Technological change affected not only ships' means of propulsion, but the materials from which they were built. By 1860 wooden warships, vulnerable as they were to modern armaments, had been rendered largely obsolescent. The changeover to metal hulls not only required new building techniques, but also heralded a dramatic and ongoing increase in the potential size of new vessels. The Dockyards found themselves having to expand in kind. At Portsmouth, plans were drawn up in the late 1850s for further land reclamation north and east of the new Steam Basin, and from 1867 work was begun on a complex of three new interconnected basins, each of 14–22 acres. Each basin served a different purpose: ships would proceed from the repairing basin, to the rigging basin, to the fitting-out basin, and exit from there into a new tidal basin, ready to take on fuel alongside the sizeable coaling wharf there. Three dry docks were also constructed as part of the plan, as well as parallel pair of sizeable locks for entry into the basin complex; the contemporary pumping station which stands nearby not only served to drain these docks and locks, but also delivered compressed air to power cranes, caissons and capstans. This "Great Extension" of Portsmouth Dockyard was largely completed by 1881.