Q. Why does a bluish flame sometimes flicker on the surface of hot cinders?
A. Gas from the hot coals at the bottom of the grate mixing with the carbon of the coals above, produces an inflammable gas (called carbonic oxide), which burns with a blue flame.
Q. Why is the flame of a good fire yellow?
A. Because both the hydrogen and carbon of the fuel are in a state of perfect combustion. It is the white heat of the carbon, which gives the pale yellow tinge to the flaming hydrogen.
Q. What is light?
A. Rapid undulations of a fluid called ether, striking on the eye.
Q. How does combustion make these undulations of light?
A. The atoms of matter (set in motion by heat) striking against this ether, produce undulations in it; as a stone thrown into a stream, would produce undulations in the water.
Q. How can undulations of ether produce light?
A. As sound is produced by undulations of air striking on the ear; so light is produced by undulations of ether striking on the eye.