binnacle

binnacle (formerly bittacle), the wooden housing of the mariner's magnetic compass and its correctors and lighting arrangements. The change from bittacle to binnacle came in about 1750, although the former name did not entirely disappear until the mid-19th century. The origin of the term would appear to be the Italian abitacola, little house or habitation, and it was used by the early Portuguese navigators to describe the compass housing. The French word for binnacle is still habittacle.

In addition to the compass and a light, the binnacle was the proper stowage for the traverse board, the reel with the log-lines and chip, and the 28-second glass used for measuring a ship's speed. Charts in actual use, if any, were also properly stowed in the binnacle. Later, when a ship's deviation was established and had to be corrected, it was where the Flinders bars and Kelvin spheres (see Thomson, William) were placed.