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COAL MINES OF

that the air was sent in through what he terms'safety canals , or close concentric metallic cy-linders fitting within one another, and leavingan aperture between each of an inch and seven-tenths long, and from one twenty-fifth to onefortieth of an inch in width. The chimney maybe protected in the same way; but if Sir H.Davy is satisfied that the fire-damp or combus-tible principles'is destroyed within the lantern,and does not ascend much above the lower endof the chimney, why is this necessary ? Uponthis principle various lamps are applicable witha little alteration.

The third lamp is a close lamp or lanternhaving the air apertures covered with brasswire gauze, of one two-hundredth of an inchin thickness, having apertures of one one hun-dred and twentieth of an inch.* This preventsexplosion, and, should the fire-damp inflame inthe lantern, will not suffer any communicationwith the surrounding air: unless this very finecovering is well protected by some strongermaterial I should doubt its security very much

* These are the proportions mentioned in Sir H, Davy’spaper to the Royal Society; but in an abstract publishedin the Edinburgh Review, the apertures are stated at onetwentieth of an inch, and the thickness of the wire atone sixtieth. When Doctors disagree, who shall decide !