promotes the use of palisade fencing over opaque, usually brick, walls as criminals cannot hide as easily behind the fence. The City of Johannesburg manual on safety describes best practices and maintenance of palisade fencing, such as not growing vegetation in front of palisades as this allows criminals to make an unseen breach. Virtual electric fence In a virtual electric fence system each animal has a collar with a GPS unit which is set to produce first an audible warning and then a shock as the animal approaches a programmable boundary. Pet fences to control domestic dogs have been used since 1973, and the first system for livestock control was developed by Peck's Invisible Fence Co, now Invisible Fence Inc., in 1987. An early application involved goats and Euphorbia esula. Virtual fencing has been used by the Royal Society for the Protection of Birds in England to control grazing in wild and sensitive landscapes without the need for expensive and visually intrusive fencing. Companies which have developed this technology include the Norwegian Nofence, the Australian Agersens (brand name eShepherd) and the American Vence. History First published in 1832, Chapter 7 of Domestic Manners of the Americans by Fanny Trollope describes an arrangement of wires connected with an electrical machine used to protect a display called "Dorfeuille's Hell" in the Western Museum of natural history in Cincinnati, which she herself invented. Published in 1870, Chapter 22 of Jules Verne's 20,000 Leagues Under the Sea, describes "The Lightning Bolts of Captain Nemo"the use of electrification of a structure as a defensive weapon. Published in 1889, Mark Twain's novel A Connecticut Yankee in King Arthur's Court, uses an electric fence for defensive purposes. David H. Wilson obtained United States Patent 343,939 in 1886, combining protection, an alarm bell, and telephone communications. He constructed an experimental 30-mile electric fence energized by a water wheel in Texas in 1888, which proved successful at keeping cattle separated, but was deemed impractical as a business venture. In 1905, the Russian army improvised electric fences during the Russo-Japanese War at Port Arthur. In 1915, during World War I, the German army installed the "Wire of Death", an electrified fences along the border between Belgium and the Netherlands to prevent unauthorized movement of people across the border. The fences covered 300 kilometres and consisted of several strands of copper wire, backed with barbed wire, and energized to several thousand