Pour some spirit of wine into a watch-glass, and inflame it; place a
straw across this flame, and it will only be ignited and charred at the
outer edge; the middle of the straw will be uninjured, for there is no
ignited matter in the centre of the flame. Or if you hold a card over a
candle-flame where it will be singed you will find a browning ring and
not a solid scorch.