of the different states to elect the president and vice-president are called electors, and the electors of all the states form the electoral college. Each state chooses a number of electors equal to the number of members it sends to both houses of Congress; but no member of Congress or person holding civil office under the United States can serve as an elector. The electors are chosen on the Tuesday after the first Monday in November in every fourth year preceding the year in which the presidential term expires. They meet in their respective states on the second Monday in January, and cast their votes. They were originally intended to use their own judgment in casting their votes, but now they simply vote for the candidates nominated by the party by which they have been chosen as electors. The votes are then opened and counted by both houses of Congress, in joint session, on the second Wednesday of February. If no candidate has a majority of all the votes, the house of representatives chooses the president by ballot from the three who have the highest number of votes, each state having one vote; the vice-president is similarly chosen by the senate. See Johnson's American Politics and Andrews' Manual of the Constitution.
Electricity. The rubber handle of a fountain-pen when rubbed over the sleeve of one's woolen coat, acquires the property of attracting small bits of paper or wood; glass rubbed on silk behaves in the same way. The substance earliest discovered to have this property is amber, a fossil resin found on the shores of the Baltic Sea. The Greeks called this resin electron, and hence later (1603 A. D.) Dr. Gilbert called this phenomenon electric, and gave us our word electricity. These facts have been known ever since the time of Thales (600 B. C.); and for two thousand years following him they constituted the whole of electric science, barring some knowledge of lightning and the electric eel, which no one then imagined to have any connection with the amber phenomenon.
Bodies which have acquired the property of attracting small bits of paper are said to be electrified or to have an electric charge.
I. ELECTROSTATICS
The fundamental facts upon which the science of electrostatics (i. e., the science which deals with electric charges) is built, are as follows:
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| Electroscope made of Erlenmeyer Flask and Aluminium Foil |
1. From a large number of experiments it has been found that not only rubber or amber but any substance, on being rubbed with any other substance, becomes electrified. Even the tip of a camel's-hair brush, when touched to a table-top, shows electrification. Of course this requires some delicate means of detecting the electrification, such as a pair of gold leaves suspended on a glass support. Such an instrument is called an electroscope and is shown in fig. 1. Since electrification is produced by such slight means, we are led to think that “any two substances brought into contact become electrified.” This statement may be called the first law of electrostatics.
2. A second fundamental discovery in electrostatics was made by Stephen Gray (died 1736) in London. He found that when some bodies, such as metals, are electrified, the charge immediately leaks off unless the metal be supported upon glass, rubber, resin, etc. Those substances which lead off the charge quickly, he called conductors; those which prevent the charge from escaping, he called non-conductors or insulators. There are some substances, as gas, carbon, ordinary water, cotton-thread, which occupy an intermediate position between conductors and non-conductors. See list in any good treatise on electricity.
3. A third great discovery in electrostatics was made by Dufay (see Dufay), who found that all electrified bodies may be divided into two classes according as they attract or repel a given electrified particle—such as a pith-ball suspended by a silk thread and charged. The electrification which appears on glass when rubbed with silk Dufay called vitreous; we now call it positive. That kind of electrification which appears on sealing-wax or gutta-percha when rubbed with flannel, he called resinous; we now call it negative. Bodies charged with the same kind of electrification repel each other; bodies charged with opposite kinds of electrification attract each other.
4. Just “how much” two charged bodies attract (or repel) each other was first measured by the French physicist Coulomb (born 1736; died 1806). His answer constitutes what we may call the fourth great discovery in electricity. By means of a torsion-balance he found that two particles at a distance r from each other, and carrying charges e and e′ respectively, attract or repel one another, in air, with a force F, which is given by the following equation:
F = eeér2
Cavendish and Faraday found later that this expression had to be modified, when the medium between the two particles was other than air, so as to read
F = eeéKr2
where K is a constant which is known as the specific inductivity of the medium: for ordinary glass its numerical value is about six, for paraffine about two.
