Heliochronometers are extremely precise forms of sundial
 capable of accuracy within one minute assuming it is in sunlight.

  Invented at the end of the 19th century with the introduction of
Greenwich Mean Time in Britain. 
Up until this time each major city in the UK had its own local time
 but with the expansion   of the railway network  a standardised time
 was necessitated.

The heliochronometer is calibrated  with months and days
to enable it to mathematically calculate the "Equation of Time"
compensating for the earths elliptical rather than circular
orbit of the sun which would otherwise result
in sundials being up to fifteen minutes fast or slow
depending on the time of year.

39" (99cms) Height to top of pedestal
10" (25cm) Height of Heliochronometer

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