HOROL'OGY (from Lat. horologium, (k. 6.,o,\G-,(ov, from evpoN6los, ltiirologos. telling the hour. from 6pa, hero, !pair N6-yos, logos, word, from Neiciv, I, win, to say). That branch of ap plied scienee that has for its object the measure ment of time. Although it is easy to look hack on a when time. according to the modern conception of it. as measured hours, and minute-. and seconds, was unknown, yet we find progress early made in the measurement of larger peril lis of trots,1 y chservations of the heavenly bodies: and although. in the later progress of astronomy, it is found that the movements of the more conspicuous heavenly bodies do not of ford accurate marks for the equable measure ment of time, they were, for practical objects, suffieient. and afforded at least a better measure of tine than any other phenomena which came under Ilse observation of mankind. Thus, time was early divided into years, necording to the motion 01 the sun among the constellations; into mnths. according to the motion of the moon relatively to the sun's place in the heavens; and 11110 by the alternate light, and darkness caused oy the rising and setting of the still. It was long. however, before any accurate measure was found for a division of the day itself. The earliest measure employed for this purpose that we can trace is the shadow of mu upright object, whieli gave a rough measure of time by the va riations in its length and position. This sug gested the invention of sum-dials. Another
meats (..i•ly adopted for the measurement of short periods of time was by the 111131111ty of ua tr r discharged by 111'0111/111g from olle vessel into ;M other. Instruments for the measurement of time on this principle were called eleosydra.
The running of line said from one into another was found to afford a still more certain measure. and hence the invention of the hour glass (q.v.). King Alfred is said to have served the lapse of time by noting the gradual shortening of a lighted candle. It is not very easy to trace to its source the history of the in vention which the modern clock owes its parentage; Ille dock. however. of which We have a complete description. and perhaps the earliest which attained any distinct superiority over the rude contrivances already mentioned, was the clock of Henry Vic (De Vick or De Wyck a t;t4rman. crested in the tower of the palace of Charles V., King of France, in 1379.
For the description of this first, in•elianieal timekeeper, and for the subsequent history of clock and watch making, see t'rocK ; WATCH; PLNDUI.l Al ; ESCAPEMENT. The history of the nee Of horology and of the mechanical art of the clir•k, wateli, and •h•ommi•ter maker arc so intermingled that they cannot lie considered sepa rately. They may, therefore, he found under these heads. See also TIME, STANDARP; TRA N. sEr 1 N sTEI•NIENT.