Part 787

Ep"i*cy`cle (?), n. [L. epicyclus, Gr. &?;; 'epi` upon + &?; circle. See Cycle.] 1. (Ptolemaic Astron.) A circle, whose center moves round in the circumference of a greater circle; or a small circle, whose center, being fixed in the deferent of a planet, is carried along with the deferent, and yet, by its own peculiar motion, carries the body of the planet fastened to it round its proper center.

The schoolmen were like astronomers which did feign eccentrics, and epicycles, and such engines of orbs.

Bacon.

2. (Mech.) A circle which rolls on the circumference of another circle, either externally or internally.

Ep`i*cyc"lic (?), a. Pertaining to, resembling, or having the motion of, an epicycle.

Epicyclic train (Mach.), a train of mechanism in which epicyclic motion is involved; esp., a train of spur wheels, bevel wheels, or belt pulleys, in which an arm, carrying one or more of the wheels, sweeps around a center lying in an axis common to the other wheels.

Ep`i*cy"cloid (?), n. [Epicycle + -oid: cf. F. épicycloïde.] (Geom.) A curve traced by a point in the circumference of a circle which rolls on the convex side of a fixed circle.

Any point rigidly connected with the rolling circle, but not in its circumference, traces a curve called an epitrochoid. The curve traced by a point in the circumference of the rolling circle when it rolls on the concave side of a fixed circle is called a hypocycloid; the curve traced by a point rigidly connected with the rolling circle in this case, but not its circumference, is called a hypotrochoid. All the curves mentioned above belong to the class class called roulettes or trochoids. See Trochoid.

Ep`i*cy*cloid"al (?), a. Pertaining to the epicycloid, or having its properties.

Epicycloidal wheel, a device for producing straight-line motion from circular motion, on the principle that a pin fastened in the periphery of a gear wheel will describe a straight line when the wheel rolls around inside a fixed internal gear of twice its diameter.

Ep`i*deic"tic (?), a. [Gr. &?;, fr. &?; to show forth, display; 'epi` + &?; to show. Cf. Epidictic.] Serving to show forth, explain, or exhibit; - - applied by the Greeks to a kind of oratory, which, by full amplification, seeks to persuade.

{ Ep`i*dem"ic (?), Ep`i*dem"ic*al (?), } a. [L. epidemus, Gr. &?;, &?;, among the people, epidemic; &?; in + &?; people: cf. F. épidémique. Cf. Demagogue.] 1. (Med.) Common to, or affecting at the same time, a large number in a community; -- applied to a disease which, spreading widely, attacks many persons at the same time; as, an epidemic disease; an epidemic catarrh, fever, etc. See Endemic.

2. Spreading widely, or generally prevailing; affecting great numbers, as an epidemic does; as, epidemic rage; an epidemic evil.

It was the epidemical sin of the nation.

Bp. Burnet.

Ep`i*dem"ic (?), n. [Cf. Epidemy.] 1. (Med.) An epidemic disease.

2. Anything which takes possession of the minds of people as an epidemic does of their bodies; as, an epidemic of terror.

Ep`i*dem"ic*al*ly, adv. In an epidemic manner.

Ep`i*de`mi*og"ra*phy (?), n. [Epidemy + -graphy.] (Med.) A treatise upon, or history of, epidemic diseases.

Ep`i*de`mi*o*log"ic*al (?), a. Connected with, or pertaining to, epidemiology.

Ep`i*de`mi*ol"o*gist (?), n. A person skilled in epidemiology.

Ep`i*de`mi*ol"o*gy (?), n. [Epidemy + -logy.] (Med.) That branch of science which treats of epidemics.

Ep"i*dem`y (?), n. [Gr. &?;, fr. &?;: cf. F. épidémie. See Epidemic.] (Med.) An epidemic disease. Dunglison.

Ep"i*derm (?), n. [Cf. F. épiderme. See Epidermis.] (Anat.) The epidermis.

Ep`i*der"mal (?), a. Of or pertaining to the epidermis; epidermic; cuticular.

Ep`i*der*mat"ic (?), a. Epidermal. [R.]

Ep`i*der"ma*toid (?), a. [Gr. 'epi` upon + de`rma, -atos, skin + -oid. Cf. Epidermoid.] (Anat.) Epidermoid. Owen.

Ep`i*der"me*ous (?), a. Epidermal. [R.]