Ramsden.info -
Understanding Metrology
Ramsden.info -
Understanding Metrology
In the eighteenth century, before the invention and widespread use of reliable and accurate timekeeping pieces in the early nineteenth century, a time service was provided near ports and harbours intended to meet the needs of ship captains and navigators in determining their longitude whilst at sea.
According to the South African Astronomical Observatory S.A.A.O (http://www.saao.ac.za/assa/html/his-pl-obs_-_cape.html) Approximately in June 1823 Fallows shone an Argand lamp in the evening and doused it at a pre-arranged time.
According to the S.A.A.O (http://www.saao.ac.za/assa/html/his-pl-obs_-_cape.html) Early in 1833 Henderson started a new time service. He climbed onto the roof of the observatory and at an advertised time fired a pistol. (black charge only, no bullet in the barrel) The flash was bright enough for sailors to observe with a telescope from the harbour. When Maclear became director he improved on Henderson's pistol by firing a cannon from Signal Hill (a hill overlooking Table Bay) at the advertised time of 9 p.m. (21h00).
According to the S.A.A.O (http://www.saao.ac.za/assa/html/his-pl-obs_-_cape.html) The principle of the time ball is that a very large, visible (brightly painted) round object was hoisted up a pole. At an advertised time the ball was dropped and this was the signal for navigators and other interested persons to set their chronometers (watches) to the correct time.
This came about because a new Admiral, Patrick Campbell, was appointed to the Cape. His brother-in-law was Captain Robert Wauchope, the inventor of the time ball. English Astronomer James Pond took up Wauchope's idea and the first time ball in the world was erected at the Royal Greenwich Observatory in 1833. Campbell persuaded Maclear to follow suit but due to the reluctance of the Admiralty to spend money the time ball was erected at the Cape only in 1836.
By 1853 Cape Town has expanded so much that the ships in the harbour could not see the time ball on the Observatory grounds anymore. Two new time balls were added to the time service, one at Signal Hill and the other at Simon's Town. By 1861 telegraph lines were installed in the Cape Colony and the drop of the balls were now done electrically from the Observatory. Batteries had to be installed and were housed next to the Mertz building. In 1865 another time ball was added to the system, in Port Elizabeth, 500 miles (+/- 750 km) distant, in "a feat without parallel in the electric work."
According to the S.A.A.O (http://www.saao.ac.za/assa/html/his-obj-instr_-_time_related.html#clockHarrison) The Royal Cape Observatory received a new Harrison clock as one of its first instruments. (Circa 1827).