but was built on a different scale, influenced by John Lombe's Old Silk Mill in Derby and Matthew Boulton's Soho Manufactory in Birmingham. Constructed as a five-storey masonry box; high, long and narrow, with ranges of windows along each side and large relatively unbroken internal spaces, it provided the basic architectural prototype that was followed by cotton mills and English industrial architecture through to the end of the 19th century. Arkwright recruited large, highly disciplined workforces for his mills, managed credit and supplies and cultivated mass consumer markets for his products. By 1782 his annual profits exceeded £40,000, and by 1784 he had opened 10 more mills. He licensed his technology to other entrepreneurs and in 1782 boasted that his machinery was being used by "numbers of adventurers residing in the different counties of Derby, Leicester, Nottingham, Worcester, Stafford, York, Hertford and Lancashire" and by 1788 there were 143 Arkwright-type mills nationwide. The early mills were of light construction, narrow – about wide – and low in height, with ceiling heights of only 6–8 ft. The mills were powered by water wheels and lit by daylight. Mills were made by millwrights, builders and iron founders. By the end of the 18th century there were about 900 cotton mills in Britain, of which approximately 300 were large Arkwright-type factories employing 300 to 400 workers, the rest, smaller mills using jennies or mules, were hand- or horse-driven and employed as few as 10 workers. Early steam mills Before 1780, only water power was available to drive large mills, but they were dependent on a constant flow of water and built in rural locations, causing problems of labour supply, transportation of materials and access to urban merchants for large mill-owners. Steam engines had been used to pump water since the invention of the atmospheric engine by Thomas Newcomen in 1712 and, starting with the engine installed at Arkwright's Haarlem Mill in Wirksworth, Derbyshire in 1780, were used to supplement the supply of water to the water wheels of cotton mills. In 1781 James Watt registered a patent for the first rotative steam engine designed to "give motion to the wheels of mills or other machines". Concerns remained over the smoothness of the power supplied by a steam engine to cotton mills, where the regularity of the yarn produced was dependent on the regularity of the power supply, and it was not until 1785