text: Iron ore in the form of siderite, commonly known as iron stone or historically as mine, occurs in patches or bands in the Cretaceous clays of the Weald. Differing qualities of ore were extracted and mixed by experienced smelters to give the best results. Sites of opencast quarries survive from the pre-Roman and Roman eras, but medieval ore extraction was mainly done by digging a series of minepits about five metres in diameter and up to twelve metres deep with material being winched up in baskets suspended from a wooden tripod. This was less destructive of the land as spoil from one pit was used to backfill the previous pit allowing continued land use.
  The fuel for smelting was charcoal, which needed to be produced as close as possible to the smelting sites because it would crumble to dust if transported far by cart over rough tracks. Wood was also needed for pre-roasting the ore on open fires, a process which broke down the lumps or nodules and converted the carbonate into oxide. Large areas of woodland were available in the Weald and coppicing woodlands could provide a sustainable source of wood. Sustainable charcoal production for a post-medieval blast furnace required the timber production from a  radius of a furnace in a landscape that was a quarter to a third wooded. Forging and finishing of the iron from bloomeries and blast furnaces also required large quantities of charcoal and was usually carried out at a separate site.
  Water power became important with the introduction of blast furnaces and finery forges in the late medieval period. Blast furnaces needed to operate continuously for as long as possible and a series of ponds were often created in a valley to give a sustainable flow for the waterwheel. A campaign, as the production run was known, usually ran from October through to late spring when streams began to dry up, although Lamberhurst Furnace driven by the River Teise ran continuously for more than three years in the 1740s. Finery forges with three or four waterwheels to drive bellows and hammers needed more water than a furnace at times, although continuity was not as important. They tended to be sited downstream from a furnace if they were in the same valley. Ponds were created by building a dam known as a pond bay, which often served as a road, across one of the many valleys in the undulating Wealden landscape. In 1754 one furnace was so drought-stricken that its manager considered hiring workmen to turn the wheel as a treadmill. This need for continuous water power was an incentive in the development of the water-returning engine, a waterwheel driven by water raised by a steam engine pump.