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volume of air, takes fire at the lowest visibleheat of iron and charcoal; and the case isthe same with sulphuretted hydrogene.

I found that when 6 of air and 1 of fire-damp were exploded over water by a strongelectrical spark, the explosion was not verystrong, and, at the moment of the greatestexpansion, the volume of the gas did notappear to be increased more than one-half*.

I mixed azote and carbonic acid in dif-ferent quantities with explosive mixturesof fire-damp, and I found that even in verysmall proportions they diminished the velo-city of the inflammation. Azote, when mixedin the proportion of 1 to 6 of an explosivemixture, containing 12 of air and 1 of fire-damp, deprived it of its power of explosion;when 1 part of azote was mixed with 7 ofan explosive mixture, only a feeble blueflame slowly passed through the mixture.

1 part of carbonic acid to 7 of an explo-sive mixture deprived it of the power ofexploding; so that its effects are more re-

* This appears the expansion when the tube is verysmall; in larger tubes, it is considerably more. Thevolume of the gas appears at least tripled during theexplosion.