ASDIC units laid on the seabed to detect U-boats and enemy surface vessels trying to enter the Forth from shortly before the Second World War until 1946. Since 1956 the isle has been dedicated as a National Nature Reserve and managed by the Nature Conservancy Council, now NatureScot, although until 1989 it was actually owned by the Northern Lighthouse Board. Lighthouses A coal-fired beacon was established in 1635 (or 1636) by James Maxwell of Innerwick, and John and Alexander Cunningham, who charged shipping a tonnage-based fee. This was originally 2 Scottish shillings per ton for Scottish ships (equivalent to two pence sterling) and twice this amount for non-local shipping per voyage, but was reduced to 1 shilling and sixpence, and three shillings respectively in 1639 with some shipping entirely exempt during the summer. The beacon, the first permanently manned one in Scotland and considered at the time to be one of the best in existence, used around 400 tons of coal per year, requiring three men to look after it. One of the three lightkeepers, George Anderson, and his wife Elisabeth, along with five of their six children were suffocated by fumes in January 1791. Their eleven-month-old daughter Lucy was discovered alive three days later. Ash and clinker had piled up beside the beacon tower over the previous ten years and had reached the window of keepers' room, and was set smouldering by coals falling from the beacon. The light was sometimes hard to recognise, for example a 36-gun fifth rate captured from the French in 1780 and were wrecked near Dunbar on the night of 19 December 1810 because their navigators had mistaken a lime kiln on the mainland coast for the beacon. The Northern Lighthouse Board purchased the island in 1814 from the Duke and Duchess of Portland for 60,000 pounds, by which time the beacon was the last remaining private lighthouse in Scotland. A proper lighthouse was built on the island in 1816 by Robert Stevenson. and is an ornate gothic tower on a castellated stone building designed to resemble a castle, high and with accommodation for three light keepers and their families, along with additional space for visiting officials. The new lighthouse started operating on 1 September 1816, and is now a listed building. It was upgraded in September 1836, when a new light and refractor lens was fitted, and further extensive work took place in