sentences:  The Roman settlement seems to have been abandoned by the 4th century, and there is no evidence of Saxon settlement.By the Middle Ages Bristol had become a major port, with all traffic between the port and the sea having to pass through the Avon Gorge and past Sea Mills.In 1712, Joshua Franklin, a Bristol merchant, built a wet dock at Sea Mills, to eliminate the need for large sailing ships to navigate the dangerous River Avon any further upstream.