The rapid spread of the railway network in the nineteenth century led to “Greenwich” time being adopted in the UK by Act of Parliament in 1880. However, it was not until 1924 that the BBC was to start broadcasting a time signal. This led to a real need for a method of setting clocks accurately, for those who did not have ready access to the railway’s telegraph system.
This was solved by the invention of the heliochronometer by George James Gibbs. His application was submitted on 8th May 1906, and was accepted as Patent Number 10787 on 14th February 1907.
Gibbs did not have the necessary funds to set up business on his own, so went into partnership with William Renard Pilkington, and together they started to manufacture the Pilkington-Gibbs heliochronometer in Preston, Lancashire, UK. The heliochronometer was made until about 1914, when the outbreak of World War I stopped production.
Every chronometer was given a unique serial number, the highest known to me is serial number 953, indicating that no more than about 1000 were made. However, to date, I have only been able to discover the existence of about 50. I would be pleased to hear from anyone who knows the whereabouts of any others.
Mine has the serial number 932, so it’s quite a late one, probably made around 1912/3.
If you can’t find the serial number, it’s under the bottom edge - see here
The dial is quite difficult to install. There is a scale for latitude adjustment at the base, but the dial has to be dismantled to make the adjustment. Longitude correction is made to the time scale, and this can also incorporate daylight saving, but no scale indication was incorporated to assist. Originally, each dial was set up at the factory for the owner - there are usually two longitude scale marks on the time scale - one for Greenwich, and the other for the longitude of the home of the purchaser.
The dials cost about 10 guineas at the time (£10.50) - the equivalent of about £800 today, so they were an expensive item.
To use, the small inner date circle is turned to indicate today’s date. This action moves the upper vane left or right the correct amount to compensate for the equation of time.
Next, the larger outer disc is rotated until the sun shines through one of the pinholes on the upper vane, and the spot of light is centred in the vertical line on the lower vane. The time is then indicated on the time scale on the right hand side. It is accurate to about 1 minute.