"This is a trunk key.
See if the magnet pulls it."
"No-o," said Charlie, thoughtfully, "it doesn't; but it pulled all the
rest of the trunk keys I could find."
"Try this key to my office door."
Charlie tried it, and to his great amazement the key stuck fast to the
magnet.
"Surely," said I, "it pulls some door keys, and fails to pull some trunk
keys."
Charlie was more puzzled than ever. He looked at the keys, thought a
moment, then picked up my trunk key, and said: "This key is brass; the
rest are iron."
"That's so," I said.
"And all these door keys that the magnet didn't pull," he continued,
"are brass, too. Perhaps it can't pull brass things."
"Suppose you try. But first see if there are any brass things that the
magnet pulled."
Charlie looked them over. Then we tried the casters of my chair, and all
the other brass things we could find, none of which the magnet would
pull.
"There's no use in trying any longer," said Charlie. "It won't pull
brass."
"Then, there's another matter settled," I said. "The magnet does not
pull brass. Is there any thing else it does not pull?"
"Wood," said Charlie.
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