287. Why does poking a fire cause it to burn more brightly?
Because it opens avenues through which the air may enter to supply oxygen.
288. Why do "blowers" improve the draft of air through a fire?
Because, by obstructing the passage of the current of air over the fire, they cause additional air to pass through it, and therefore a greater amount of oxygen is carried to the coals.
Unconsumed particles of coal, rendered volatile by heat, and driven off.
Carbon in minute particles, driven off with other volatile matters and deposited on the walls of chimneys.
291. Why do fresh coals increase the quantity of smoke?
Because they contain volatile matters which are easily driven off; and because, also, they reduce momentarily the heat, so that those matters that first escape cannot be consumed.