on satellite photographs. At the time of Édouard Cortier's visit in 1906 the mining area was 3 km south of the ksar; in the 1950s the active mines were located in an area 5 km from the ksar, while the current mines are at a distance of 9 km. In 2007-2008 there were around 350 teams of miners, with each team usually consisting of an experienced miner with 2 labourers, giving a total of around 1000 men. The men live in primitive huts constructed from blocks of inferior quality salt and work at the mines from October to April, avoiding the hottest months of the year, when only about 10 of them remain. The slabs are transported across the desert via the oasis of Araouane to Timbuktu. In the past they were always carried by camel, but recently some of the salt has been moved by four-wheel drive trucks. By camel the journey to Timbuktu takes around three weeks, with each camel carrying either four or five slabs. The typical arrangement is that for each four slabs transported to Timbuktu, one is for the miners and the other three are payment for the camel owners. Up to the middle of the 20th century the salt was transported in two large camel caravans (azalaï), one leaving Timbuktu in early November and a second leaving Timbuktu in late March, at the end of the season. Horace Miner, an American anthropologist who spent seven months in the town, estimated that in 1939-40 the winter caravan consisted of more than 4,000 camels and that the total production amounted to 35,000 slabs of salt. Jean Clauzel records that the number of slabs reaching Timbuktu increased from 10,515 in 1926 to 160,000 (4800 t) in 1957–1958. However, in the early 1970s the production decreased, and at the end of the decade was between 50,000 and 70,000 slabs. Prison A military post and a prison were built at Taoudenni in 1969 during the regime of Moussa Traoré. The prison was used to detain political prisoners until 1988, when it was closed. Many of the prisoners were government officials who had been accused of plotting against the regime. The prisoners worked in the salt mines and many of them died. To the east of the ruins of the prison building is a cemetery containing 140 individual graves, of which only a dozen have names. They include: Yoro Diakité,