In 1700 watermen combined with their colleagues in cargo to form the Company of Watermen and Lightermen. The "free water clause", introduced by the West India Dock Act of 1799 and the gradual construction of a greater number of bridges, especially Westminster Bridge in 1750, forced great change on the river trade during this period of Industrial Revolution. Freight could now be moved along a river and canal system with waterway access to the Midlands and Bristol. The port provided London with its great wealth and relied heavily on the transshipping skills of watermen and lightermen to run smoothly. This was the boom time for lighterage and fortunes were made by the captains of the distinctive red sailed Thames sailing barges at this time.