HOROLOGY, that branch of science which treats of the principles and con struction of machines for measuring and indicating portions of time. It is al most an impossibility to state who was the individual that intended either a clock or a watch; due to the fact that formerly the term horologium was ap plied to a sun dial or a clock indiscrimi nately. As far back as the close of the 13th or the begianing of the 14th cen tury, striking clocks were known in Italy. In 1288, as we are told by Coke, a stone clock tower was erected opposite West minster Hall, and in it was placed a clock. About 1364 a German horologer, Henry de Wick, de Vick, de Wyk, or de Wyck, set up a clock in the tower of the palace of Charles V. of France.
The date at which the size of clocks was so far reduced as to render them portable, is uncertain; it must, however, have been anterior to 1544; for in this latter year the corporation of master clockmakers at Paris procured from Francis I. a statute precluding all but master clockmakers from constructing clocks or watches, large or small.
The third era in clockwork was the application of the pendulum. Galileo was the first who remarked, or at least the first who formally announced, in his work on mechanics and motions which was published in 1639, the iso chronal property of oscillating bodies suspended by strings of the same length. In a general view, horological machines may be regarded as consisting of three essential parts: 1. A moving power, which produces a rotary motion about an axle; 2. A train of wheelwork, by means of which a velocity is obtained having any required ratio to that of the pri mary axle; 3. A regulator, by which the rapidity of the revolution is determined, and uniformity of motion produced. The moving power is either a heavy weight, which descends by the force of gravity, or a spring which is coiled up within a barrel and unwinds itself by the force by which the original rotatory motion is converted into a reciprocating motion, and gives impetus to the pendulum or balance. Some other parts are also of
primary importance, as the maintaining power, a contrivance by means of which the motion is maintained or the machine kept going while the weight or spring is being wound up; the fusee by which in watches and spring clocks the force acting on the wheel work is rendered equal in all states of the tension of the spring.
Electrical clocks are of two kinds— electrical dials and electrical clocks. The electrical dial has no body belong ing to it, but is connected by means of a wire with a standard clock at some of its elasticity; the first is preferred on account of the perfect regularity of its action when the instrument is to remain fixed in a place; the second is necessary for pocket timepieces and those which cannot be kept in a fixed position, as on shipboard. The train of wheelwork is chiefly remarkable on account of the delicacy and accuracy of its construc tion. The regulator is either a pendu lum, of which, by the theory of falling bodies, the oscillations are isochronal or performed in equal terms; or a heavy balance, the reciprocal vibrations of which are also isochronal. Of the vari ous mechanical contrivances introduced into horological machines for accomplish ing particular purposes, the most im portant is the escapement (or scape ment), or that part of the mechanism other place. An apparatus is also pro vided for sending a galvanic current through the wire at certain regular in tervals of time. By this means the dial hands are made to leap over a small portion of their compass whenever a cur rent is transmitted through the wire; and the time value of the movement is marked by the figures on the dial. An electric clock, however, is one that car ries with it its sources of power and is independent of any wire connected with another place.