<P> On 28 September 1971, the lighthouse was automated . A reinforced concrete helipad was constructed at the same time to enable maintenance visits in heavy weather . The light is produced by burning acetylene gas and has a range of 17 nautical miles; 20 miles (32 km). It is now monitored from the Butt of Lewis and the shore station has been converted into flats . </P> <P> Other than for its relative isolation, the lighthouse would be relatively unremarkable, were it not for the events which took place just over a year after it was commissioned . </P> <P> The first hint of anything untoward on the Flannan Isles came on 15 December 1900 . The steamer Archtor on passage from Philadelphia to Leith passed the islands in poor weather and noted that the light was not operational . The ship suffered the misfortune to run aground on Carpie Rock in the Firth of Forth some time after passing the lighthouse and after the struggle to save the ship, the fact of the lighthouse light being unlit was not reported on arrival at Oban for some time, the ship's master, Captain Holman, being distracted by the damage to his ship, and the procedures for dealing with her on arrival in port . The island lighthouse was manned by a three - man team (Thomas Marshall, James Ducat, and Donald MacArthur), with a rotating fourth man spending time on shore . The relief vessel, the lighthouse tender Hesperus, was unable to set out on a routine visit from Lewis planned for 20 December due to adverse weather and did not arrive until noon on Boxing Day (26 December). On arrival, the crew and relief keeper found that the flagstaff was bare of its flag, none of the usual provision boxes had been left on the landing stage for re-stocking, and more ominously, none of the lighthouse keepers were there to welcome them ashore . Jim Harvie, captain of Hesperus, gave a strident blast on his whistle and set off a distress flare, but no reply was forthcoming . </P> <P> A boat was launched and Joseph Moore, the relief keeper, was put ashore alone . He found the entrance gate to the compound and main door both closed, the beds unmade, and the clock stopped . Returning to the landing stage with this grim news, he then went back up to the lighthouse with Hesperus's second - mate and a seaman . A further search revealed that the lamps were cleaned and refilled . A set of oilskins was found, suggesting that one of the keepers had left the lighthouse without them, which was surprising considering the severity of the weather on the date of the last entry in the lighthouse log . The only sign of anything amiss in the lighthouse was an overturned chair by the kitchen table . Of the keepers there was no sign, neither inside the lighthouse nor anywhere on the island . </P>

When did the events at flannan isle occur