The river was also used to power the many textile mills that were built along the Derwent between Matlock Bath and Derby. Initially, the need for water power was quite modest, for example Lombe's Silk Mill in Derby, which is considered to be the forerunner of the later cotton mills, only needed to use the power provided by a small mill stream, and Richard Arkwright's Cromford Mill, the world's first water-powered cotton spinning mill, only used a small tributary of the Derwent in conjunction with a lead mine sough. The later mills at Belper, Darley Abbey and Masson Mill were much larger and needed to harness the full power of the river to drive their complex machinery. This required the construction of large weirs across the Derwent that still remain as significant features in the riverscape.