In a paper read before the British Society of Arts, by Charles Sanderson, upon the subject of Iron, he remarked that although the blast-furnace is the most effective and also the most economical for reducing iron ore, yet we find that there is an actual loss equal to 80 per cent of the effectual usefulness of the fuel. This fact is arrived at from the theory which he laid before them of the formation of gases in the furnace, taking the melting point of pig-iron at 2,192 Fah. The fuel used, together with the blast injected into the furnace, will give the quantity of carbonic oxyd, light hydrogen, &c, which, when burned with heated air, would be sufficient to reduce or melt a given weight of iron from its ore, which in theory is estimated at between 16 and 17 per cent of the value of the fuel consumed. These gases, so largely produced, are now collected in many works by means of pipes variously arranged, and inserted a few feet below the mouth of the furnace. They are used mixed with a certain portion of atmospheric air, as a fuel for raising steam, heating the blast for the furnace, and (on the Continent) or the purpose of puddling ; also for drying and carbonizing the ore prior to its being charged into the furnace. If these gases are taken as they arise from the furnace, he sees no objection to their being applied to useful purposes, but he does not object to even the least forcible means being used to draw them from it. No current ought to be created in any apparatus which may be formed for conveying these gases, since it would cause them to pass too rapidly through the furnace, and thus prevent them from producing their full effect upon the materials through which they are made to pass. This utilization of the waste gases is highly interesting, and presents a wide field for application, besides which there is n evident economy to be obtained from their use, provided they are properly withdrawn from the furnaoe.