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 is generally about six feet diameter, and the oven eight feet high, an aperture of 18 inches diameter being left at top. The small coal is thrown into the depth of 15 inches or more, and then ignited. The oven-door is at first kept open, and the hole at top left uncovered till the mass is red-hot. The door is then closed, and, by degrees, the hole at top 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 apparatus for conveying the coal-tar, with the ammoniacal products, into proper recipients. About the same time, Baron Von Haak, 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-light works; except that the soot from the furnace fires is, at Newcastle, during a certain period of the combustion, before any grey 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; and it is probable, that, as the practice of lighting our great towns with the carburetted hydrogen gas extends, most of the coal used in manufactures will be furnished in that way; but, as the coal 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.