 De-watering workings at depth with 'rag and chain pumps', leather bags or 'kibbles' (metal buckets) were all ineffective.Deep lode mining was only made possible by two innovations, the first of which occurred in 1748, when John Williams of Scorrier House initiated the construction of the Great County Adit, a phenomenal feat of engineering, which drained mine workings through a system of adits.Over the next century this was extended from Poldice to include many other mines consisting of 63 miles (101 km) of tunnels in all.