Messes. Editors—I enclose a paragraph ut from the Evening Bulletin of Saturday last, especting the spontaneous ignition of pow-lered charcoal when damp. This hasgreatly iurprised me, and I cannot credit it. In seve-al places in my woolen mill where steam ripes were exposed to the cold air, I protected ;hem by wooden boxes filled with powdered ;harcoal; and in one place particularly, I mow that the dropping water from a cock iept the charcoal wet, yet there has been no gnition. I preferred charcoal to sawdast or liemp, or cotton, for the reason that I believed ;he heat of the pipes would not ignite it, nor lampness produce that effect ; but if certain hemists of Philadelphia are correct, there is langer, and I beg your opinion on the subject, having confidence in your judgment. * * * Norristown, Pa., December, 1857. [The following is the paragraph referred to :— " The Origin.—Fire Detective Blackburn lias made a careful investigation into the cause of the recent fire at the freight depot of Davis & Steel, Market st., above Eighth. It seems that there were several bags of powdered charcoal stored in the car-house; and several chemists whom Mr. Blackburn has consulted state that powdered charcoal, when damp, is liable to spontaneous combustion. The atmosphere was very wet at the time of the fire, and the coal, no doubt, absorbed considerable moisture. As the fire made its first appearance in the precise spot where these bags were stored, the strong probability is that it originated from spontaneous combustion." It is our opinion that the fire alluded to in the above extract was not caused by the spontaneous combustion of powdered charcoal ; and wo will hold to this opinion until some of those Philadelphia chemists or other persons afford us satisfactory proof that charcoal in powder, either in moist weather or when wet with water, will spontaneously ignite and burn. We have seen charcoal dust exposed for long periods of time to moisture and the atmosphere, and never knew an instance of spontaneous combustion caused thereby. We do not doubt that impurities (such as pyrites) ground with charcoal into dust, may, when moistened with water, generate sufficient heat to induce spontaneous combustion in the coal; but we mean that good common charcoal could not have produced the results specified in the aboy paragraph. There are many curiosities in chemistry, and the above may be one of them ; but it has generally been held that carbon-charcoal will not burn, nor unite chemically with oxygen under a red heat, to produce combustion.—Eds.