or charred pitcoal, is prepared for the smelting of iron ore, by igniting the coals piled up in long ridges in the open air, and closing in the cinders with earth, when brought to a glowing red heat. For the use of the manufacturers, the method hitherto most in practice has been to burn the small or screened coal in conical ovens, built of firestone or brick, the floor being generally about six feet diameter, and the oven eight feet high, while an aperture of eighteen inches diameter is left at top. The small coal is thrown in to the depth of fifteen inches or more, and then ignited. The oven door is at first kept open, and the hole at the top left uncovered till the mass is red-hot. The door is then closed, and by degrees the hole at the top is covered over by two large flat stones, gradually approaching each other, when the whole is left to cool. When sufficiently cooled, it is drawn out with long iron rakes, and the mass is found to have assumed a rude columnar arrangement, not much unlike starch. The oven is immediately charged again with small coal, which the heat remaining in the floor is found sufficient to ignite, and so the operation goes on. In both the above ways good coaks are made, but the volatile products are lost. To save these, Lord Dundonald proposed to burn the coals in a close furnace, to which he adapted an apparatus for conveying the coal-tar, with the ammoniacal products, into proper recipients. About the same time Baron Van Hassa, a German, constructed works in the neighbourhood of Newcastle, for distilling the small coal in large cast-iron cylinders, upon the plan which has since been adopted in the gas works; except that the soot from the furnace fires is, at Newcastle, during a certain period of the combustion, before any gray ashes have begun to arise, conveyed into a chamber contrived for the purpose, and collected for lamp-black; an economical practice, which does not appear to have been carried into the gas works. It is probable that, as the practice extends of lighting our towns with carburetted hydrogen gas, most of the coak used in manufactures will be furnished in this way; but as the coak thus produced will probably contain more sulphur, it is not likely that it will be fit for the smelting of iron ore; the coak for which must, therefore, continue to be made in the old way.