"I want you to help me to think about cast-iron again," said Fred. "First of all, why do we call it cast- iron, Norah?""The iron is melted into a liquid," said Norah, "and poured or cast into a mold.""Teacher showed us," said Willie, "that cast-iron is very useful in its own way, but this is only because it is not like other iron. It fuses or melts easily and with less heat than wrought iron.""Yes," said Fred, "and when it is cooling in the mold, it swells out and presses into every corner. It must take the exact shape of the mold.
