Johnny then opened his knife, and, taking out some of the filings on the end of the blade, dropped them, or rather shook them, slowly into the flame.
"Oh, how pretty!" exclaimed Belle: "they burn something like gunpowder."
"So they actually burn up, and don't just get red-hot and fall down and cool?" said Alec.
"Oh, yes!" replied Johnny: "they burn up just like so much sawdust, only more so; for there would be some ashes left of sawdust, even though they might be invisible."
"So the filings have combined with the oxygen in the air, and gone off in gas?" said Belle.
"Yes," replied Johnny.
"I wish you would file some iron," said Sue, "because that experiment makes such pretty fireworks."
"Very well, I will, if you will go down and bring me a piece of iron from papa's tool-box."
Sue ran off, and Johnny continued,—
"I think I'll show you now how I make gas on a small scale."