Patent slip

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 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.

Invented by shipwright Thomas Morton in 1818, the marine railway offered an alternative to the expensive and time-consuming process of dry docking a ship to perform maintenance or repairs to its hull below waterline. The means and mechanisms over time became various, but always include a "cradle" onto which the ship is floated, and a mechanical mechanism for transferring the ship from water to land up an incline. The destination where work was performed was termed the slip.

Thomas Morton petitioned to extend the duration of his patent in 1832, before a Select Committee of the House of Commons. The committee, chaired by the Rt. Hon. Sir George Cockburn, was convened and heard the claim that the slow construction and implementation of such slips required the extension, that the cost of using such slip was one tenth that of using a dry dock, and that by hauling completely onto a clear area it was easier to carry out maintenance. The committee was sympathetic, in a particular regarding the small return that Morton had seen during the initial patent period, but ultimately did not support the requested extension.

The process of slipping a vessel is an inexpensive and straightforward way to take a large vessel out of water for inspection or repair. In tidal harbors and ports, it is normally necessary to wait for high tide. In many cases, it is possible to take the vessel out of the water on one tide, and to make repairs and return it to the water on the next tide.

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