In the first place, it is almost an utter impossibility to calculate with a fair degree of accuracy the days of the year and the movements of the sun. To the three hundred and sixty-five days there are still to be added the intercalary days, the result of the additional quarters of a day and night: hence it is, that it is found impossible to ascertain with exactness the proper periods for the appearance of the stars. To this we must add, too, a certain degree of uncertainty connected with these matters, that is universally admitted; thus, for instance, bad and wintry weather will often precede, by several days, the proper period for the advent of that season, a state of things known to the Greeks as proxeima/zein;[1] while at another time, it will last longer than usual, a state of circumstances known as e)pixeima/zein.[2] The effects, too, of the changes that take place in the seasons will sometimes be felt later, and at other times earlier, upon their reaching the face of the earth; and we not unfrequently hear the remark made, upon the return of fine weather, that the action of such and such a constellation is now completed.[3] And then, again, as all these phænomena depend upon certain stars, arranged and regulated in the vault of heaven, we find intervening, in accordance with the movements of certain stars, hailstorms and showers, themselves productive of no slight results, as we have already observed,[4] and apt to interfere with the anticipated regular recurrence of the seasons. Nor are we to suppose that these disappointments fall upon the human race only, for other animated beings, as well as ourselves, are deceived in regard to them, although endowed with even a greater degree of sagacity upon these points than we are, from the fact of their very existence depending so materially upon them. Hence it is, that we sometimes see the summer birds killed by too late or too early cold, and the winter birds by heat coming out of the usual season. It is for this reason, that Virgil[5] has recommended us to study the courses of the planets, and has particularly warned us to watch the passage of the cold star Saturn.

There are some who look upon the appearance of the butterfly as the surest sign of spring, because of the extreme delicacy of that insect. In this present year,[6] however, in which I am penning these lines, it has been remarked that the flights of butterflies have been killed three several times, by as many returns of the cold; while the foreign birds, which brought us by the sixth of the calends of February[7] every indication of an early spring, after that had to struggle against a winter of the greatest severity. In treating of these matters, we have to meet a twofold difficulty: first of all, we have to ascertain whether or not the celestial phænomena are regulated by certain laws, and then we have to seek how to reconcile those laws with apparent facts. We must, however, be more particularly careful to take into account the convexity of the earth, and the differences of situation in the localities upon the face of the globe; for hence it is, that the same constellation shows itself to different nations at different times, the result being, that its influence is by no means perceptible everywhere at the same moment. This difficulty has been considerably enhanced, too, by various authors, who, after making their observations in different localities, and indeed, in some instances, in the same locality, have yet given us varying or contradictory results.

There have been three great schools of astronomy, the Chaldæan, the Ægyptian, and the Grecian. To these has been added a fourth school, which was established by the Dictator Cæsar among ourselves, and to which was entrusted the duty of regulating the year in conformity with the sun's revolution,[8] under the auspices of Sosigenes, an astronomer of considerable learning and skill. His theory, too, upon the discovery of certain errors, has since been corrected, no intercalations having been made for twelve[9] successive years, upon its being found that the year which before had anticipated the constellations, was now beginning to fall behind them. Even Sosigenes himself, too, though more correct than his predecessors, has not hesitated to show, by his continual corrections in the three several treatises which he composed, that he still entertained great doubts on the subject. The writers, too, whose names are inserted at the beginning of this work,[10] have sufficiently revealed the fact of these discrepancies, the opinions of one being rarely found to agree with those of another. This, however, is less surprising in the case of those whose plea is the difference of the localities in which they wrote. But with reference to those who, though living in the same country, have still arrived at different results, we shall here mention one remarkable instance of discrepancy. Hesiod—for under his name, also, we have a treatise extant on the Science of the Stars[11]—has stated that the morning setting of the Vergiliæ takes place at the moment of the autumnal equinox; whereas Thales, we find, makes it the twenty-fifth day after the equinox, Anaximander the twenty-ninth, and Euctemon the forty-eighth.

As for ourselves, we shall follow the calculations made by Julius Cæsar,[12] which bear reference more particularly to Italy; though at the same time, we shall set forth the dicta of various other writers, bearing in mind that we are treating not of an individual country, but of Nature considered in her totality. In doing this, however, we shall name, not the writers themselves, for that would be too lengthy a task, but the countries in reference to which they speak. The reader must bear in mind, then, that for the sake of saving space, under the head of Attica, we include the islands of the Cyclades as well; under that of Macedonia, Magnesia and Thracia; under that of Egypt, Phœnice, Cyprus, and Cilicia; under that of Bœotia, Locris, Phocis, and the adjoining countries; under that of Hellespont, Chersonesus, and the contiguous parts as far as Mount Athos; under that of Ionia, Asia[13] and the islands of Asia; under that of Peloponnesus, Achaia, and the regions lying to the west of it. Chaldæa, when mentioned, will signify Assyria and Babylonia, as well.

My silence as to Africa,[14] Spain, and the provinces of Gaul, will occasion no surprise, from the fact that no one has published any observations made upon the stars in those countries. Still, however, there will be no difficulty in calculating them, even for these regions as well, on reference being made to the parallels which have been set forth in the Sixth Book.[15] By adopting this course, an accurate acquaintance may be made with the astronomical relations, not only of individual nations, but of cities even as well. By taking the circular parallels which we have there appended to the several portions of the earth respectively, and applying them to the countries in question, that are similarly situate, it will be found that the rising of the heavenly bodies will be the same for all parts within those parallels, where the shadows projected are of equal length. It is also deserving of remark, that the seasons have their periodical recurrences, without any marked difference, every four years, in consequence of the influence[16] of the sun, and that the characteristics of the seasons are developed in excess every eighth year, at the revolution of every hundredth moon.