pay Pinkerton for his work. Interest was paid on the amount outstanding until the bill could be paid. The original plans for the canal section of the navigation included four locks, each of which was timber floored, and built to accommodate "Driffield-sized" Humber keels of . Keels could carry a maximum of 100 tons but were limited to a maximum of 70 tons in the Navigation due to draft limits. The initial locks were: Sheepwash Lock (now known as Town Lock) Whinhill Lock Wansford Lock Snakeholme Lock In 1776 the commissioners raised an additional £2,000, with which they hoped to construct a new lock at Thornham Bottoms, below Snakeholme, and to dredge the river below that. Instead they opted to convert Snakeholme lock into a two-lock staircase, which allowed vessels to use it over a greater range in water levels. Plans to extend their powers below Aike Beck, so that Hull Bridge at Tickton could be made larger were thwarted by Beverley Corporation in 1777, but some dredging of Frodingham Beck took place. The first recorded dredging between Emmotland and Aike Beck took place in 1783, and subsequently dredging was a prominent item in the accounts. The expected dividends of 5 per cent did not materialise, but dividends were paid in most years after 1774, starting at 1.5 per cent and rising to 4 per cent by 1790. By 1784, the navigation was making enough profit for the commissioners to build a warehouse and granary at Driffield. Development The 1790s were a period of prosperity for the navigation, as trade increased. In 1796 George Knowsley, a banker who was one of the mortgagees, proposed further improvements, but although William Chapman produced plans, they were considered too expensive. Two years later, the commissioners were working with William Wilberforce, their local Member of Parliament, to ensure that the proposals for the Beverley and Barmston Drainage Bill would not adversely affect them. In 1797, they considered again the problems posed by the small opening beneath Hull Bridge, and although Beverley Corporation initially said that they would never alter it, an agreement was reached after protracted negotiations, and in July 1801, an Act of Parliament was obtained to authorise its replacement. The new bridge was operational by April 1804, half the cost having been met by Richard Bethell, owner of the Leven Canal, on condition that the tolls for passing beneath the bridge were