"See," said Jonas, "how quick it is stifled."
"Yes," replied Rollo, "it goes out almost directly."
"You see," said Jonas, "that the fire already in the stump consumes all the goodness of the air; and I stopped up the hole, so that no fresh air can come in."
"Why doesn't it go in at the top?" said Rollo.
"It does a little," said Jonas, "but not much, because the hollow of the stump is already full of bad air, and there is nothing to make a current. When there is an opening below, then there is a current up through."
"Yes," said Rollo, "it is just like a chimney."
"Yes," replied Jonas, "the stump is the chimney, and the hole is the fireplace."
"And the air in the stump," said Rollo, "gets hot, and so the cold air all around is heavier, and so it crowds down under it, and buoys the hot air up out of the stump. My father explained it all to Nathan and me."
Rollo then wanted to open the hole again, to see if the effect would be as he had described.
Then Jonas pulled away the turf from the hole at the bottom of the stump, and Rollo observed that the fire brightened up immediately.