The Time Ball

on the Nelson Monument

and

One o'Clock Gun

at Edinburgh Castle

Time Ball on Calton Hill

In 1852, Edinburgh installed a time ball at the top of the Nelson Monument on Calton Hill, to enable the sailors in Leith Docks and the Firth of Forth to check and adjust their chronometers.

Time Ball in raised position

Photographed at 12.59pm -  2 October 2006

© peter.stubbs@edinphoto.org.uk

The Edinburgh time ball was devised by the photographer and Astronomer Royal for Scotland, Charles Piazzi Smyth, who had worked previously as assistant astronomer at the Cape of Good Hope Observatory, which had its own time ball.

The time ball mechanism was designed by the Edinburgh clockmaker, Frederick James Ritchie.

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Ritchie of Edinburgh still have the contract for maintaining the time ball and several of Edinburgh's public clocks, including the Floral Clock in Princes Street Gardens.

Observations of the stars were made, using the telescope on Calton Hill.  This enabled the precise time to be known.

On the Nelson Monument, the time ball was raised shortly before one o'clock every day, then lowered at one o'clock so that the people of Edinburgh and on the ships in the Firth of Forth could check their clocks and chronometers.

Mons Meg at Edinburgh Castle

This is not the canon that is used for the one o'clock gun!

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In 1861, a master clock on Calton Hill was linked by an overhead electric cable to a clock at Edinburgh Castle.  This enabled the one o'clock gun at the castle to be fired automatically at exactly one o'clock.

Equipment used for the observations at Calton Hill can still be seen in the Observatory on the hill.  The clock used to time the firing of the cannon at the castle is now on display in a case in the cafe at the castle beside the one o'clock gun.

The electric cable linking the castle and Calton Hill was 1,225 meters long.  It passed passed over Waverley Valley, without any support, at the height of 73 meters.

The gun could be heard from far afield.  The falling of the time ball at the top of the Nelson Monument could be seen immediately,  but it took several seconds for the sound of the gun to travel even the two miles from Edinburgh Castle to the ships in Leith Harbour.

Time-Gun maps were published in the Edinburgh & Leith Post Office Directories in 1861 and 1862.  These maps showed the time taken for the sound of the gunfire to travel across Edinburgh.

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