“And I know, too, that Sir Isaac Newton—he’s the one, Billy, who ran down Giant Gravity—had a ring set with a lode-stone that could lift two hundred and fifty times its own weight.”
“And I know,” said Mr. Prescott, “that I am very grateful to Dr. Crandon for telling me about the new electro-magnet that I now have at the mill. I feel very much easier, now, about my workmen’s eyes.”
“Do you mean,” asked Billy, “that thing that you brought home that I thought was a new desk telephone?”
“It does resemble a telephone,” said Dr. Crandon, “only it has a tip instead of a mouthpiece. It’s a great thing for taking bits of steel out of eyes.”
“Isn’t there such a thing,” asked John Bradford, “as a magnetic separator?”
“Glad to hear from you once more, Bradford,” said Mr. Prescott, with a smile. “It has been some time since you have said anything.”
“I have been having too good a time,” said John Bradford, “to want to talk. I should like, now, to have you tell us about the separator.”
“It is an electro-magnetic drum. When the finely crushed ore is poured on it in a stream, the drum attracts the iron, while the earthy matter, which is non-magnetic, falls off by the action of gravity. The iron is carried on by the drum, until a brush arrangement sweeps it off into a truck.
“That is a case, Billy, where Giant Gravity and Giant Electro-magnet fight over the ore, and each gets away with a part of it.
“Perhaps I ought to explain to you that, when a bar of soft iron is put inside an insulated coil of copper wire and a current of electricity is passed through it, it becomes a powerful magnet. That is what we mean by an electro-magnet. The advantage of that is that it ceases to be a magnet when the current ceases, so it can be controlled. You will see some before I am through showing you giants.