There is evidence of coal mining in the Middle Ages in the shaft mounds, waggonways and similar archaeological features resulting from early mining activity in Middleton Woods. Before the 17th century the pits were bell pits and adits or day holes dug horizontally into the hill sides where the coal seam outcropped. In 1669 Frances Conyers of New Hall had "cole pits" in Middleton. The pits were small and numerous and many worked for a short time. Gin pits using horses to turn the windlass were the next development and the deeper pits had brick-lined shafts and wooden headgear for hauling tubs of coal and miners out of the workings. This type of mine was in operation when Anne Leigh married Ralph Brandling whose family owned collieries in Durham. Brandling's 1,200 acre Middleton estate supplied coal to Leeds but was disadvantaged in the trade by poor roads. Deep mining arrived with the advent of steam engines to pump water out of the mines and keep the workings dry making it possible to raise coal from greater depths. In 1780 a Newcomen engine was installed at Middleton and by 1808 the mine employed 90 hewers and 60 putters. The market for coal grew as Leeds and its industries expanded.