 The iron industry in the Weald, whose rich deposits had been exploited since prehistoric times, expanded and spread from its base in Sussex into Kent and Surrey after 1550.New furnace technology stimulated further growth in the early 17th century, but this hastened the extinction of the business as the mines were worked out.However, this period also saw the emergence of important new industries, centred on the valley of the Tillingbourne, south-east of Guildford, which often adapted watermills originally built for the now moribund cloth industry.