“I thought a chimney was only to let the smoke up,” said Rollo.
“No,” replied his father, “that is not all, by any means. If a fire made no smoke, it would still be almost as necessary as it is now to have a chimney. In fact, some fires do not make any smoke; some kinds of coal, dug out of the ground, do not make any smoke, and charcoal fires do not make any smoke; but still it is always necessary in such cases to have chimneys.
“Because,” he continued, “you must understand, that air gets changed in passing through a fire, so that it will not answer afterwards either to breathe, or to make a fire burn again; and therefore there must be some way for it to escape, not only out of the way of the fire, but also out of the room where people want to live and breathe. There is always such a stream of air rising up from every fire, great or small, even from a lamp.”
“Why, father, is a lamp a fire?” said Rollo.
“Certainly,” said his father, “it is a small fire made by burning oil on the top of a wick, and the hot air rises in a constant stream above it. So in a room, if there was no chimney over the fire, all the air that had passed through the fire, and become heated, would ascend to the top of the room. I saw the proof of this once, in a very singular manner.”
“How was it, sir?” said Rollo.
“It was one day when I was travelling. It was in the winter. I came to a hotel and was going up stairs to my room just before dinner. When I got to the head of the stairs, and was about going along the passage-way to my room, I saw, a little way before me, a door open, which led into another room; and there was a thick stream of white smoke, pouring out in the most beautiful manner, at the upper part of the door, and falling up to the ceiling.”
“Falling up!” said Rollo.
“Yes,” said his father. “It looked precisely like a little waterfall, falling up. There was no smoke at all coming out, except close to the top of the door; and, as soon as it got out, it went up to the ceiling of the entry, and from that it spread all around like water. It was very beautiful, but I had not time to stop to admire it, for I presumed that the room was on fire.”
“And did you cry fire?” said Rollo.