place, stoppings and traps. In this period, the normal means of creating the updraft needed was by using a furnace in the upcast pit. With a single shaft colliery this simple arrangement could not be followed, and so a timber brattice (B) was built from the top of the shaft to the bottom. Men and materials passed up and down on the downcast side, the pumps worked in the upcast. At Hartley a furnace was kept burning in the yard seam (E) with the rising hot gasses passing up the furnace drift (I) to join and draw foul air up the upcast side of the shaft. The vulnerability of such an arrangement had already been identified and publicised before the colliery was sunk. An explosion at the St Hilda pit in South Shields in 1839 had led (as the result of a public meeting) to the formation of a committee to consider the prevention of accidents in mines. The Shields Committee issued their report in 1843; it had found that mines in the North-East were unnecessarily at risk of explosions because they were generally inadequately ventilated with too few shafts for the size of the underground workings (a view supported by evidence from George Stephenson, amongst others). The committee's report had specifically argued against the practice for all new works (which it thought Parliament should legislate against), of sinking a single shaft and sub-dividing it by bratticing to separate in- and out-flowing ventilation air (since any explosion destroying the bratticing would destroy the ventilation of the mine and ensure the death by asphyxiation of those underground). It was later estimated that sinking two shafts instead of one would have cost an extra £900. In 1852, the pit was flooded to a depth of by water from the old pit. A powerful steam engine, 'the largest in the county employed in mining purpose', was therefore installed in 1855 to operate pumps to recover the pit. Pumping began in September 1855 (in June 1856 the pumping engine was shown off to a visiting French prince) but two years later the pit was not yet in full production and advertised for sale as 'just reopened'. The pumps were in three stages. The lowest stage lifted water from a sump connected to an adit below the low main seam up to the yard seam. There a second stage lifted the water up to a