It imparts heat, which has the effect of expanding both fluids and solids.
It cannot exist without the presence of combustible materials.
It has a tendency to diffuse itself in every direction.
It cannot exist without oxygen or atmospheric air.
84. What elements take part in the maintenance of a fire?
Hydrogen, carbon, and oxygen. Hydrogen and carbon exist in the fuel, and oxygen is supplied by the air.
85. How does the combustion of a fire begin?
A match made of phosphorous and sulphur (highly inflammable substances) is drawn over a piece of sand-paper; the friction of the match induces the presence of caloric, which developes heat, and ignites the match, the burning of which is sustained by the oxygen of the air. The flame is then applied to paper or wood, and the heat of the flame is sufficient to drive out hydrogen gas, which unites with the oxygen of the air, and burns, imparting greater heat to the carbon of the coals, which assumes the form of carbonic acid gas by union with oxygen, and in a little while all the conditions of combustion are established.
86. What are the properties of heat?
It may exist without fire or light.