Geograph - photograph every grid square

Made by Gunning Sundials.
A Heliochronometer is the acme of sundials. It is only the heliochronometer that gives a direct and accurate reading of Standard Time throughout the sunlit year. To a greater or lesser extent, all other sundials fall short of this capability. Most will only reflect accurate time on four days of the year. By comparison, the Heliochronometer is ‘right’ every day and stands a fair chance of being more accurate than your watch. Clocks and watches, by their very nature, can only keep time whilst sundials determine it. And the unique capability of the Heliochronometer is that it determines it precisely to the minute.
A hundred years ago, heliochronometers were being used to set the times of civic clocks, to run the railways and to control several other time sensitive operations. Sadly the introduction in 1913, of the radio time signal spelt the death knoll to this successful commercial enterprise.
(From Gunning website)