Do not be disturbed by these cabalistic symbols; they are simply the chemist’s name for water; a most expressive name, too, as we shall presently discover. Some names are misnomers. Abel Blackman may be both weak and a white man. Our letters can not mislead. They abbreviate, show the class of each substance, the elements that form it, and their proportions. Berzelius devised this mode of naming. (Who was Berzelius?) On the table stands a glass of water. How beautiful it is! Even diamonds, costliest of gems, are valued in proportion as they possess its marvelous clearness, those of the “first water” being most highly prized. We are now to speak of some of the _chemical_ properties of water; hereafter we shall consider the physical characteristics. DISTINCTION BETWEEN ATOMS AND MOLECULES. See! I have dipped my pencil into the goblet, and brought up a drop of water. What force binds together the pencil and the drop? What holds the drop to other drops? Why is not this ice instead of water? If I shake the pencil in what direction does the drop fall? If the drop were larger than the world, which way would the world go? What other force is there in it which, according to Faraday, is equal to that in a flash of lightning? Here are, then, five great forces in a drop of water, yet none of them changes its nature. It is still H₂O. Let us place this drop of water in the upright tube of an atomizer. Apply air. See, the drop has broken into thousands of particles. Now, suppose we could take one of these and place it in a flask. Apply heat, and we should separate the little particle into thousands of particles of steam, but each of these, and any lesser division of these, would still be H₂O. The minutest division of the water _possible_ would be called a _molecule_, yet it would still be water, and composed of two parts of hydrogen and one of oxygen. The old ocean itself contains the same. The Cracow beds of salt are made of chlorine and sodium, and the minutest dust from one of its crystals would be found to contain the same elements, and in the same proportion, both by weight and measure. Molecules, then, combined, make only _masses_ of the same nature. But molecules are composed of atoms, and whenever atoms of two or more different substances are combined they always form something different from either of these. The force that unites them is called chemical affinity, or sometimes the chemical force. For example, tenacious iron unites with a gas and forms a brittle, red substance, rust. Chlorine is a poisonous gas, and sodium will burn on water, both deadly; united they give us salt; absolutely essential to life. Hydrogen is the best substance in the world to burn, and oxygen the best supporter of combustion. When united they form water, which is universally employed to extinguish fire. Blue vitriol is blue, as the name implies, yet it is composed of four elements, two of which, H and O, are colorless, copper,