In these cases of combustion, oxygen seems to act an important part, and by combining with the hydrogen of oil to excite a chemical action which may be considered the immediate cause of the phenomenon. Saw-dust, and other vegetable matter, has been occasionally excited into flame by the action of the concentrated mineral acids; we have been lately informed by _Mr. Parkes_, that a fire took place some years since in his chemical manufactory, in consequence of the leakage from a carboy of nitric acid. Several instances are also on record of fires having been occasioned by the sudden slacking of quicklime; _Theophrastus_ relates an instance of a ship which was loaded in part with linen, and in part with quicklime, having been set on fire by water that was accidentally thrown over the latter, and that the vessel was in consequence entirely consumed. In the _Journal de la Haute Saone_ there is an account of the burning of a barn, one of the partitions of which being wood had caught fire from a quantity of quicklime, intended for the repair of the premises, having been carelessly thrown against it. In this country a similar accident happened in the last winter at Edmonton, near London; the flood, consequent upon a heavy fall of rain, made its way among the quicklime in a bricklayer’s premises, which took fire and were burnt. There still remains for notice another source of spontaneous burning,—the ignition of _Pyrites_, and that of cinders from the furnaces of glass-works, from exposure to air and moisture; it was in this manner that the ship _Ajax_ was supposed to have been consumed, from the spontaneous combustion of coal, abounding in _Pyrites_. HUMAN COMBUSTION.