The patent slip or marine railway is an inclined plane extending from shoreline into water, featuring a cradle onto which a ship is first floated, and a mechanism to haul the ship, attached to the cradle, out of the water onto a slip. The marine railway was invented by a Scot, Thomas Morton, in the early 19th century, as a cheaper alternative to dry docks for marine vessel repairs, in particular below waterline. Larger modern marine railways can handle vessels of thousands of tons.(Wikipedia)