Page:Collier's New Encyclopedia v. 05.djvu/81

LEFT HOROLOGY 57 HOROSCOPE 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 i*egulator, 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, ©r 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 standai'd clock at some - ^ -TlBBROSITY c/ ^ - • ISCHIUM Tf?CClAHT£/i •^Cf^i-cetiBut^ iAtf6C fAiTSffKI S/^filLPA5r£lff COFFIf BON£ 7^ SKELETON OF HORSE ©f 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 lor pocket timepieces and those which cannot be kept in a fixed position, as on shipboard. The train of wheelwork is ehiefly 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 hea'y 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. HOROSCOPE, in astrology, an ob- servation of the sky and the configura- tion of the planets at a certain moment as at the instant of a person's birth, from which the astrologer claimed to be able to foretell the future. Also a