“The sign - indicates the years before our era, the sign + the year of our era; and the last line, at the end of each sign under the title of duration, gives the extent of the constellation in degrees, and the time which the equinox, or the solstice, occupies in traversing the constellation from one end to the other.
“The precession of 50″ yearly has been supposed, this being the result of the comparison of the catalogue of Hipparchus with the modern catalogues. We have thus the advantage of round numbers, and a general accuracy that may be relied upon. The entire period is thus 25,920 years; the semiperiod, 12,960 years; the quarter period, 6480 years; the twelfth, or a sign, 2160 years.
“It is to be remarked, that the constellations leave empty spaces between them, and that sometimes they encroach upon each other. Thus, between the last star of Scorpio, and the first of Sagittarius, there is an interval of 6⅔ degrees. On the other hand, the last of Capricorn is more advanced by 14° in longitude, than the first of Aquarius. Hence, even independently of the inequality of the sun’s motion, the constellations would afford a very unequal and very erroneous measure of the year and its months. The signs of 30° furnish a more convenient and less defective one. But the signs are merely a geometrical conception; they can neither be distinguished nor observed; and they are continually changing place from the retrogradation of the equinoxial point.
“We have at all times been able to determine, in a rough manner, the equinoxes and solstices; at the long run it has been remarked, that the appearance of the heavens was no longer exactly the same that it anciently was at the times of the equinoxes and solstices. But we have never been able to observe exactly the heliacal rising of a star, being always necessarily some days wide of it; and people frequently speak of it, without possessing a fixed datum on which to count. Before Hipparchus, we find nothing, either in books or in traditions, that can be submitted to calculation; and it is this which has given rise to so many systems. Controversies have arisen without a sufficient knowledge of the subject. Those who are not astronomers may form ideas as beautiful as they please of the knowledge of the Chaldeans, Egyptians, &c.; no real inconvenience will result. The enterprise and knowledge of the moderns may be lent to these nations, but nothing can be borrowed from them; for they have either had nothing, or they have left nothing. Astronomers will never derive from the ancients any thing that can be of the slightest utility. Let us leave to the learned their vain conjectures, and confess our utter ignorance respecting things of little use in themselves, and of which no monument remains.
“The limits of the constellations vary according to the authors which we consult. We find these limits extend or contract, as we pass from Hipparchus to Tycho, from Tycho to Hevelius, from Hevelius to Flamstead, Lacaille, Bradley, or Piazzi.
“I have said elsewhere, the constellations are good for nothing, unless at the most to enable us to mark the stars with more ease; whereas the stars in particular afford fixed points to which we can refer the motions, whether of the colures or of the planets. Astronomy commenced only at the period when Hipparchus made the first catalogue of the stars, measured the revolution of the sun, that of the moon, and their principal inequalities. The rest presents nothing but darkness, uncertainty, and gross error. The time would be lost that were occupied in attempting to reduce this chaos to order.
“I have given, with the exception of a few particulars, the whole of my opinion on this subject. I am nowise anxious about making converts, for it gives me little concern whether my ideas be adopted or not; but, if my reasons be compared with the reveries of Newton, Herschell, Bailly, and so many others, it is not impossible but that, in time, these more or less brilliant chimeras will no longer be relished.
“I have attempted to determine the extent of the constellations, according to the catasterisms of Eratosthenes; but the thing is really impossible. The matter would be still worse were we to consult Hygin, and especially Firmicus. The following is what I have made out from Eratosthenes.
| CONSTELLATIONS. | DURATIONS. | CONSTELLATIONS. | DURATIONS. |
| Years. | Years. | ||
| Aries, | 1747 | The Talons, | 1089[219] |
| Taurus, | 1826 | Scorpio, | 1823 |
| Gemini, | 1636 | Sagittarius, | 2138 |
| Cancer, | 1204 | Capricorn, | 1416 |
| Leo, | 2617 | Aquarius, | 1196 |
| Virgo, | 3307 | Pisces, | 2936 |