The first steamship to operate on the Mersey was the "Elizabeth", a wooden paddle steamer, which was introduced in 1815 to operate between Liverpool and Runcorn. There was considerable debate as to the best way of boarding a ferry vessel. For the steam ferry "Etna", which entered service at Tranmere on 17 April 1817, the idea of extension stages was mooted. These were long piers that were mounted on wheels and, by using a steam engine, could be wheeled in and out depending on the level of the tide.