A COMPOUND FLUID. Ill
which water runs, mixes with it and changes its colour."
"Many substances,"said his father, " were once thought to be simple, which the knowledge of chemistry has since taught us are formed by the union of other bodies, very opposite in their natures—water is one of these : you will understand more of its properties, I hope, when we have time to study chemistry together. But now I will only tell you, that water is composed of two airs or gases; one of them is lighter than any substance we are acquainted with; it is very inflammable, and burns when flame is applied to it; the other is that part of the atmosphere which is absolutely necessary to the existence of living creatures,