1909. Hingston Down mine (which worked westwards towards Kit Hill). This was a very early mine, and evidence shows it may have started in the 17th century: it closed in 1885. South Kit Hill Mine was worked from 1856 to 1884. Atomic Energy Authority In 1877 a company called Kit Hill Tunnel Ltd began work on both the south and north sides of the hill to create a tunnel which would be long. The southern portal was at Silver Hill, and that at the north was near a small mine called Excelsior. However, due to the toughness of the underlying bedrock, progress was costly and slow, and ceased about a year later. In 1881 a new company named Kit Hill Great Consols took over the setts of Kit Hill United and Excelsior mine. They deepened the North Engine Shaft to 112 fathoms and lengthened the tunnel running south to meet it. However, this too was proving too costly, and wound up in 1885, before it was half-way complete. Several later attempts were made to extend the Excelsior Tunnel, but by 1938, it was still only long. However, in 1959 the Atomic Energy Authority took over operations, and used the tunnel for underground explosions. The activities were part of Operation Orpheus, and the Kit Hill events were the first part: Phase A: Small charges fired in a diameter cavity in granite and shale at depths of 100 to in the Excelsior Tunnel at Kit Hill. Phase B: Participation in the Operation Cowboy tests, where charges of would be detonated in diameter cavities at depths of in a salt mine in Louisiana, United States. Phase C: The tests at Greenside Mine in Cumbria, where a decoupled test and a coupled test would be carried out in andesite rock at a depth below surface of and the results compared. The charge sizes were chosen so that if the decoupling worked as predicted, the seismic signals would be similar in intensity. Railways Construction of The Tamar, Kit Hill & Callington Railway started in 1864. The name was later changed to the East Cornwall Mineral Railway, and the line opened in 1872. Seven and a half miles long, it ran from Calstock's river frontage, past Kelly Quay & Drakewalls and the Gunnislake quarries, along the northern flank of Hingston Down to below Kit Hill at Kelly Bray, where an inclined tramway connected with it. It