Sadler, in 1798 which, as well as working the chain pumps, drove woodworking machinery and a pump to take water from a well round the dockyard for fire-fighting purposes. This well was some away and the pumps operated by a horizontal reciprocating wooden spear housed in a tunnel running from the engine house to the top of the well. The Sadler engine was a house-built table engine installed in a single-storey engine house with integral boiler; it replaced one of the horse-drives to the chain pumps. This engine was replaced in 1807 in the same house by another, more powerful, table engine made by Fenton, Murray and Wood of Leeds and, in turn, in 1830 by a Maudslay beam engine. In 1800 a Boulton and Watt beam engine was ordered as back-up and was housed in a three-storey engine house in line with the Sadler engine house. This engine was replaced in 1837 by another engine made by James Watt and Co. Space was very tight and expansion of manufacturing facilities was not possible, so by 1802 the drainage basin was filled with two tiers of brick vaults—the lower layer to act as the reservoir, the upper layer as storage, and the roof of the latter being level with the surrounding land, so creating more space. This allowed the construction of two parallel ranges of three-storey wood mills, the southern to incorporate both engine houses and their chimney stacks, the chain pumps and some wood working machinery. The northern range was directly over the vaults and was to house more woodworking machinery. The buildings were designed by Samuel Bunce, the architect of Bentham's staff. While the vaults were under construction Bentham was ordering woodworking machinery of his own design, mostly up-and-down saws and circular saws. These were fitted-up in both ranges, the power to drive them being transmitted from the engines to the north range by underdrives through the upper layer of vaults, and then by vertical shafts to the upper floors of the buildings. The final drives to the machines was by flat belts running on pulleys. This machinery was planned to cut timber for the numerous smaller parts used in shipbuilding, especially joinery, which had previously been cut by hand, such as components for tables and benches, as well as small turned goods like belaying pins. There is evidence that he had developed a rotary wood-planing machine but