Article of the month December

Clock and Sundial

Below is an antique clock by David Buschmann.
The clock dates from the second half of the 17th century.

The clockface is made equal to a south-facing vertical sundial with hours from VI to VI.

There is only one hand, running ‘anticlockwise’ and indicating on the sundial face the time during 12 hours.
Then, the hand resets and indicates the next 12 hours.

A special construction in the clock ensures that the movement of the hand takes into account the decreasing and increasing distances between the hour lines.

A pole style, centred on the hand’s centre of rotation, permitted the clock also to be used as a sundial.
This combination enabled one to regulate the clock to local apparent time, which was the custom at the time.

The clock is also provided with date curves in accordance with the signs of the Zodiac.
This allows one to read the date using the shadow of the end point of the pole style, or of an additional index on the pole style.