Epicycloid—A curve generated by any point in the circumference of a circle as it rolls on the outside of the circumference of a fixed circle. This curve is the best for the face of the teeth of a driving wheel.
Equation Clocks—An obsolete form of clock which showed true solar or sun-dial time instead of mean solar, or average time.
Equation of Time—The difference between true time and mean, or averaged time. There are four days in the Gregorian year when the true time and mean time agree, and the equation of time is zero: These are December 24, April 15, June 15, and August 31. Between the first two dates and the last two dates, true time is earlier than mean time; for the other two periods of the year it is later.
Escape Cock—The bracket which supports the upper ends of the escape wheel and pallet staff arbors.
Escapement—The device in a watch or clock which regulates the motion of the train thus distributing the power of the main-spring. It communicates the motive power to the balance or pendulum. Escapements are of three classes: recoil, dead, or dead-beat; and detached.
Escapement, Anchor—The recoil escapement, invented by Hooke, used in most house clocks. A name also applied to one kind of Lever Escapement with an unusually wide impulse pin. The recoil escapement is one in which each tooth of the escape wheel, after it comes to rest, is moved backward by the pallets. Altho one of the easiest escapements to set out correctly the pallets are often improperly formed making an escapement which gives indifferent service. As a timekeeper the anchor escapement is inferior to the dead-beat escapement.
