The adoption of steam propulsion for warships led to large-scale changes in the Royal Dockyards, which had been built in the age of sail. The Navy's first 'steam factory' was built at Woolwich in 1839; but it soon became clear that the site was far too small to cope with this revolutionary change in ship building and maintenance. Therefore, in 1843, work began in Portsmouth on further reclamation of land to the north of the then Dockyard to create a new 7-acre basin (known today as No 2 Basin) with a sizeable factory alongside for manufacturing marine steam engines. The Steam Factory, on the western edge of the basin, housed a series of workshops: for construction and repair of boilers, for punching and shearing and for heavy turning; there was also an erecting shop for assembling the finished engines. The upper floor housed pattern shops, fitting shops and other light engineering workshops. Line shafts throughout were powered by an 80hp steam engine accommodated to the rear. New Brass and Iron Foundries were also built soon afterwards, on the southern edge of the basin, and in 1852 the Great Steam Smithery was opened alongside the Steam Factory (where Bentham's Metal Mills had formerly stood), containing a pair of steam hammers designed by James Nasmyth. Three new dry docks were constructed over the next 20 years, opening off the new basin, and another was built on reclaimed land west of the basin alongside the shipbuilding slips, which were now five in number (Slips 3-5 were covered by interlinking metal roofs, believed to have comprised the widest iron span in Britain when built in 1845). Meanwhile, facilities for building wooden hulls continued to be updated with a large sawmill having been built behind the slips in 1843.