226 



CHRONODISTICH CHRY8OBERYL. 



'ui account of wliich they are preferable, as histori- 

 cal records, to many modern works. Of course, 

 tJiey do not equal in value the result of the deep re- 

 searches of a Gibbon or a Niebuhr. Young men, in 

 search of historical knowledge, ought to apply 

 themselves more frequently to these sources, and 

 not trust so much to the writers who drew from them ; 

 and we can say, from experience, that they would 

 find them very interesting reading. (For informa- 

 tion respecting the chronicles of the middle ages, \\ c 

 would refer the reader to the treatises by Rosier, in 

 Latin, particularly the preface to his Chronica Medii 

 Evi(nQ8), and the directories ofFreher and Ade- 

 lung.) Chronicle is also often used as the title of 

 newspapers. The most important of these is the 

 (London) Morning Chronicle, an excellent paper of 

 tlit- whig party. See Neicspaper. 



CHRONODISTICH, CHRONOGRAM ; a verse 

 in which certain of the letters used signify Roman 

 numbers, and indicate the year in which the event 

 happened to which the verse relates ; e. g., reges 

 ConCeDant paCeM, where CCDCM make the num- 

 ber 1800. It is little used at present. 



CHRONOLOGY (compounded of ^nes, time, and 

 Aoy, discourse) is the art of measuring time (see 

 Time], distinguishing its several constituent parts, 

 such as centuries, years, &c., by appropriate marks 

 and characters, and adjusting these parts, in an or- 

 derly manner, to past transactions, by means of eras, 

 epochs and cycles, for the illustration of history. 

 The principal means for marking the divisions of 

 time are afforded by the motions of the heavenly 

 bodies, particularly the sun and the moon, which pro- 

 duce the natural division of time into years, months, 

 and days. The necessities of life, requiring still 

 smaller and more precise divisions of time (which can 

 be measured only by artificial means), gave rise to 

 hours, minutes, and seconds. This division of time is 

 called the artificial. Even in the natural division, 

 however, there is something arbitrary, as it depends 

 solely on the will what point in the motions of the 

 heavenly bodies sliall be taken as the point of begin- 

 ning; for example, in the annual rotation of the 

 earth, whether we shall take the longest day of sum- 

 mer or the shortest day of winter. The first law- 

 givers, therefore, fixed the civil beginning and end of 

 the month, day and year, and, at the same time also, 

 the smaller divisions of these larger portions of time. 

 From this separation of the natural and artificial or 

 civil division of time, arises a division of chronology 

 into mathematical, astronomical and historical. As- 

 tronomical chronology determines the duration of 

 the natural portions of time by the revolutions of the 

 heavenly bodies ; historical chronology treats of the 

 civil divisions of time, of the methods of reckoning 

 time among different nations, of ancient periods or 

 remarkable epochs, &c. It is obvious that each of 

 these divisions of chronology requires the assistance 

 of the others. All historical chronology is grounded 

 on the astronomical, which cannot determine the 

 duration of the periods of time without the aid of the 

 civil division. Mathematicians and astronomers de- 

 termine the natural periods of time as they are in- 

 dicated by the motions of the sun and moon. It is 

 left to legislators to determine by law on what day 

 the year shall begin, how many days shall constitute 

 a month, how many a week, &c. This civil regula- 

 tion is the foundation of the calendar (q. v.) or alma- 

 nac. Thus far must astronomical chronology be 

 connected with historical; but the latter only can 

 teach us the divisions adopted by different people. 

 Historical chronology explains, 1. the form of the 

 year among different nations, as it is regulated by 

 lawgivprs, founders of religions, and other founders 

 of civil society : 2. those events which are selected by 



different nations as eras, that is, as points from which 

 they begin their reckoning ; e. g., the Yiigs of the 

 Hindoos, the era of Nabonassar, the era of the Se- 

 leticidas, among the Chaldeans, Syrians, Persians, 

 Fgyptians; the creation of the world, among the 

 Jews; the birth of Christ, among Christiana; the 

 Olympiads, among the Greeks ; the building of Rome 

 and the consular era, among the Romans ; the He'i- 

 ra, or flight of Mohammed, among the Mohamnte- 

 dans, &c. As so many different eras render the reck- 

 oning of time difficult, it, 3dly, selects a form of the 

 year and an era to which it refers those of other 

 nations, and by which it arranges the history of all 

 nations and tinu-s. The European chronologist and 

 historian must refer the eras and years of all people 

 to those used in modern Europe. Mathematical and 

 astronomical chronology is taught in the manuals 

 of astronomy. Among these may be mentioned 

 the Astronomic of L.uande (vol. 1. p. 270, 2d 

 ed.) The Manual of Astronomical and Technical 

 Chronology (from the sources) of D.L. Ideler (vol. I. 

 Berlin, 1825, vol. 1, 1826) is an excellent work. See 

 also Hales' Analysis of Chronology ; Usher's An- 

 nals ; Blair's Chronology, and Playfair's Chronology. 

 The most complete work on the subject is the Art 

 de Verifier les Dates, by the Benedictines of St 

 Maur. 



CHRONOMETER ; a time-piece of a peculiai 

 construction, at present much employed by naviga- 

 tors in determining the longitude at sea. In general, 

 chronometers are much larger than common watches, 

 and are hung in gimbals, in boxes six or eight inches 

 square ; but there are also many pocket chronometers 

 wliich, externally, have all the appearance of the bet- 

 ter sort of pocket watches, and internally differ from 

 these only in the construction of the balance. The 

 balance and hair-spring are the principal agents in 

 regulating the rate of going in a common watch, 

 being to this what the pendulum is to a common clock ; 

 and this spring, in the former, like the pendulum in 

 the latter, is subject to expansions and contractions 

 under different degrees of heat and cold, which, of 

 course, affect the speed or rate of the machine ; and 

 the methods of correcting this inaccuracy mark the 

 difference between the watch and chronometer. 

 These are very numerous. {See Horology.) All 

 the lines of packets between the United States anil 

 Europe have chronometers. See Clockwork. 



An instrument under the name of chronometer is 

 also used by musicians for the accurate measurement 

 of tune. Two sorts have been invented for different 

 purposes. The first supplies the motion of a conduct- 

 or, and regularly beats time. In the British Maga- 

 zine (ii. 283) may be found an account of a graduated 

 pendulum for this purpose, proposed by Dr Robinson ; 

 and others have since been sold at the principal music- 

 shops in London. The second is used by tuner* 

 of instruments, to measure the velocity of beats. 

 On this point, the reader may consult doctor Smith's 

 Harmonics, p. 210, See Metronome. 



CHRYSALIS. See Papilw. 



CHRYSEIS. See Achilles. 



CHRYSIPPUS, a Stoic philosopher of Cilicia, dis- 

 tinguished for his skill in disputing. He was the 

 principal opposer of the Epicureans, and is said to 

 have written 700 different works, mostly of a dialec- 

 tical character; but of these no complete work is 

 extant. He died, at a great age, about 206 years 

 B. C. 



CHRYSOBERYL, (sometimes called cymophanc, 

 and, by the jewellers, Oriental chrysolite') was for a 

 long time, only known as -occurring in semi-transpn- 

 rcnt, rounded pieces, in the alluvial deposits of rivers, 

 along with other species of gems. '1 hus, in Brazil, 

 it was found along with the diamond <md topaz, and 



