Canal inclined plane

An inclined plane is a type of cable railway used on some canals for raising boats between different water levels. Boats may be conveyed afloat, in caissons, or may be carried in cradles or slings. 
An inclined plane is quicker and wastes less water than a flight of canal locks, but is more costly to install and operate. A development of the idea is the water slope. An alternative to consecutive locks is a boat lift.
Operation.
Typically, such a feature consists of a slope, with one or more rail tracks on it. Boats are raised between different levels by sailing into water-filled tanks, or caissons, with wheels on the bottom and watertight doors at each end. The caisson is mounted on an angled wheelbase, to keep it horizontal to the water level, and is generally aligned sideways to the slope. These are drawn up or down hill on the rails, usually by means of cables pulled by a stationary engine. In most designs two caissons are used, one going up and one down, acting as counterweights for greater efficiency. When the caisson has reached the top or bottom of the slope, the doors open and the boat leaves.
There are also inclined planes without a tank or caisson, instead carrying vessels up out of the water cradled in slings or resting on their keels. In a few cases the boats were permanently fitted with wheels.
History.
Inclined planes have evolved over the centuries. Some of the first were used by the Egyptians to bypass waterfalls on the Nile. These consisted of wooden slides covered with silt which reduced friction.