A Mechanical Sundial
The dial was made by Jonathan or Jeremiah Sisson in the second quarter of the 18th century. The clock face was turned approximately south, the first pinhole was moved to the date and the orientation of the dial was altered until the spot of light from the first pinhole coincided with the second. Turning the dial turned the hands on the clock, which then showed the time.
Seen under glass in dark conditions in the Science Museum in South Kensington, London, this is an updated version of a much earlier post. Hand-held.
A Mechanical Sundial
The dial was made by Jonathan or Jeremiah Sisson in the second quarter of the 18th century. The clock face was turned approximately south, the first pinhole was moved to the date and the orientation of the dial was altered until the spot of light from the first pinhole coincided with the second. Turning the dial turned the hands on the clock, which then showed the time.
Seen under glass in dark conditions in the Science Museum in South Kensington, London, this is an updated version of a much earlier post. Hand-held.