There is no doubt that modern science contributes an ample share to making life easier. Very many indeed are the inventions and scientific discoveries that find practical applications in our daily lives. Add to this that these applications have entered into the very core of our lives, to the point where they are no longer luxuries but have become necessities demanded by the pattern on which we live. Electricity and its applications — radio, telephone, and telegraph — have all become an inseparable part of our civilization. Yet many of us enjoy these inventions and discoveries and use them daily without ever having acquainted themselves with the theoretical scientific principles that made the existence of these practical applications possible. In my view, the person who knows how the electric lamp gives light, for example, enjoys it the more and trusts it the more; for the more a man satisfies his scientific curiosity, the better he understands the scientific side of modern civilization, and the more he appreciates the services that science renders toward increasing man's prosperity.
In this article I shall try to set forth for the honored readers some of the fundamental principles on which electricity rests, because electricity constitutes the greatest motive power in the modern world, and because acquaintance with its principles opens the way to understanding many of its practical applications. But we must first cast a glance at the structure of matter before beginning our inquiry into electricity.
What is matter composed of?
We know that matter is made up of molecules, and these in turn are made up of atoms. Molecules and atoms differ as matter differs: the molecules of water, for example, are composed of the two elements oxygen and hydrogen, while the molecules of petroleum are composed of the two elements carbon and hydrogen. Yet however much the molecules or atoms of matter may differ, they all resemble one another in their construction; for all atoms, whatever their kind, their source, and the matter to which they belong, are built up of similar electrical units. Just as a man can build several houses of different appearance and shape from a single kind of stone, so nature builds the different elements from these similar electrical units. And just as the difference between the houses referred to is a difference in the arrangement of the stones, according to the architectural form to be brought out — not a difference in the unit of building, which is the stone — so the difference between the elements iron and copper, for example, is a difference in the arrangement of these electrical units, an arrangement that gives iron properties and characteristics distinguishing it from the properties and characteristics of copper.
The arrangement of the electrical units in the atom:
These electrical units, then, are the foundation on which matter
is built. They are either negative, and are called electrons, or positive, and are called protons. These units are exceedingly small in size; no microscope can show them to us. A single gram of matter contains millions of millions of these infinitesimally minute electrical units. And though they cannot be seen, modern science possesses various means of proving conclusively that they exist. The protons, or positive units, are larger in size and heavier than the electrons, or negative units: the weight of a single proton equals the weight of 1,845 electrons. And this great difference in weight results from the electrons being more active and more mobile than the protons.
These electrical units, the electrons and protons, join together in building the atoms of matter. The atom, then, is nothing but an organized group of these negative and positive units, which are always present in equal quantities; the number of electrons neither exceeds the number of protons nor falls short of it. The atom consists of a nucleus containing all the protons together with some of the electrons, gathered into a dense, compact mass around which the remaining electrons revolve. We may liken the nucleus to the sun, with the electrons revolving around it as the planets revolve around the sun. Whenever the number of these units differs, the kind of element, or of the matter to which they belong, differs. The oxygen atom, for example, contains sixteen electrons and sixteen protons, while the iron atom is composed of fifty-six electrons and fifty-six protons; the gold atom of one hundred and ninety-seven electrons and as many protons; and the radium atom of two hundred and twenty-six electrons and as many protons. The difference, then, is at bottom a difference of number. Everything we call "matter" is