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40 (XL) — 1929-1930
Oakdale Colliery Visited, 288.
Occurrence of Coal, 337.
Occurrence, Water, Occasional, 226.
Officials, Presentations, 328.
Ohm's Law, 133, 152.
Old Workings, Plans, 297.
Order, Safety-lamps, 284.
Ore Transport, 293.
Ouston Pit's Record, 136.
Output, Coal, 8, 12, 21, 42, 64, 80, 88, 103, 120, 139, 151, 163, 168, 184, 195, 200, 215, 232, 248, 264, 283, 295, 311, 327, 352, 358, 369, 387, 396.
Oxygen, Properties, 67, 258.
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