A Very Modern Idea – The Semaphore Network of the Convict System
Sending messages at a distance using visual signals is a phenomenon as old as human society, but in the early nineteenth century this reached a new level of sophistication just as it was about to be superseded by wireless telegraphy. At this time, too, sailing ships were reaching new levels of efficiency, just as they were about to be overtaken by steam. The flag signals of the (British) Royal Navy were changing to a mechanical system which allowed more complex messages to be sent. There were, of course, still limitations.
At the commencement of the Battle of Trafalgar in 1805, Nelson wanted to send the signal “England confides that every man will do his duty”, but the signaller pointed out that “confides” would need to be spelt out, whereas “expects” was in the code-book, and so the famous “England expects” signal was sent. Colonial Tasmania (a.k.a. Van Diemen’s Land) was very much part of the navy’s network, and the new system was quickly adopted in Hobart for land-based communication. At first this was from the signal station on Mt Nelson down to Battery Point in Hobart to announce vessels entering the Derwent, but with the arrival of the energetic (army) Captain Charles Booth to run the penal settlement at Port Arthur, the semaphore system of Southern Tasmania expanded enormously.
Booth developed a network of stations radiating out from Port Arthur - guard posts, farms, quarries and even mines. A means of communicating between them was needed, especially when a ‘bolter’ was ‘out’ – when a man had absconded. Under the guidance of Booth, nineteen semaphore stations on high points were developed to cover the whole of the Tasman Peninsula, and to send messages to and from Hobart. Where possible, a large tree would have its top removed to form the base of the signal mast, where not, masts very like those of a tall ship were constructed.
The mechanics of sending a message were quite cumbersome. Communication was established by running up a flag, and then messages sent by adjusting the angle of six arms on the mast. The various positions of the arms were capable of indicating any number between one and three thousand, and each number corresponded to a letter, word, phrase or even sentence recorded in a code-book. This code-book was the key to the system, and it must have been extremely well organised, because the system became very efficient. On a clear day, when only four intervening stations needed to be used, a message of twenty words could be sent from Port Arthur to Hobart and acknowledged in just fifteen minutes. When a convict had bolted, a message could get to the essential guard-post at Eaglehawk Neck in a few minutes.
To maintain this efficient network, however, a great deal of manpower was required. An archaeological survey of one semaphore station, above Wedge Bay, revealed a site of 200 metres by 50 metres walled round, with several buildings and possible animal pens. This was not a station occupied by just one or two men. As the convict system declined in the 1850s, these manpower requirements became unsupportable, and by 1857, communication by signal between Port Arthur and Hobart had been lost: it was not restored till the telegraph line from the capital reached the old convict site in 1900. By then, the once notorious Port Arthur had become a pleasant little village called Carnarvon.
Semaphore telegraph in Van Diemen’s Land, 1836-1880. Sketches by John Wadsley, 1984. Reproduced with permission of Port Arthur Historic Site Management Authority.