Part 11

Electricity. A peculiar condition of the molecules of a body or of the ether surrounding the molecules, or else a sort of fluid or other matter in the form of small bodies called electrons. It is easier to tell what electricity does or how it is produced than to define it, especially since physicists have not been able to agree about its precise nature.

Electrode. Either pole of a cell.

Electrolysis. The decomposition of a compound by means of an electric current.

Electrolyte. A substance which, in solution, can carry an electric current to an appreciable extent.

Electron. The electric charge of an atom. A very small particle which is electrically charged. The size of the electron has been variously calculated, and some physicists declare that the negative electron has only 1/1700 the mass of a hydrogen atom.

Element. One of a number of substances formerly considered to be indivisible. An electric cell.

Emanation. A gaseous substance produced by a radioactive material.

Embryo. The offspring of an animal before birth or emergence from the egg. The scientific study of the embryo is called embryology.

Endogenous. Growing from within.

Endosperm. The nutritive tissue enclosed with the embryo in seeds.

Endothelium. The layer of cells lining blood vessels, the interior of the heart, etc.

Energy. Ability to do work or change the nature of bodies. Heat and light are considered forms of energy.

Entomology. The study of insects.

Environment. Surrounding conditions, influences, and powers of all sorts. Everything which, directly or indirectly, affects the fate of an organism forms part of its environment.

Eocene. Relating to the lowest division of the Tertiary strata.

Epiphyte. A plant which grows upon another but which is not fed by it. A vegetable parasite on an animal body.

Equation. A compensation for inaccuracy. In mathematics, a formula affirming the equivalence of two expressions. An expression in symbols of a chemical reaction.

Equinox. The time when the sun crosses the equator, and day and night are of equal length.

Erbium. A metallic element. Symbol: Er.

Erg. The work done by a force that, when it acts for one second on mass of one gram, produces a velocity of one centimeter per second.

Erosion. Gradual destruction or wearing away, as of land by water.

Esthetics. Also spelled: æsthetics. The study of beauty. It is, at present, rather an art or a branch of philosophy than an exact science.

Ether. An anesthetic liquid. Totally distinct is this meaning: the medium through which light-waves pass, which is supposed to have a density infinitely less than that of the lightest gas. The nature of the ether is in dispute.

Ethics. The branch of philosophy concerned with human conduct. It may at some future time rank as a science.

Ethnology. The science dealing with the races of mankind. It has not, alas, always been thoroughly scientific.

Ethyl alcohol. The alcohol which cheers and also inebriates men. Before Prohibition, practically the only kind of alcohol which people drank.

Europium. A metallic element. Symbol: Eu.

Evaporate. Change (usually with no great rapidity) from the liquid to the gaseous state.