We have received from one of our correspondents—S. M. Parsons, of Waukan, Wis.— the account of a peculiar explosion of an air chest which took place a few weeks ago at the Vermilion Blast Furnace of that place. Dr. Tilden, one of the proprietors, informed him that the furnace and hearth were of the common form with one tweer, using charcoal for fuel with hot blast smelting a mixture of bog aud other iron ore. The furnace had run over thirty days, and was stopped half an hour to draw off the metal. The instant it was started again, the air chest exploded with a most violent report, and doing considerable damage. It was situated one hundred feet from the furnace between two cylinder bellows, with which it was connected by swing valves. The pipe connecting it with the furnace passed back and forth under the boilers where it leaked a little ah-, and the tweer also leaked some water at its mouth. Various cases of explosions are on record as having been caused by leaky tweers, and in all likelihood this was the cause of this explosion. Water falling upon red-hot charcoal, or iron will be decomposed, and the liy-drogen gas set free. In this case, water from the tweer may have been decomposed, and the hydrogen may have passed into the leaky air-pipe, thence into the air chest, and mixed with the oxygen of the air, thus forming a violently explosive compound gas easily ignited by the most minutu spark.