Located on Calton Hill in Edinburgh, this tower forms a monument to Admiral Horatio Nelson, the British Navy Commander at the Battle of Trafalgar. Completed in 1807, the monument was topped by a Time Ball in 1854 by the Astronomer Royal, Charles Piazzi Smyth (1819 - 1900), which falls down its mast daily (except Sunday) at 1.00pm. This acted as a time signal for the ships berthed off the Port of Leith, saving them having to walk up to the Observatory in Calton Hill to set their chronometers.
In 1861 the famous One O'clock Gun at Edinburgh Castle began it signal, also instigated by Smyth. It was fired by means of electrical signals along a single span of wire between Calton Hill and Castle Hill.
A plaque above the entrance to the Nelson monument reads as follows:
To the memory of Vice-Admiral Horatio Lord Viscount Nelson, and of the great victory of Trafalgar, too dearly purchased with his blood, the grateful citizens of Edinburgh have erected this monument: not to express their unavailing sorrow for his death; nor yet to celebrate this matchless glories of his life; but, by his noble example, to teach their sons to emulate what they admire, and, like him, when duty requires it, to die for their country.
The plaque is topped by a model of the Spanish ship San Josef, captured by Nelson at the Battle of Cape St. Vincent (1797), which he commanded when it was fitted out for Royal Naval service in 1801 and which became part of his heraldic arms.