It was not until the middle of the 14th Century that a blast furnace, crudely similar to those we have to-day, was first built and with it a temperature was obtained that was high enough to turn the metal into a liquid which could be cast in molds. Charcoal continued to be the fuel used until about four centuries later, when Abraham Darby discovered that by baking coal to remove its free gases, he could produce a new fuel known as coke which was a good substitute for charcoal. This gave a wonderful impetus to the iron industry in England where there were ample deposits of coal adjacent to the iron mines. Shortly after that, Mr. Henry Cort of Gasport, England, invented the processes of puddling and rolling the product of the blast furnace, thus converting the iron into a tough, malleable metal. ALLOYS OF CARBON AND IRON We must pause here to learn the difference between cast iron, wrought iron and steel. Iron, as we know, has a high affinity for oxygen. When exposed to air and moisture it oxidizes, rusts very quickly. The iron we find in nature is largely oxidized. In other words, it is rusty. It is also found in combination with other elements as well. The object of putting iron ore through a furnace is to rid it of oxygen and this is most readily accomplished by melting it in a carbon fire. The highly heated carbon combines with the oxygen and passes off as carbon dioxide and carbon monoxide gas. But a certain amount of carbon unites with the iron and it is this alloy of carbon and iron that makes cast iron so stiff and brittle. The less carbon present the softer is the metal and pure iron is very ductile. It was to rid cast iron of its carbon content that Cort invented the puddling process. As the metal came out of the blast furnace it ran into a “reverberatory” furnace where, without coming in contact with coke or other carbon fuel, it was exposed to flames from an adjoining furnace which burned out the carbon, and then the carbon-free iron was cast into large pieces known as blooms which were hammered to rid them of slag. The final product was known as wrought iron. Wrought iron then differs from cast iron in having no carbon. Steel, on the other hand, stands half way between wrought iron and cast iron in having a small percentage of carbon. How steel is made will be described later. MECHANICAL HANDLING OF ORE