A diptych dial is a type of sundial with two hinged leaves which open like a book to use shadows cast by the sun to tell the time.

When opened, a cord holding the top leaf of the dial in its upright position acts as the gnomon. The dial is put on a horizontal surface and orientated so that the gnomon is pointing towards true north. This is done with the help of a compass embedded in the horizontal leaf within the main dial. As the Sun moves round, the shadow moves across the dial marking the passage of the day. Times in places of significance can also be calculated from the dial’s readings. MHS.OU

These beautiful pieces were intricate and costly, often made using ivory. The dial shown here is my own. I’d love to be able to say that it is a rather rustic version of a valuable diptych dial, but it is in fact a cheap knock-off from eBay that I bought to test the workings… or is it the real deal?

There are many museums with watch and clock collections – for example (in the south) Oxford (Museum of the History of Science), London (V&A, Science Museum), and Greenwich (Maritime Museum).

3 PRECIOUS IVORY DIPTYCH DIALS

 

CHEAP & CHEERFUL BUT QUITE FUN

GSS Category: Diptych Dial; Diptych Sundial; Unusual Sundial

All photos Keith Salvesen; Museum of the History of Science, Oxford University