KEY: NC O = N. C. Officer. M = Miners. P = Picks. MP = Miners' Picks. P-p = Push-picks. Sh = Shovels. MS = Miners' Shovels. MT = Miner’s Truck. F-l = Field-levels. M-r = Measuring-rod 6´. T-l = Tracing-line. M S = Mauls or Sledges. CB = Canvas Buckets. R-l = Rope-ladder. W-b = Wheel-barrows. MB = Miners' Bellows. Pr. = Progress, ins. per. hour. -------------------+-----------+---------------------------------------------------------------- | Men. | Tools. Kind of Gallery, +----+------+---+---+---+---+---+-----+---+---+---+---+---+---+---+---+------ etc. |NC O| M | P | MP|P-p| Sh| MS| MT |F-l |M-r|T-l|M S|CB |R-l|W-b|MB | Pr. -------------------+----+------+---+---+---+---+---+-----+----+---+---+---+---+---+---+---+------ Great gallery or } | | | | | | | | | | | | | | | | | Blinded gallery } | 1 |12[14]| 4 | 2 | 2 | 8 | | | 1 | 1 | 1 | 1 | | | 4 | | 12 Common gallery | 1 | 4 | | 1 | 1 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | | | | 1 | 12 Half gallery | 1 |4[15] | | 1 | 1 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | | | | 1 | 16 Branch gallery | 1 |4[15] | | 1 | 1 | 2 | 1 | 1 | 1 | 1 | 1 | 1 | | | | 1 | 24 | | | | | | | | | | | | | | | | |{ 30 Small branch | 1 | 3 | | 1 | 1 | | 2 |1[16]|[17]| 1 | 1 | 1 | | | | 1 |{ to | | | | | | | | | | | | | | | | |{ 36 | | | | | | | | | | | | | | | | | Shaft | 1 |4[18] | | 1 | 1 | 2 | 1 | | 1 | 1 | 1 | 1 | 1 | 1 | | |{ 18 | | | | | | | | | | | | | | | | |{ 24 -------------------+----+------+---+---+---+---+---+-----+----+---+---+---+---+---+---+---+------ VENTILATION OF MINES. =57.= The gases resulting from firing mines and from the lamps, bodies, and candles of the miners so vitiate the air in galleries that, unless means for ventilating them are adopted, the miners must eventually abandon them or become asphyxiated. In ordinary circumstances, when no powder gases are present, a gallery cannot be driven safely more than 60 feet without ventilation. The measures adopted for ventilating galleries consist, 1st, in forcing in fresh air; 2d, in drawing out foul air; and, 3d, in assisting the natural diffusion and circulation of the air through them.