User:Yiba/sandbox/Artificial horizon

Artificial Horizon is an instrument to indicate where the horizon is, used mostly in a ship. It was born in the 16th century as a maritime navigation tool, when a visual observation was difficult in the night or in a fog, as a supplementary tool to sextant. With the advancement in navigational instruments, its use shifted in the 19 century to indicate a ship's attitude in relation to the horizontal plane for ensuring the precise elevation and deflection in naval gunnery up to World War II.

Roof Horizon
Mercury in a trough acted as the horizontal mirror to reflect the image of a celestial body to measure its elevation angle. These troughs were typically covered by a roof shaped glass cover.

Pendulum Horizon
In the 19th century, as an additional instrument to a sextant for finding the horizontal plane in ports and in the night. Manufacturers included John Lilley and Son, 9 London Street and Fenchurch Street, London (1870-85) and Whyte Thomson & Co., Glasgow