binnacle

Binnacle with iron correcting spheres at each side and clinometer below compass

A binnacle is a case or box on the deck of a ship, generally mounted in front of the helmsman, in which navigational instruments are placed for easy and quick reference as well as to protect the delicate instruments. A binnacle may be subdivided into sections and its contents typically include one or more compasses and a oil lamp or other light source. Other devices such as a sand timer for estimating speed may have been stored in the binnacle as well.

The construction of many early binnacles used nails (mid 1700s), which were later discovered to cause magnetic deviations in compass readings. As the development of the compass and understanding of magnetism progressed greater attention was given to binnacle construction to avoid compass disturbances caused by iron.

With the introduction of iron-clad ships the magnetic deviation observed in compasses became more severe. Methods of compensation by arranging iron or magnetic objects near the binnacle were developed. In 1854 a new type of binnacle was patented by John Gray of Liverpool which directly incorporated adjustable correcting magnets on screws or rack and pinions. This was improved again when Lord Kelvin patented in the 1880s another system of compass and which incorporated two compensating magnets.

The ship's Binnacle List is the medical department's report of personnel at sick bay, excused from that day's duty.[1]

Etymology

Before 18th century bittacle, through Span. bitacula, from Lat. habitaculum, a little dwelling

References

Look up binnacle in Wiktionary, the free dictionary.

• This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.
• Alan Gurney, Compass: A Story of Exploration and Innovation, W.W. Norton & Company, 2004, ISBN 0-393-32713-2.