Leonard Honey – “Sundials, ancient and modern”

This month’s talk was by Leonard Honey from Science Replicas based in North London. His interest in antique scientific instruments was reflected in a talk about sundials and their construction. Like many people, I thought that sundials were only found as static objects attached to walls or on plinths in the garden; this is clearly not the case, as apparently portable sundials were available after the twelfth century for use by the wealthy. Prior to that point the ancients used sticks to cast a shadow onto the ground or a hemispherical hollow carved in stone.

Leonard described the various types of portable sundial produced between the 16th to 18th Centuries (an activity known as dialling). Only when mechanical clocks became more reliable in the 19th Century did the use of sundials decline. We were shown some beautiful pictures of pillar dials which have a fixed pointer (gnomon) that casts a shadow down the outside of a tube marked with specific dates. Its use is limited to a particular location, so the introduction of the ring dial with a device to measure the sun’s height in the sky meant that the instrument could be used anywhere on the planet. The very attractive diptych dials were also described – these are folded into a small case like a closed book, with a small wire passing down across two faces acting as the gnomon. These portable sundials are very ornate, some in ivory cases, and covered in markings, including the names of European towns as reference points. Lastly we were shown pictures of a series of portable flat sundials with an enclosed compass.

Although these instruments are no longer in use, they have enormous aesthetic value as well as historical interest. Leonard and his wife brought along a display of replica dials and other astronomy related material which generated a lot of interest. These items can be purchased from Green Witch in Dry Drayton, or directly from Science Replicas.

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