acting governor; it was only the lucky arrival of an East India Company fleet under the command of Captain William Basse that freed Keigwin. By 1675, the part-time recruitment of settlers in a Militia enabled the permanent garrison to be reduced to 50 troops. On leaving the University of Oxford, in 1676, Edmond Halley visited Saint Helena and set up an observatory with a aerial telescope and observed the positions of 341 stars in the Southern hemisphere. His observation site is near St Mathew's Church in Hutt's Gate, in the Longwood district. The 680m high hill there is named for him and is called Halley's Mount. Amongst the most significant taxes levied on imports was a requirement for all ships trading with Madagascar to deliver one slave. Slaves were also brought from Asia by incoming shipping. Thus, most slaves came from Madagascar and Asia rather than the African mainland. By 1679, the number of slaves had risen to about 80. An uprising by soldiers and planters in 1684 during the governorship of John Blackmore (1678–1689) led to the death of three mutineers in an attack on Fort James and the later execution of four others. The formation of the Grand Alliance and outbreak of war against France in 1689 meant that for several years ships from Asia avoided the island for fear of being attacked by French men-of-war. Soldiers at the end of their service thereby had restricted opportunities to obtain a passage back to Britain. Governor Joshua Johnson (1690–1693) also prevented soldiers smuggling themselves aboard ships by ordering all outgoing ships to leave only during daylight hours. This led to a mutiny in 1693 in which a group of mutineer soldiers seized a ship and made their escape, during the course of which Governor Johnson was killed. Meanwhile, savage punishment was meted out to slaves during this period, some being burnt alive and others starved to death. Rumours of an uprising by slaves in 1694 led to the gruesome execution of three slaves and cruel punishment of many others. The clearance of the indigenous forest for the distillation of spirits, tanning and agricultural development began to lead to shortage of wood by the 1680s. The numbers of rats and goats had reached plague proportions by the 1690s, leading to the destruction of food crops and young tree shoots. Neither an increase on duty on the locally produced arrack nor