a small laboratory was built near the power house in mid-1896. trials were begun with several types of filter, but none were particularly effective, although they were better than land filtration. the old river bed soon became full of sludge, and the corporation purchased a boat, so that the sludge could be dumped at sea. the "joseph thompson" was built in barrow in furness at a cost of £24,837, and made its first voyage in december 1897. loading of the sludge took around 45 minutes, the journey down the ship canal took six and a half hours, and the sludge was discharged near the mersey bar light in five minutes.