EQUATION OF TIME - JOHN TOPPING C.1720
The clock pictured here by John Topping is an extremely rare example of the 'Equation of Time' calculation on an early 18th century Longcase Clock. It is pictured here purely for research within Wikipedia and not for sale or any other commercial purposes. People can ask me questions relating to the 'Equation of Time' but the clock is not for sale.
We are all aware of the passage of time, yet we can not see it. Many inventors have tried to measure time but it was not until the invention of the pendulum that considerable increased the accuracy of clocks that the calculation of the 'Equation of Time' became very relevant to clocks.Before the advent of the long pendulum in the early days the clocks were very inaccurate and so calculating the difference between 'solar' and 'our time' would have been of little consequence.The long pendulum was first invented by Christian Huygens, a Dutch scientists in 1656.The oscillations of the pendulum reduced error to less than 1 minute per day and eventually to less than 10 seconds per day.Peter Clare, a clockmaker in the 18th century, who worked in Manchester insisted his clocks were right and the Sun was wrong. A memorial to him reads.
Here's the cottage of Peter, that cunning old fox, Who kept the sun right by the time of his clocks.
Many people might think Mr Clares observations foolhardy, but it would be folly to dismiss them.
The clock pictured here by a maker called John Topping of London. It is a superb month duration, walnut Longcase clock with a dial showing the Equation of Time.With these increasingly more accurate clocks, the difference called the 'Equation of Time' became more relevant, and Mr Clare was right to some degree his clocks were more accurate than the sun.
The Equation of Time refers to the difference between the suns time and that shown by the clock, this varies by up to 16 minutes per day during the year. Only on four days in the year is there no difference between the suns time and the time shown by clocks. The days on which the clock and the sun should usually agree are the 15th of April, 15th of june, 31st of August, and the 24th of December.
Effectively Peters Clares clocks were more accurate than the sun, this is a result of the elliptical rotation of our planet.
The clock by Topping shown below is one of the few clocks ever made showing this calculation on a year calendar. It lets the operator know just how many minutes less or more the clocks time is from the suns time, effectively making it easy to set your clock in the 18th century by means of a sun dial.
This clock also has the special feature of a spherical moon, showing the true shape of the moon, this is accompanied with a tidal times indicator and rise and fall of the pendulum, making for changes of seconds to the timekeeping. It is housed in a superb elegant burr walnut cabinet.
Very few clockmakers ever had the talent to make such complex clocks and only the finest clockmakers have examples to their work. These are very few and far between. Tompion I believe made 3 equation clocks,Topping as listed here made a few, Williamson, who made several equation clocks for Quarre and the maker Gregg.Clearly very few are still surviving today. The complexity of the movement is mind blowing.