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Calton Hill and Time

Following the creation of the Edinburgh Astronomical Institution in 1811 a small Transit House was constructed on Calton Hill. This is still in place today in the western edge of the enclosure. Unfortunately, due to damage over the years the roof had to be repaired and no longer contains the slit through which the light from stars would reach the transit telescope.

The window of this building contained the "Politician's Clock" - 2 faced. Mariners read one face at the window when setting their clocks, and the astronomer referenced the other face within the building. This clock is still within the observatory.

Coming all the way up the hill from the Port of Leith was not a popular activity, and in the early 1850's Charles Piazzi Smyth presided over the provision of a Time Ball on the nearby Nelson Monument. The ball would be raised at 5 minutes to 1, and dropped at precisely 1 o'clock. Its fall was controlled by an electrical pulse sent out from the observatory.

Whilst the provision of a Time Ball largely eliminated the need for mariners to climb the hill with their marine clocks, it was of no use in poor weather or in misty conditions.

Charles Piazzi Smyth therefore arranged for a gun to be fired at precisely 1 o'clock from the Edinburgh Castle ramparts. This started in 1861 and had its 150th anniversary celebrations in 2011. The gun was also fired by an electrical pulse sent on a wire strung between the Nelson Monument and the Castle - over 4,000ft long!

Both the 1 o'Clock Gun and the Time Ball are still operational today, a fine legacy of Charles Piazzi Smyth, the second Astronomer Royal for Scotland.