, and this delayed both further installation of street lighting, and the installation of gas for