yards to other furnaces to be made into steel. This time they are melted in big, pear-shaped pots fifteen feet high and eight feet across. The pots of thick boiler-plate bolted together, are lined with fire clay and swung on beams so they can be tipped over. As the pig iron in the pot melts, an air blast is forced through and makes it boil furiously. Certain things are put into it to change the iron to steel. As it boils crimson flames leap in the air. The flames turn orange, then yellow, then white, then an electric blue-white. At that point the pot is tipped and the dazzling, blue-white, molten steel is poured into oblong moulds.
Each block, or ingot, of steel has enough in it to make a steel rail one hundred feet long. When the ingot is cold it is sent over the yard railroad again to the rolling mill. There it is heated to a bright red, and as soft, nearly, as putty. Tumbled from the furnace onto a travelling table of iron bars, it is suddenly gripped by enormous iron rollers like some giant clothes wringer with grooves in the rolls, and forced through the grooves. There it is squeezed and lengthened and sent on through one smaller hole after another.
The old forge of Vulcan in the burning mountain could not have been hotter, or full of such thunderous crashes, of quivering air and flying sparks as a modern rail mill. The workmen are big men; they are stripped to the waist, and streaming with sweat. With long iron rods they turn and push and guide the glowing blocks of steel from one set of rolls to another. They never speak, for no human voice could be heard in the roar and crash. The last rolls begin to shape the lengthened block into a rail with a broad flat bottom, a curved top and grooved sides. It grows longer and longer, and more perfectly shaped, as it nears the end of the journey. At last it is laid on an iron grating to cool.
Today iron and steel are taking the place of wood and brick and stone in building ships, bridges and fireproof skyscrapers. They are used in the finest palace cars, in making oil tanks, service pipes, bath tubs, expanded lath for plastering, pressed sheets for ceilings and walls, and for lining tunnels. The subway, or underground railway in New York is a double steel tube. Bridges and elevators are hung on wire rope. In old, old times men used stone hatchets. That was called the stone age. Then there was a bronze age when copper was made. Our time is called the iron age because we have learned to do so many things with iron. See Iron, Steel, Rolling Mills.
