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One o'Clock Gun


Gun Exhibition

Installing the Cable

Professor Charles Piazzi Smyth, the second Astronomer Royal for Scotland, supervised the project to set up the One o’clock Gun on the Half Moon Battery at Edinburgh Castle in 1861. The time gun fired for the first time on 7th June that year, having failed to fire on the 5th and 6th.

The time gun fired automatically when an electrcal impulse was sent from the observatory’s master clock to the time gun’s clock via a cable hanging over the city. Frederick James Ritchie the proprietor of James Ritchie & Son who designed the time gun's clock, hired a crew of sailors from Leith to rig the cable which was over 4,000 feet long between the Castle and the Nelson Monument.

It could be heard clearly at the Port of Leith and was invaluable at times that the weather obscured the Time Ball on Calton Hill.

With the move of the Royal Observatory on Calton Hill to Blackford Hill the automatic firing was initiated from this new observatory. This was done for the first time on the 8th of October 1895.

The Gun is still in operation today but it is now fired directly at Edinburgh Castle using up to date timing.


1 o'clock gun - Historical Image

Reproduced by permission of the Royal Society of Edinburgh, from the RSE’s Piazzi Smyth Bequest, held on deposit at the Royal Observatory Edinburgh.

A 24 pounder mounted on a wooden carriage was chosen to fire the daily time signal in June 1861. The gun failed to fire and was replaced by a 12 pounder which was replaced a few months later by an 18 pounder.


1 o'clock gun - Historical Image

A 32 pounder breach loading cannon on a sliding ‘dwarf’ carriage was introduced before the First World War to fire the daily time signal.


1 o'clock gun - Historical Image

An 18 pounder field gun replaced the 32 pounder in June 1923. A pulley system was fitted to the firing handle by James Ritchie & Son connecting the lanyard to the weight in the clock


1 o'clock gun - Historical Image

The time gun was moved to the Mills Mount Battery after an unexplained explosion damaged the Half Moon Battery in August 1971.


1 o'clock gun - Historical Image

The 25 pounder was replaced by a 105mm Light Gun in November 2001