Note 39 — Chapter XXIII · ON MINES IN GENERAL.

Mr. Samuel Plimsoll (‘Letters on the Iron Trade,’ Times, February 10, 1868) informs us that in the Belgian coal mines the ventilation is carried on in a more economical and effective manner. Here no furnaces are lighted at the bottom of the upcast, because one-twentieth of the coal required for a furnace will make steam for an engine to work fans which act somewhat in the manner of huge paddle-wheels in steam-ships, and by rapid rotation over the shaft produce a draught which the incoming air rushes to meet, and thus powerfully promote ventilation. These fans they can work and control, and are therefore independent of those atmospheric influences to which some of our greatest calamities have been ascribed—the damp, heavy atmosphere of early winter. In the great colliery of Sacrée Madame, near Charleroi, one of these fans will draw 34,000 cubic metres (about 918,000 cubic feet) per minute.