How can a dolphin tell the time to the nearest minute?
Equinoctial dial for latitude 51° 28' North sits on a plinth made of Portland stone. A cresting wave is set on the plinth and supports the curved dial-plate, which forms part of a cylinder and is inclined so that it lies in the plane of the Equator. Two bronze dolphins hold the dial-plate in their mouths and curve over so that their tails almost meet above the dial-plate. The centre of the gap between the two tails acts as the gnomon.
The use of the different dial rims for Greenwich Mean Time and British Summer Time and of the two different hour-plates with the hour-lines marked as half of the analemma, means that the instrument is always accurate to the nearest minute. The rims are changed when the clocks change for daylight saving at the end of March and October while the hour-plates are changed at the solstices in June and December.
The sculpture was made by Edwin Russell and the object was cast at Brookbrae in London.