Archimedes' screw pipe does not need to be perfectly watertight, as long as the amount of water being scooped with each turn is large compared to the amount of water leaking out of each section of the screw per turn. If water from one section leaks into the next lower one, it will be transferred upwards by the next segment of the screw. In some designs, the screw is fused to the casing and they both rotate together, instead of the screw turning within a stationary casing. The screw could be sealed to the casing with pitch resin or other adhesive, or
SS Archimedes fitted with Smith's patented propeller, "Princess Royal", was built in the north of England, and in 1842, several more screw-propelled vessels were built or launched in Britain, including "Bedlington", built at South Shields, "Bee", launched at Chatham, and the largest ship built to that date in Ireland, "Great Northern", launched at Derry. From this point, screw-propelled merchant ships grew rapidly in number. By the time the Cunard Line built the paddle steamer "Persia" for transatlantic service in 1856, the paddlewheel was already becoming an anachronism. Though Smith's "Archimedes" had played an important role in the introduction of screw propulsion, Smith