CHAPTER IV.
SMOKE.
Q. Why does smoke ascend the chimney?
A. As the air of the room passes over the fire, it becomes heated; and (being thus made lighter,) ascends the chimney, carrying the smoke with it.
Q. What is smoke?
A. Small particles of carbon, separated by combustion from the fuel, but not consumed.
Q. Why do smoke and steam curl, as they ascend?
A. Because they are moved in a right line, and then pushed on all sides; and this forces them into a circular motion.
Q. What are blacks?