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explpsions of fire-damp. Gauze made ofbrass wire, one-fiftieth of an inch in thick-ness, and containing only ten apertures tothe inch, or 100 apertures in the squareinch, employed in the usual way as a guardof flame, did not communicate explosion ina mixture of 1 part of coal gas and 12parts of air, as long as it was cool, but assoon as the top became hot, an explosiontook place.

“ A quick lateral motion likewise enabledit to communicate explosion.

“ Gauze made of the same wire, con-taining 14 apertures to the inch, or 196to the square inch, did not communicateexplosion till it became strongly red hot,when it was no longer safe in explosivemixtures of coal gas; but no motion thatcould be given to it, by shaking it in a closejar, produced explosion.

“ Iron wire gauze of one-fortieth, andcontaining 240 apertures in the square inch,was safe in explosive mixtures of coal gas,till it became strongly red hot at the top.

“ Iron wire gauze of one-fiftieth, and of24 apertures to the inch, or of 576 to thesquare inch, appeared safe under all cir-