ANNUS,
the Year. 'Tis, properly speak∣ing, that Time which the Sun takes in passing through the 12 Signs of the Zodiack. After several Observations, Astronomers having deter∣min'd, That the several Recesses of the Sun have certain Periods, after which that Planet seems to return to the same Points, in respect to us, and much about the same time makes the same Alteratoins of Seasons, and Temperature of the Air; call'd the Year that Number of Days which the Sun is passing through those several differences of Di∣stances and Recesses.
Those who observ'd these things with grea∣ter Exactness, did first acknowledge, That the Sun did run from East to West, round the Earth in twenty four Hours, by the swift Motion of the Pri∣mum Mobile, or Highest Orb. Then they ob∣serv'd, That the Sun, besides this Motion which is common to all the Planets, had another also proper to it self, which was from West to East, round the same Globe of Earth, in the Ecliptick, which cut∣ting the Aequator obliquely, rises on both sides to∣wards the Poles, as far as the Tropicks. And lastly, That the Sun running, in one Year. through the full Extent of this great Circle of the Ecliptick, which they have divided into twelve Parts or Signs, by its Motion causes two very different Seasons, viz. Summer and Winter, when it arrives at the Tropicks, that is to say, at the two Points of the Solstices; and two other more temperate, viz. Spring and Autumn, when the Sun cuts the Ae∣quator, or the Aequinoctial.
The Year is call'd in Greek 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉 and 〈 in non-Latin alphabet 〉〈 in non-Latin alphabet 〉, that is to say, Returning into it self; whence it is, that the Egyptians have represented the Year by a Serpent turning round and biting its Tail: which made Virgil say in his Georgicks, lib. 2. v. 402.
Atque in se sua pervestigia volvitur annus.
The Year is either Natural, which is other∣wise call'd Tropical, or Civil. The Natural or Tropick Year is that exact Space of Time which the Sun takes in passing through the Ecliptick, which is not always the same, be∣cause of the Inequality of the Sun's Motion; which seems to have been observ'd in the most antient Times by the Aegyptian Priests, and Sacrificers to Jupiter Ammon, by means of the different Quantity of Oyl which was burnt continually before the Statue of that God; for measuring with all the exactness possible what they spent in the whole year, they found that there was a considerable Difference between one Year and another, and from thence infer'd that the Years were not exactly equal.
Astronomers have since by the Exactness of their Calculations and Observations, proved that the Mechanical Conjecture of the Aegypti∣ans for the Term of the Solar Year, observ'd in the time of Hipparchus and Piolemy, and a∣bout 750 years after by Albategnius, was still found very different in the time of Alphonsus King of Castile, which was about 400 years af∣ter, and the Modern Discoveries that have been made from the most curious and diligent Observations have no Agreement with the Antients.
And as the Duration of the Solar Year, which we have from Ptolemy's Observations, is the greatest of all, that in Albategnius the least, so that in Alphonsus's time is in some sort a Mean between both, but that of our time seems to come near the greatest. Copernicus, who liv'd about the end of the last Age but one, took occasion to conjecture that these, tho different Inequalities, had their deter∣min'd Periods; and that, in a certain Revo∣lution of time, they pass'd through all these Differences, and then return'd to the same Posture they were in before.
He has found out, by a laborious Computa∣tion, that the Term of this Period is about 1716 years, in which time the Solar year runs through all these several Changes.
But because it would be very hard to fix up∣on a Computation of Years, according to such nice Differences, which consist in some few Minutes for each year, the Astronomers have, for that reason, made use of a mean Duration between the greater and the less, which con∣tains 365 days, 15 hours, and about 49 mi∣nutes.
The Civil Year, which is commonly us'd by all Nations is very different, both as to its Beginning and Duration; which nevertheless may be refer'd to three different Heads, for