Among the various improvements for expeditiously and effectually converting crude into malleable iron, the process of Mr. Cort seems to possess advantages. The cast iron is melted in a reverberatory furnace, and the flame of the combustible is made to act upon the melted matter. It is stirred during this operation, by which means, every part is exposed to the air. A lambent blue flame begins to appear in about an hour, and the mass swells. The heat is continued about an hour longer; and, by this time, the iron acquires more consistency, and finally congeals. While still hot, it is next hammered by powerful tilt-hammers. This is called the _puddling_ process. Iron, obtained in this way, is not however pure; for it contains either some of the other metals, or oxygen, carbon, silicon, or phosphorus. When small pieces of iron are stratified in a crucible with charcoal powder, and exposed to a strong heat for eight or ten hours, they are converted into steel. Steel is brittle, resists the file, cuts glass, and affords sparks with flint. It loses its hardness by ignition and cooling. It is malleable at a red heat. It melts at 130 degrees of Wedgwood. By being repeatedly ignited in an open vessel, it becomes, by hammering, wrought iron. Natural steel is that which is formed, by converting the ore first into cast-iron, and exposing it to the action of a strong heat, while the melted scoriæ float on its surface. This steel is inferior to the others. Steel of cementation is formed, on a large scale, by stratifying bars of iron with charcoal, in large earthen troughs or crucibles, the mouths of which are closed with clay. These troughs are put in furnaces, and, in eight or ten days, the process is finished. This is also called blistered steel, on account of the appearance of its surface. The tilted steel is that which is beaten out into small bars by the hammer. When broken, and the pieces again united by welding in a furnace, and made into bars, it is then called German or shear steel. Cast steel is considered the most valuable of all the varieties; and is used for the manufacture of razors, surgeons' instruments, &c. It is, besides, more fusible than common steel, and for that reason, cannot be welded with iron. It is made by melting the blistered steel, in a close crucible, along with pounded glass, and charcoal powder. It may also be formed by melting together 30 parts of iron, 1 part of charcoal, and 1 part of glass. Equal parts of chalk and clay, put with iron in a crucible, will also produce it.