Many other large firms now compete for their share of the trade; and the extent to which it has grown, the number of furnaces constantly at work, and the quantity of steel cast into ingots, to be tilted or rolled for the various purposes to which it is applied, have rendered Sheffield the greatest laboratory in the world of this valuable material. Of the total quantity of cast-steel manufactured in England, not less than five-sixths are produced there; and the facilities for experiment and adaptation on the spot have enabled the Sheffield steel-makers to keep the lead in the manufacture, and surpass all others in the perfection to which they have carried this important branch of our national industry. It is indeed a remarkable fact that this very town, which was formerly indebted to Styria for the steel used in its manufactures, now exports a material of its own conversion to the Austrian forges and other places on the Continent from which it was before accustomed to draw its own supplies. Among the improved processes invented of late years for the manufacture of steel are those of Heath, Mushet, and Bessemer. The last promises to effect before long an entire revolution in the iron and steel trade. By it the crude metal is converted by one simple process, directly as it comes from the blast-furnace. This is effected by driving through it, while still in a molten state, several streams of atmospheric air, on which the carbon of the crude iron unites with the oxygen of the atmosphere, the temperature is greatly raised, and a violent ebullition takes place, during which, if the process be continued, that part of the carbon which appears to be mechanically mixed and diffused through the crude iron is entirely consumed. The metal becomes thoroughly cleansed, the slag is ejected and removed, while the sulphur and other volatile matters are driven off; the result being an ingot of malleable iron of the quality of charcoal iron. An important feature in the process is, that by stopping it at a particular stage, immediately following the boil, before the whole of the carbon has been abstracted by the oxygen, the crude iron will be found to have passed into the condition of cast-steel of ordinary quality. By continuing the process, the metal losing its carbon, it passes from hard to soft steel, thence to steely iron, and last of all to very soft iron; so that by interrupting the process at any stage, or continuing it to the end, almost any quality of iron and steel may be obtained. One of the most valuable forms of the metal is described by Mr. Bessemer as "semi-steel," being in hardness about midway between ordinary cast-steel and soft malleable iron. The Bessemer processes are now in full operation in England as well as abroad, both for converting crude into malleable iron, and for producing steel; and the results are expected to prove of the greatest practical utility in all cases where iron and steel are extensively employed.