This is a very unusual design, and I have not found another example, even in the major collections. Inclining sundials usually have a fixed compass rose with rotating needle. This sundial has a floating card compass. In the usual form of floating card compass sundial the compass card is the sundial itself, complete with gnomon. This has the advantage of being self-orientating, automatically corrected for magnetic deviation for that time and place. The model here has the advantage that it is not restricted to a fixed latitude, but the sundial still has to be rotated to align with the compass. It has the disadvantage that you cannot easily compensate for magnetic variation over time and place, as in the conventional inclining dial.
Floating card dials became very fashionable in the 1820’s and 1830’s. My guess is that Watkins and Hill produced this model in response, but as a hybrid design it has no overall advantage to the established alternatives, and never became popular.
Condition: The sundial is in excellent condition, the brass retaining its original lacquer. The red Morocco covered case is worn, with losses to the leather, and one of the two catches is broken (see photos).
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Ganymede Antiques, established in 1992, is based in Muswell Hill, London, U.K. We specialise in scientific instruments from the 18th and early 19th centuries, with particular interest in sundials, and drawing and calculating instruments. We are always keen to buy interesting instruments, and entire collections. We exhibit at the twice yearly International Antique Scientific Instrument Fair in London. Keith Petts can be contacted at email@example.com