Q. Why are some particles consumed and not others?
A. The combustion of the carbon depends upon its combining with the oxygen of the air: but as the outer surface of the flame prevents the access of air to the interior parts, therefore much of the carbon of those parts passes off in smoke.
Q. Why do lamps smoke?
A. Either because the wick is cut unevenly, or else because it is turned up too high.
Q. Why does a lamp smoke when the wick is cut unevenly?
A. 1st—Because the points of the jagged edge (being very easily separated from the wick,) load the flame with more carbon than it can consume: and
2ndly—As the heat of the flame is greatly diminished by these bits of wick, it is unable to consume even the usual quantity of smoke.
Q. Why does a lamp smoke when the wick is turned up too high?
A. Because more carbon is separated from the wick than can be consumed by the flame.