Sir William Thompson's Dry Card Compass.

In 1880, Sir William Thompson was commissioned by the Astronomer Royal to produce a mariners compass with the qualities necessary for thoroughly satisfactory working in all weathers, in all seas and in every class of ship.

Yet is has small enough needles for the perfect applications of the Astronomer Royal's method of counteracting of the quadrantal error for iron ships (the compass error induced by an iron ship's own magnetic field). He produced his renowned Dry Card Compass, a superb example of which you will find on the front bar counter.

Beneath the hand-made compass card, there are eight small magnetic needles made of thin steel wire suspended on silk threads fixed to the outer rim of the card.