Rensselaer Union, Volume 7, Number 35, Rensselaer, Jasper County, 20 May 1875 — The New Standard Clock at Greenwich. [ARTICLE]

The New Standard Clock at Greenwich.

The new standard sidereal clock at the observatory, Greenwich, planned by the Astronomer Royal, is pronounced a great success and is probably the best clock in the world. Nature contains a long account of its mechanism and especially of its pendulum, which is of a most ingenious and complex character. The article concludes with a brief account of the use made of the clock: “It has been mentioned that the clock completes a galvanic circuit fifty-nine times in each minute but omits the sixtieth contact. The currents thus obtained (a small battery only being used on the clock) are used to work a relay from which three independent currents from other batteries are derived. One acts upon the seconds magnet of the chronograph for impress of seconds punctures on the paper on the revolving cylinder. The omission of one second in each minute marks with certainty the commencement of the minute. Observations at all the fundamental instruments are registered on this cylinder, and comparisons of clocks are thus entirely avoided. Another current regulates a half-seconds chronometer on the eyte-end of the great equatorial. The third current regulates the pendulum of a half-seconds clock in the great equatorial room, drives a tapper to make audible the seconds of the clock, and drives also a galvanic chronometer placed in the computing-room for use in the daily work jof comparing and setting to time the mean solar* standard clock. The omission of one current in each minute is unimportant as concerns the regulated chronometer and clock, but not so as regards the chronometer which is driven by the current. To accommodate the chronometer to this state of things its second wheel is cut with fifty-nine teeth only, and its seconds circle on the dial correspondingly divided into fifty-nine equal parts. The resting of the hand during one second, which takes place at a particular division of the dial, consequent on the loss of one current in each minute, is therefore compensated for by this construction of the seconds wheel and engraved dial-plate.”