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Bob Peterson wrote-

>Ritchie was the first to develop the "wet-card" compass; previous to
>that all compasses were "dry-card" compass of the British type.

Permit me to quibble a bit, about that.

It's true that the US Navy adopted the Ritchie liquid compass as its
standard pattern as early as 1863, while the British Admiralty were to
retain the dry-card pattern as their standard for another 40 years.

However, Ritchie was in no way the first to develop the liquid compass. His
design was very similar to one patented by Crow in Britain in 1813. From
1845, the Admiralty had found it necessary to supply liquid
steering-compasses to certain ships for use in rough weather, in addition
to the standard pattern compass. In that same year trials had shown that
dry-card compasses were useless in ship's boats, and soon liquid compasses
became standard issue for that purpose.

A trial in 1847 compared six compasses, from different makers, on board a
steam mail packet. Three of those compasses were liquid-damped, and showed
their superiority, but that evidence was insufficient to shift the
Admiralty from their dry standard-pattern compass. But the fact that three
British makers had liquid compasses available, to supply and test, back in
1847, shows that Ritchie was developing on existing technology, rather than
innovating.

Ritchie had tried to interest the Admiralty in his design for the US Navy,
but true to form, the Admiralty did not respond.

My information comes from "Steady as she goes", a history of the Compass
Department of the Admiralty, by A E Fanning (HMSO, 1986).

George.


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