| 41. | The system in Bidar is said to extend two kilometers and originally had 21 vertical shafts.
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| 42. | :: The vertical shafts are called light wells.
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| 43. | Many lighthouses had vertical shafts in them so the weights could drop the height of the tower.
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| 44. | It is the continent's deepest vertical shaft coal mine at 2, 140 feet ( 642 meters ).
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| 45. | In 1928, construction of four vertical shafts was completed to continuously provide fresh air to the tunnels.
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| 46. | At the end of the access tunnel, two vertical shafts lead down to the base tunnel level.
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| 47. | Coal was mined through vertical shafts accessing inclined slopes following the dip of the Pittsburgh coal seam.
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| 48. | Expanding foam is used primarily with vertical shafts where the use of the shaft is no longer desired.
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| 49. | Another is for buildings to have multiple vertical shafts, called risers, equipped with wiring open to all carriers.
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| 50. | The vertical shafts are 15 to 17 metres ( before restoration was initiated ) deep on an average.
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