tolls on the witham had gradually risen as improvements had been made. £263 was raised in 1763-4, and had reached £898 by 1790. in 1819, income exceeded £4,100 for the six months from march to september, and a five per cent dividend was paid in the following year. by 1826, over £180,000 had been spent on improvements, and another £40,000 was needed. however, the proprietors were still optimistic, and commissioned sir john rennie to investigate an extension to link the witham to the river ancholme, but although he made two proposals, neither was implemented. most traffic was carried by sailing vessels in barges hauled by horses, but in march 1816, the first steam packet boat arrived on the river. it was named "witham" and had been built by shuttleworth and robinson, whose yard was on sincil dyke. despite a boiler explosion in march 1817, fortunately without causing injury to any of the crew or the 30 passengers, a second steam packet was operating by july 1817, and they soon displaced the sailing packet boats. during a flood in 1828, one of them lost power when a floating hedge became jammed in the paddle wheels. in the following year, a lincoln man, william pool invented a new type of paddlewheel, which resulted in the boats travelling faster, and in 1836, wooden vessels were superseded by iron packet boats.