Since the One o'Clock Gun first became a part of daily life in 1861, maps have been produced to show the time taken for the sound of the famous cannon to travel from Edinburgh Castle to the outer reaches of the capital and beyond.
Cartographers would overlay a series of concentric circles over a standard map of Edinburgh, with each additional ring of distance from the castle representing the passage of one second.
For example: Leith, which was a separate burgh at the time, was marked as being between nine and ten rings away from the castle ramparts. This meant that residents near the port would hear the One o’Clock Gun a full 10 seconds later than someone standing in the middle of Princes Street.
Back in the 19th century, when the average person still relied on the sun to tell the time, knowing when the sound of the gun would reach you was genuinely something you could set your watch by.
And, with the invention of the combustion engine still a number of decades away, the sound really could be heard in practically every corner of the city.
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A particularly good example of a “Time-Gun” map is available on the National Library of Scotland (NLS) website. Published by W & A.K. Johnston in 1879, the fascinating plan used alternating red bands to make it easier to assess when each area would hear the familiar 1pm blast.
Alternative maps used a numbering system, allowing residents to be able to tell how many seconds it would take for the sound to travel at a glance.
161 years of tradition
While we no longer rely on the daily din to set our pocket watches, the tradition of the One o’Clock Gun has survived into the modern age.
The firing of the gun was the brainchild of businessman John Hewitt, who brought the idea to Edinburgh from Paris.
It is fired at precisely 1pm throughout the year, except for Sundays, Good Friday and Christmas Day.
The original gun was a 64-pounder. Since 2001, a 105mm field gun has instead been fired from the Mills Mount Battery.
The gun, which has been replaced a number of times since its inception, is also used several times each year to fire 21-gun salutes.
Designed to fire blanks, the One o'Clock Gun has reportedly witnessed action on one occasion, when it was used to deter German zeppelins during an air raid in April 1916.
This famous time signal is located on the north ramparts of Edinburgh Castle just outside the Redcoat Café. The 1pm firing continues to mess the breeks of tourists - and even many locals - to this day.
You can view a fully zoomable version of the 'Time-Gun' map of 1879 on the NLS website here.
