Depblogijlicated Air . 193

first papers sent to the Royal Society, andbefore I formed them into a volume. Forthe peculiar characters of this kind of air willbe found in my description of that whichI extracted from salt petre, and also of thatfrom alum. See my Observations on Air,Vol. I. p. 155. I there say " All kinds" of factitious air, on which I have yet" made the experiment, are equally noxi-" ous, except that which is extracted from" fait petre, or alum; but in this even a" candle burned just as in common air." In one quantity which I got from fait“ petre a candle not only burned, but the" flame was increased, and something was" heard like a hijjing , similar to the de-" crepitation of nitre in an open fire. This“ experiment was made when the air was“ fresh made, and while it probably con-" tained some particles of nitre, which“ would have been deposited afterwards.”This hijjing , however, was certainly owingto the avidity with which this pure. airseized upon the phlogiston of the bodiesignited in it; and that property would, notO have