floor?"

17. "Yes, I remember I have, and found the air up there as warm as
mustard; and when I got down, and bent my head near the floor to pick up
something, I found it as cold as could be."

"That is ever the case; but I wish you to tell me how the cold air always
happens to settle down to the lower part of the room, while the warm air,
somehow, at the same time, gets above."

18. "Why, why, heavy things settle down, and the cold air--yes, yes,
that's it, I am sure--the cold air is heavier, and so settles down, and
crowds up the warm air."

"Very good. You then understand that cold air is heavier than the heated
air, as that iron is heavier than the water; so now we will go back to the
main question--what makes the smoke go upwards?"

19. "Oh! I see now as plain as day; the cold air settles down all round,
like the iron box, and drives up the hot air as fast as the fire heats it,
in the middle, like the water; and so the hot air carries the smoke along
up with it, just as feathers and things in a whirlwind. Well! I have found
out what makes smoke go up--is n't it curious?"

20. "Done like a philosopher!" cried Bunker. "The thing is settled. I will
grant that you are a teacher among a thousand. You can not only think
yourself, but can teach others to think; so you may call the position
yours as quick as you please."