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than of time in the abstract. These divisions of time respect two things, — first, duration, e. g., a year, a month, a day, &c., and second, succession, e. g., the year 1842 is the 66th in the order of succession from the declaration of independence of these United States. A given period of time however, is only determinable by affixing a definite length to the year, month, week, day, &c. And for this we are dependent, partly on our internal perceptions of time, as produced by the regular and uniform motions of certain external objects, but principally on the motions of the objects themselves; e. g., the motions of those two great celestial bodies, the sun and the moon. These, by their regular and uninterrupted movements from age to age, have induced such astronomical observations of their respective revolutions even from early antiquity, as finally to ultimate in the establishment of accurate and unalterable measurements of the duration of time; the revolutions of the sun, determining the length of the year, and those of the moon, the month, and day. Then also, as these only answer the purposes of measuring time by its larger divisions, for the conveniences of social life, the smaller divisions of hours, minutes, seconds, &c., have been adopted. Hence we denominate the larger divisions of time the natural, and the smaller, the social. It is also well to observe, that natural divisions of time are only determinable by astronomical science; while its other divisions (e. g., those established by law and custom) lay exclusively within the province of history, and which we call, its civil divisions. Still, the astronomical divisions of

natural time cannot determine the length of any given period, separate from its connexion with its civil or historical divisions. Hence, their inseparable dependance, the one on the other.

Astronomy, as a science, has finally attained to such a degree of perfection, as not only to supply the deficiences of that vagueness which attends the measurement of time by the seasons, but to determine that the precise length of each solar year is three hundred and sixty-five days, five hours, forty-eight minutes, fortyfive seconds and thirty thirds. In historical Chronology, however, the more minute parts of the year as above are omitted, till the portions amount to twenty-four hours, or an intercalary day; at the recurrence of which, it adds to the then present year one more day, making it three hundred and sixty-six. Hence the distinction between the intercalary or leap year, and the common year. Astronomers also institute a distinction between the tropical and sideral solar year; the former of which is described by the motions of the sun between the tropics, and the latter, the time it requires to reach the same star, (the fixed stars, during the tropical revolution of the sun having had a motion. of their own,) at which it was observed at the beginning of its revolution. But as the difference between the two years amounts only to twenty minutes, twentyfive seconds, and thirty thirds, it does not affect the periods of time in general Chronology. As to the point at which the natural year begins, there is no agreement among different nations, some commencing it in the spring, and others in summer.

The solar year, being divided into twelve equal parts, constitutes the twelve solar months, which is the time required by the sun to pass through the twelve signs of the Zodiac, making each month to consist of thirty days, ten hours, twenty-nine minutes, forty-seven seconds and thirty thirds.

The Lunar year consists of the twelve revolutions of the moon, each from one new moon to another, which constitute the Lunar months; and these twelve revolutions being again divided into four parts, are the four changes in the phases of the moon during its revolution through the signs of the Ecliptic; and are called the new moon, the first quarter, the full moon, and the

last quarter. The lunar month astronomically amounts to twenty-nine days, twelve hours, fourty-four minutes, three seconds and twelve thirds; and the year to three hundred and fifty-four days, eight hours, fortyeight minutes, thirty-eight seconds and twelve thirds. The excess of length of the solar over the lunar year therefore is, ten days, twenty-one hours, no minutes, seven seconds, eighteen thirds.

This year, adopted by the Arabians, forms the meas urement of time of the Mohammedan Era. The excess of its fractions, when they amounted to a day, upon the improvement of Arabian astronomical science, was made intercalary; eleven of which was annexed to a cycle of thirty years, which cycle contained eleven leap years of three hundred and fifty-five days; which leap years are, the second, fifth, seventh, tenth, thirteenth, fifteenth, eighteenth, twenty-first, twenty-fourth, twenty-sixth, and twenty-ninth. The

excess of the ten days, twenty-one hours, &c., of the solar over the lunar year, makes thirty-two of the former, equal to thirty-three years and four or five days of the latter. Indeed, according to Prideaux, the Arabs, from the time of Mohamet, have used a year purely lunar, and the Turks do the same in imitation of them.1

We assume, then, that the solar year (minus the fractions, which do not enter into the historical calculations of time) of three hundred and sixty-five days, is the standard of measurement for all chronological deductions in the department of PROFANE history. Still, it may not be uninteresting to an inquiring mind to spread before him a brief outline of the progressive developements of astronomical science, which has resulted in furnishing at our hands, so accurate a criterion for the determination of chronological epochs.

But before entering upon this subject it will, perhaps, be well to furnish the following conjecture as to the probable length of the ante-diluvian year, from the pen of the learned Shuckford. He observes,

"It is something difficult to say, of what length the year was, which was in use in the early ages. Before the Flood, it is most probable that the civil and solar year were the same, and that three hundred and sixty days were the exact measure of both. In that space of time the Sun made one entire revolution: it was easy and natural for the first astronomers to divide the circle of the Sun's annual course into three hundred and

1. Prideaux. vol. ii. p. 42.

sixty parts, long before geometry arrived at perfection enough to afford a reason for choosing to divide circles into that number of degrees. All the time of the antidiluvian world, chronology was fixed and easy, for a year could be more exactly measured than it now can. "At the Flood the Heavens underwent some change; the motion of the Sun was altered, and a year, or annual revolution of it became, as it now is, five days and almost six hours longer than it was before. That such a change had been made, 1 most of the philosophers observed, and, without doubt, as soon as they did observe it, they endeavored to set right their chronology by it: for it is evident, that as soon as the solar year became thus augmented, the ancient measure of a year would not do, but mistakes must creep in, and grow more and more every year they continued to compute by it." 2

But, the best endeavors of these early philosophers to this end were extremely defective, as may be inferred from the following brief, but accurate summary of Dr. Hally, respecting the state of astronomical science in these remote ages. He says,

"The astronomy of the ancients is usually reckoned for one of those sciences, wherein the learning of the Egyptians consisted; and Strabo expressly declares, that there were several universities in Babylon wherein astronomy was chiefly professed; and Pliny tells us

1. See Plutarch de Placit. Philos. lib. ii., c. 8, lib. iii., c. 12, lib. v., c. 18; and Plato Polit. p. 174, 175, 269, 270, 271; and Laertius in vit. Anaxagor, lib. ix., seg. 33. 2. Vol. i., p. 8.

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