but it is now surely and systematically done. The stages of horological science are some of them remote, but they are well worth studying. The earliest divisions of time were doubtless those made by the operations of Nature, producing day and night,—the sun and moon were the earliest chronometers, and, marked by them, 'the evening and the morning were the first day.' It is even now by noting the recurrence of certain celestial phenomena that we are enabled to certify to ourselves the accuracy of our time-pieces, but although the motion of the heavenly bodies is the standard of computation for lengthened periods, it is found more convenient to reckon short terms, such as seconds, minutes, and hours, by machinery set in motion by a spring or by weights mathematically adjusted, and this in a word has given birth to the science called Horology.

We can readily comprehend the division of time into days and nights, for these, as we have said, are the natural divisions. Let us trace the origin of more arbitrary periods, such as hours, and weeks, and months, and years. First, then, as to days, let it be remembered that the beginning and ending of an ordinary English day differs in several respects from those of other nations. The Jews reckon their day, as do also the Greeks and Italians, from sunset to sunset; the Persians from sunrise to sunrise. The astronomical and nautical day is computed from noon to noon, and is reckoned by 24 hours, not by twice 12,—as, for instance, instead of writing half-past four in the morning of, we will say, Jan. 2, the astronomer would write Jan. 1. 16 h. 30 m. Our ordinary English day is reckoned from 12 to 12 at midnight, after the fashion set by Ptolemy, which has this advantage over the method of reckoning from sunrise or sunset, that the latter periods are continually varying with the seasons of the year. The grouping of seven days into a week is shown in Genesis, but the seventh day is there alone specially named. The Sabbath is still kept by the Jews on the seventh day, but Christians keep the first day of the week in honour of Christ's resurrection, and call it the Lord's Day. After the older planetary method, Sunday was named in honour of the Sun, Monday of the Moon, Tuesday of Tuesco, or Mars, Wednesday of Woden or Mercury, Thursday of Thor, Friday of Friga, Venus, Saturday of Saturn. The Month, named after the Moon in consequence of a month being nearly equal to the time occupied by the Moon in going through all her changes, is again classed under the names lunar or calendar; the lunar month is rather more than 29½ days, but as the solar month is nearly a day longer it would require more than twelve lunar months to make a year, arbitrary additions have been therefore made to each month, some consisting of 30, some of 31 days; and months so arranged to form the calendar are called calendar months, twelve of which make a year of about 365¼ days. Until the time of Julius Cæsar the year was reckoned as of 365 days only, a number which after many centuries required the addition of ninety days to rectify, he therefore ordered one of the years to consist of 444 days, and that subsequently every fourth year should contain 366 days. Even this very summary imperial method was attended with its drawbacks and difficulties, for the earth's revolution round the Sun is made in eleven minutes eleven seconds, less than 365¼ days, which minutes in the course of about 1600 years required to be taken into consideration, and in 1582 Pope Gregory XIII. took off ten days by making the 5th of October the 15th; but the Gregorian time was not introduced into England till 1752 when the error amounted to about eleven, so eleven days were subtracted from 1752 leaving it only 354 days,—much to the indignation of the illiterate people of that time, who clamoured, assembled in great mobs to testify to their sense of the great injury inflicted upon them, 'Give us back our Eleven days,'—one of Hogarth's prints of the 'Election' exhibits a paper containing this very inscription. The fury of the populace at being robbed of its precious time availed not; the day after the 2nd of September, 1752, was made the 14th of September, and from that time dated the New Style, since which the year has been almost exactly correct. Up to 1752 the legal year began in England on the 25th of March, and it was usual up to that day to employ two dates, as 1750-1; but since the change of style the year has commenced with the first of January,—nearly midwinter. As there is one day more than fifty-two weeks in a year every year begins one day later in the week than the preceding year; and after leap-year two days later. The only country in Europe which still retains the Old Style is Russia,— the difference between the styles, now twelve days, is usually indicated by O.S. and N.S., or as in one or two of our watch illustrations by 'Russian' and 'Gregorian.' As regards the smaller divisions of time, it should be noted that the minute and the hour are thus reckoned,—the Earth divided into 360 degrees, turning upon its axis once every twenty-four hours, brings fifteen degrees under the sun each hour, and makes those fifteen degrees of longitude equivalent to one hour of time,—fifteen geographical miles being equivalent to one minute of time.

The earliest horologe or hour measurer of which history makes mention is that called the Polos, and the Gnomon. Herodotus (lib. II.) ascribes their invention to the Babylonians, but Phavorinus claims it for Anaximander, and Pliny for Anaximenes. The Gnomon, which was the more simple and probably the more ancient instrument, consisted simply of a staff or pillar fixed perpendicularly in a sunny place, the shadow of which was measured by feet upon the place where it fell,—the flight of time being computed thereby. In later times the word Gnomon was the title of the sun-dial, and it is the name still in use for the style or finger which throws the shadow on the dial and thus indicates the hour. The Polos or Heliotropion was no doubt a superior instrument to the earliest Gnomon, but, from its being so seldom mentioned, we may suppose it not to have been so generally used. The Polos consisted of a basin, in the middle of which the perpendicular staff or finger was erected, and marked by lines the twelve portions of the day. The Dial was but another form of Polos; its name indicates a Roman origin,—namely, from Dies, a day, but there was a Greek sun-dial called Sciathericum, from skia, a shadow. The invention is said to have been derived by the Jews from the Babylonians, to whom, as we have seen, Herodotus ascribed it, and there is mention made in the viii. of Isaiah of the dial of Ahaz,—a king who began to reign 741 B.C. The form of the Dial of Ahaz has not been ascertained; but there is reason to believe that the ancient Jews and the Brahmins were acquainted with the uses of the dial and applied it to astronomical purposes. Dials were, it is said, not known in Rome before 293 B.C., when one was set up by Papirius Cursor the Roman General, near the Temple of Quirinus. At Athens there is an octagonal temple of the Winds still standing, which shows on each side the lines of a vertical dial and the centres where the Gnomons were placed. At one time the art of Dialling was most assiduously studied; its rudiments may be described as follows:

The plane of every dial represents the plane of some great circle on the earth, and the Gnomon the earth's axis; the vertex of a right Gnomon, the centre of the earth or visible heavens. The earth itself, compared with its distance from