A system of mine development that is suitable for inclined, and perhaps faulted, coal seams. Main stone headings are driven, at predetermined levels, from the winding shaft to intersect and gain access to the seams to be developed. The stone headings, or horizons, are from 100 to 200 yd (91.44 to 182.88 m) vertically apart, depending on the seams available and their inclination. The life of each horizon ranges from 10 to 30 years. Connections between horizons at inby points are by staple shafts or drivages in the coal.