Before we can accept this explanation we must be quite satisfied that Fire is a substance.
Wherever we perceive light and heat emanating simultaneously from a combustible body, we say—there is fire—but we can bring forward no proof of the material existence of this so-called element. We cannot weigh it, measure it, or put it in a bottle; nor can we imagine it existing apart from a burning substance. Fire, after all, may be nothing but a name for certain phenomena of heat and light. These two great forces are intimately connected; thus, whenever we raise a solid object to a high temperature it becomes luminous; first it emits a dull red light, which changes as the temperature increases to orange, then to yellow, and finally to full white.
The flame of a candle is a white hot cone of volatile matter, which we vaguely term Fire—if we can discover the real nature of this cone we shall be able to define Fire with some degree of accuracy.
The chemist tells us that nothing can be absolutely destroyed, and that what we call destruction is merely the conversion of a visible body into an invisible one. To reconcile this statement with the gradual disappearance of the burning candle, we are forced to conclude that the tallow is changed into an invisible gas or vapour, and escapes into the air. Now as no solid can become aëriform without the agency of heat, the question naturally arises—whence comes the heat that vaporizes the tallow?
