“It’s a chemical process. When the air strikes the hot metals the oxygen unites with them, and they burst into flame. The whole process takes between fifteen and twenty minutes.”
“I am very sure,” said Dr. Crandon, “that I shouldn’t like to work here.”
“When we get to the open hearth process, which is the rival of the Bessemer,” said Mr. Prescott, “I expect that none of you will want to work there.”
“For my part,” said John Bradford, slowly, “I prefer Prescott mill.”
“So do I,” said Billy.
“Which reminds me,” said Mr. Prescott, “to tell you that I have been looking at some machines to help in the foundry. They will help about lifting and ramming; but they won’t do away with the work of men.
“Here we are, gentlemen, before a Siemens-Martin open hearth. This is a continuous process. It was evolved by Sir William Siemens, a German-English engineer, and his brother. Then a man named Martin, a Frenchman, I understand, found a way to mix the iron and steel that are put on the hearth, so it bears both the names.
“We’ll just look in. It is a large, shallow basin, made of bricks, partly filled with iron. Both hot air and gas are burned on top of the iron. The process takes seven or eight hours; but it produces larger quantities of steel than the Bessemer converters can do.
“Then, too, it furnishes all kinds of iron and steel, for they sample it as it burns, and draw off the steel at any percentage of carbon that they want.
“Cast iron has a great deal of carbon in it; steel has much less; and wrought iron has almost none.