Q. Why is the draught of a short flue more slack that that of a long one?
A. For many reasons. 1st—The fire is always dull and sluggish if the chimney be too short.
2ndly—The smoke rolls out of the chimney, before it has acquired its full velocity.
3rdly—The wind, rain, and air, have more influence over a short funnel, than over a long one.
Q. Why is the fire always dull and sluggish if the chimney-flue be very short?
A. Because the draught is so bad: and as the rarefied air passes up the chimney very tardily, fresh air flows as tardily towards the fire, to supply it with oxygen.
Q. On what does the intensity of fire depend?
A. The intensity of fire is always in proportion to the quantity of oxygen with which it is supplied.
Q. Why does not smoke acquire its full velocity in a short funnel?