Editing Newcomen atmospheric engine (section)

===Components===
Although based on simple principles, Newcomen's engine was rather complex and showed signs of incremental development, problems being [[empirical]]ly addressed as they arose. It consisted of a [[boiler]] '''A''', usually a haystack boiler, situated directly below the cylinder. This produced large quantities of very low pressure steam, no more than {{convert|1|-|2|psi|bar|2|abbr=on}} – the maximum allowable pressure for a boiler that in earlier versions was made of copper with a domed top of lead and later entirely assembled from small riveted iron plates. The action of the engine was transmitted through a rocking [[beam engine|"Great balanced Beam"]], the [[Lever|fulcrum]] '''E''' of which rested on the very solid end-gable wall of the purpose-built engine house with the pump side projecting outside of the building, the engine being located ''in-house''. The pump rods were slung by a chain from the arch-head '''F''' of the great beam. From the in-house arch-head '''D''' was suspended a piston '''P''' working in a [[cylinder (engine)|cylinder]] '''B''', the top end of which was open to the atmosphere above the [[piston]] and the bottom end closed, apart from the short admission pipe connecting the cylinder to the boiler; early cylinders were made of cast brass, but cast iron was soon found more effective and much cheaper to produce. The piston was surrounded by a seal in the form of a leather ring, but as the cylinder bore was finished by hand and not absolutely true, a layer of water had to be constantly maintained on top of the piston. Installed high up in the engine house was a water tank '''C''' (or ''header tank'') fed by a small in-house pump slung from a smaller arch-head. The header tank supplied cold water under pressure via a ''stand-pipe'' for condensing the steam in the cylinder with a small branch supplying the cylinder-sealing water; at each top stroke of the piston excess warm sealing water overflowed down two pipes, one to the in-house well and the other to feed the boiler by gravity.