A. 1st—When the hydrogen of the tallow and oxygen of the air condense into water, a vacuum is made; and the air is disturbed, as a pond would be, if a pail of water were taken out.
2ndly—When the carbon of tallow and oxygen of the air expand into carbonic acid gas, the air is again disturbed; in a similar way as by the explosion of gunpowder.
Q. Why does the flame of a candle produce light?
A. The chemical changes made by combustion, excite undulations of ether, which (striking the eye) produce light. (see p. [46].)
Q. Why is the flame of a candle yellow?
A. Only the outer coat of the flame is yellow; the lower part of the flame is violet; and the inside of the flame is hollow.
Q. Why is the outside of the flame yellow?
A. Because the carbon of the tallow (being in a state of perfect combustion) is made white-hot.
Q. Why is the bottom part purple of the flame of a candle?