Early iron and steel, of course, were comparatively rare, so much so as to be available only for implements of war and for particular purposes. Moreover, all of the steel made was of the high carbon, hard variety, none of it being of the low carbon sort which we know as the soft or mild steels. The latter have all come since the invention of the Bessemer process in 1855 and the Siemens-Martin (the open-hearth) process of a few years later. As you will remember the next development in the iron industry was the use of the larger blast furnace and much more fuel, with higher temperatures and the production of cast iron which, by reason of the absorption of considerable carbon from the fuel, was fluid enough to run out of the furnace. And, as you also know, this blast furnace metal has come to be the great intermediate product in what has come to be known as the _Indirect Process_ of making iron and steel. [Illustration: PICKLING IN WEAK ACID EXPOSES THE “FIBERS” OF WROUGHT IRON ] As pig iron contains 3½% or more of carbon, while wrought iron has none or comparatively little of this embrittling element, any process for converting the pig iron into wrought iron must eliminate the carbon. Following the advent of pig iron as a commercial product several furnaces and processes were developed to turn it into wrought iron. All of these were based upon the elimination of the carbon by _oxidation_, which means the burning of the carbon in presence of oxygen of the air. The best known ones were the Walloon or Swedish Lancashire process, the South Wales process, the Finery Fire, the Running-Out Fire and the Charcoal Finery or Knobbling process. The Walloon furnace, largely used in Sweden, is shown in the illustration on page 94. While by the process generally used to-day wrought iron is more easily and cheaply produced, it must be said that by the processes above named has been made as fine iron as has ever been produced. The Sheffield manufacturers, whose high grade steel made by the crucible process, is so widely and favorably known for cutlery, tools, etc., in many cases yet demand the Walloon process iron made from high grade Swedish ores as the starting point for their product. [Illustration: BAR IRON WILL STAND SEVERE BENDING EVEN AFTER IT HAS BEEN NICKED ] [Illustration: SWEDISH WALLOON FURNACE One of several types of furnaces that preceded the Reverberatory. Some of them are still used. ]