Patent slip

Invented by shipwright Thomas Morton in 1818,[1][2] 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 committee was sympathetic, in particular regarding the small return that Morton had seen during the initial patent period, but ultimately did not support the requested extension.

Originally, men or horses and block and tackle were used to provide mechanical advantage to drag the cradle and vessel up the slipway.

Other uses include repairs below the waterline, the replacement of propellers, inspections for insurance purposes, or the fitting of cathodic protection.

[4] In addition, a marine railway can substitute for a traditional waterway lock in areas where the terrain is poorly suited to an installation of that kind.

The Evans Bay Patent Slip operated in Wellington Harbour, New Zealand from 1873 until 1980, and is now a heritage area.