which is red, and sulphur, which is yellow. Sulphur has little or no odor, and hydrogen has none, but when united they form a gas which has the odor of spoiled eggs. White sugar is nothing but black charcoal and water. It will thus be seen that here is a source of _new_ things in nature. Whatever chemical affinity touches is changed. And so we have found another force in our drop of water taken from the goblet, more wonderful than any yet named, a mighty, transforming energy which has but one worthy rival in the work of creating new things, the vital principle, and even that must yield at last to this all conquering power. If our goblet was large, and held a pound of water, (about a pint,) we should find that to pull the molecules apart, that is, make it into steam, would require a force which would raise four tons to the height of one hundred feet. But more wonderful still, to separate the pound of water into two chemical constituents would require, according to Prof. Cooke, an energy which would raise 5,314,200 pounds one foot. Our pint of water would then occupy 1800 times its present volume. Let us now give a striking and beautiful illustration of chemical affinity. We will throw into this tumbler a piece of potassium (symbol K) half as large as a pea. This interesting metal was discovered by Davy in 1807. Its affinity for O is very great. As soon as it falls upon the water it abstracts oxygen and forms potassium oxide (potash), while the hydrogen and a small amount of volatilized K escape and are burned with a brilliant violet flame, on account of the heat evolved by the energetic chemical action. [Illustration: POTASSIUM BURNING BY COMBINING WITH THE OXYGEN OF WATER.] IMPORTANT DATES. The composition of water was discovered about one hundred years ago. Cavendish found hydrogen in 1776, and Priestly discovered oxygen in 1774, August 1st, a date which some one says “may almost be accepted as the birthday of modern chemistry.” Is it not remarkable that four of the brightest “red letter days” in the history of this science should be embraced within two decades, from 1754 to 1774? In 1754 Joseph Black discovered carbonic acid gas; in 1766 Dr. Cavendish found hydrogen; in 1772 Dr. Rutherford discovered nitrogen, and in 1774 Dr. Priestly found the King of the Elements, oxygen. Until then mankind were ignorant of the existence of a substance which composes in the aggregate one half the earth. ANALYSIS OF WATER.