The Gibraltar Time Ball.                    

In days of yore, navigators needing to pinpoint their exact position on the vast expanse of ocean could determine their latitude fairly easily but faced considerable difficulty in finding their longitude. To find their latitude they would measure the altitude of the sun (and occasionally other celestial bodies) at noon and compare that against a set of tables, The Nautical Almanac, accurately prepared by astronomers.

However, to discover their longitude they relied on time. They knew that the earth rotated 360’ in 24 hours; therefore that every hour that passed represented 15’ of rotation.  Since lines of longitude run pole to pole with an imaginary zero degree line (prime meridian) running through Greenwich, if you could find the time difference between noon at Greenwich and the local noon wherever you happened to be, then you would know the amount of rotation and hence the distance east or west of the Greenwich meridian. 

If for instance you know it is midnight at Greenwich but only 6pm where you are, then the world has gone a quarter way round, or conversely you have gone a quarter way round the world and therefore you are 90’ West of Greenwich (approaching the east coast of the Americas). That would be easy with a £5 digital watch but until the 18C, sufficiently accurate chronometers didn’t exist. What they had were rather expensive clocks that didn't work very well... and it cost lives.

One of the heroes of the capture of Gibraltar and other Mediterranean battles was a certain Admiral Sir Cloudesley Shovell. In 1707 he was returning to England with his squadron when they got lost in fog beyond the Scilly Isles. In true civil service fashion they held a meeting on board his flagship, the Association, to decide where, exactly, they might be. They decided, set off, and sailed smack into the Gilstone Reef (by the Bishops Rock Light) and were wrecked, losing 1700 lives; all for the want of a good clock.  Admiral Shovell himself, who was built like a brick outhouse, floated ashore where he was murdered by a local woman as he lay semi-conscious on the beach. She killed him for the large emerald ring on his finger. The point of this story is that the government of the day got so fed up with having to buy a new navy every few years, that in 1714 they set up the Board of Longitude, charged with the task of finding an accurate way of determining longitude at sea and offering a £20k prize for any invention that would give an accuracy of within 30 miles after the typical six weeks passage to the West Indies.

                 

                        Cloudesley Shovell and what he lacked; Harrison’s H4 marine timepiece.

The man who finally cracked it was John Harrison, a self taught carpenter and clockmaker from Yorkshire. He produced a number of progressively more accurate timepieces and eventually received his prize… nearly 50 years later in 1773. A copy of Harrisons’s H4, a watch weighing around a kilo, was used by Captain Cook. After a complete circumnavigation of the world it gave an error of just 8 miles. It took some time to produce chronometers in the large numbers that would allow them to be carried by all ocean-going vessels so the general transition to chronometers actually took until around 1830.

 To synchronize these watches at the beginning of a voyage, ships’ masters relied on land based signals. In some ports these were one o’clock guns, but unless the ship could see the gun’s smoke, the sound of the discharge would arrive later. Five seconds would elapse whilst the sound travelled 1 mile, so a ship at 5 miles distant would receive the time signal 25 seconds late. A better solution was required; enter the Timeball, stage left.

    

                                                            Timeball at the Royal Observatory Greenwich

Probably the most famous Time ball extant today is that of the Royal Observatory Greenwich, installed in 1833, but that was by no means the first. That honour belongs to Portsmouth, where Captain Robert Wauchope R.N. first tested the idea in 1829. Since the astronomical calculations for the exact time could only be made at observatories, he devised a scheme for those observatories to signal that information to ships. His Time ball was a huge metal sphere rigged on a pole equipped with a mechanism to drop it at an exact time each day; on the instant of the hour.  “It is raised half way up the mast at 12.55 am, fully to the top at 12.58 am and drops at 1pm precisely.” The efficacy of this system was universally applauded and by the time of his death, Wauchope’s Time balls were in use on every inhabited continent. By the turn of the century there were 360 Time balls in use around the world.

 

The Gibraltar Time ball station was set up at the Windmill Hill Signal Station in 1883. It was controlled by an electrical signal, sent from Greenwich, delivered by the Eastern Telegraph Company at 10am GMT each day. Mariners in the harbour had only to watch for the fall, to rate their chronometers. It had replaced an earlier device, a ball displayed from the yardarm of the station, where, should the ball fail to drop, perhaps in consequence of a telegraph failure then a black and white flag was flown from the mast.

Telegraph failures were not uncommon. The Victorian world-wide-web suffered occasional interference that was generally of little consequence. Damaged or incoherent signals could be re-sent; but that did not allow for ‘instantaneous’ time signals… when the moment had passed it was impossible to repeat it. There were quite lengthy periods when telegraphy was impossible due to telluric (ground) currents flowing from points in the earth of differing potential through the earth and the cable network.  Geomagnetic storms, thunderstorms and the aurora borealis could also produce such significant voltages that telegraphy became impossible. This instance for example, just 2 years after the introduction of telegraphy to the Rock:

“Telluric currents attained an extraordinary development during the aurora of 4^th February 1872, which we have mentioned as one of the most extensive known. It was seen in the west of Asia, the north of Africa, throughout Europe, and on the Atlantic as far as Florida and Greenland; at the same time an aurora was observed in part of the southern hemisphere. The disturbances in telegraphic communication were not less extensive, and were observed with great care, in great part of Europe. At the same time many of the submarine cables were so affected as to prevent the transmission of any messages; the disturbance was especially marked on the line from Lisbon to Gibraltar, on the Mediterranean cable, on the line from Suez to Aden, and from Aden to Bombay, and finally along the Transatlantic cable from Brest to Duxbury.”

 Later, on the 31^st October 1903, the telegraph system was disabled for several hours:

“The enormous development of the telegraph, telephone, cable and other applications of electricity since the date of the last great magnetic storm has caused the disturbance to be more generally observed than was previously perhaps the case. Practically the world’s whole telegraph system was upset, and information from this country, France and the United States and other lands shows that for several hours, communication was almost completely interrupted.”

By the early 1900s not only the management of the British Empire but nearly all international commerce relied on the telegraph, much as we rely on e-mails today.   It was very important to have a plan B for whenever the telegraph was unavailable.

So the Admiralty pursued two possible solutions; the magic of radio telegraphy, still in its infancy, and a more down to earth option, an accurate clock. The logic was undeniable, a highly specified clock, which could be  synchronized with Greenwich daily by telegraph, but would continue to remain accurate for three or four days when the telegraph was inoperable and it had to stand alone. The clock would operate the Time ball satisfactorily and could be corrected by an operator, if need be, when the telegraph signal was once again available.

      

The clock, termed an astronomical regulator, was commissioned from Victor Kullberg of London and installed in Gibraltar in 1904. It was essentially an 8 day, long case pendulum clock, the construction details of which may be found at 7361 National Maritime Museum. However, it is the correction of the clock that was so cleverly engineered. A pair of electro-magnetic coils embraced the pendulum but allowed it to swing freely and acted upon a U shaped permanent magnet attached to the pendulum rod and by passing a current through these coils an attractive or repulsive force would alter the natural period of the pendulum. So the clock could be brought to time without touching any part of the mechanism.

The 1908 List of Time Signals informs us; ‘that for the benefit of mariners the Gibraltar time ball is dropped at each hour of daylight, not just at 1.00pm.’ This clock was to prove entirely satisfactory for the next 30 years, by which time it was made redundant by radio time signals. A ship’s master could now rate his chronometer from the comfort of his own bridge with consummate ease.

 

Our time ball was decommissioned in 1934 and on the 15th October 1936 it was dismantled. During 1935 the clock was recovered to the Chart and Chronometer depot in Gibraltar and eventually, in 1983, shipped back to the MoD Chronometer Section, Herstmonceux, for cleaning and refinishing. It became an office adornment in the Hydrographic Office, Taunton before finally being transferred to the Royal Observatory Greenwich on 13th June 2002.

This is yet another little piece of our heritage that has disappeared overseas but, realistically, would it have fared so well had it remained on the Rock?

 

First published Jun 2021 at the History Society Chronicle.            Paul Hodkinson.