fhall now quit the Jews, and proceed to two other Diftributions of Years, of yet greater Moment in this Science, as being abfolutely neceffary to the right understanding of the Greek and Roman Hiftory. I mean the Olympiads and Luftra. The first of these was a Method of Computation in ufe among the Greeks, and of great Note in Chronology, as from them the Epocha of the Hiftory of that memorable People takes Date. Varro too, in his Divifion of the whole Series of Time into three Periods, begins the third or laft, which he calls the Era of true Hiftory, from the firft Olympiad. Now an Olympiad was a Space of four Years, at the Expiration of which the Olympic Games were celebrated with great Pomp and Solemnity near the City Olympia in Peloponnefus. They are faid by fome to have been first instituted by Hercules, in Honour of Jupiter. But being afterwards difcontinued for a Time, they were revived by phitus the Son of Praxonides in the 3938 Year of the Julian Period, the 3228 Year of the World, and 776 Years before Christ. From this Time they were continued without Interruption, and became the Epocha from which the Greeks computed their Years. The firft Olympiad is mark'd by the Victory of Corebus the Elean. Thefe Sports were renewed every_fifth Year, and after a Revolution of four Years compleat. They confifted of various Kinds of Exercises, in which fuch as were to enter the Lifts, took great Pains before-hand to accomplish themselves. The Conquerors were distinguished by the most particular Honours, and publickly crowned in an Affembly of all Greece. Nay, fo great was the Efteem in which they were held, that at their Return, a Piece of the Wall of the City was pulled down, to give Paffage to their Chariot. The Computation by Olympiads feems to have ceafed after the 364th, which ended with the Year of Chrift 440; for we hence-forward meet with no more Mention of them in Hiftory. The Luftrum again is a Roman Institution, and ufed by their Writers to fignify a Space of five Years. It took its Rife from the Inftitution of the Cenfus by Servius Tullius. This politic King, having diftinguished the Citizens into Claffes and Centuries, and rank'd them according to the Valuation of their Eftates, commanded them to appear on a Day appointed under Arms, and agreeable to the above-mentioned Diftribution, in the Campus Martius, which was a large plain Field, lying without the City near the Tiber. Here by the King's Order was made a folemn Luftration or expiatory Sacrifice in the Name of all the People. The Sacrifice confifted of a Sow, a Sheep, and a Bull, whence

it took the Name of Suovetaurilia: The whole Ceremony was called Luftrum, à luendo, from paying, expiating, clearing, or perhaps from the Goddefs Lua, to whom Servius is faid to have built a Temple. But because of the continual Change of Men's Eftates, it was ordered that the Cenfus fhould be renewed every five Years, and it being usually clofed by the Luftrum, it was hence that the Word came to fignify that Term of Years.

P. You have now, according to your Promife, explained all the most noted Computations of Time, whether ancient or modern. Is there any thing farther to be obferved on this Subject, before you enter upon the Confideration of Epo

chas ?

G. Epochas, as I told you before, are certain fixed Points of Time, from which Men begin their Computations, and to which in all their Calculations they refer. Hence by comparing different Tranfactions with the Epocha, and tracing their various Intervals and Distances, we can afcertain the Years in which they happened, and affign them their Place and Order in the Succeffion of Time. But it is evident that all this can regard only the Epocha immediately under Confideration. Where the different Epochas are used, as is frequenly the Cafe in Hiftory, we must neceffarily have fome common Measure by which to compare them together, and discover the Relation they bear to one another. The Creation of the World, the Deluge, the Olympiads, the Building of Rome, and the Birth of Christ, are all celebrated Æras in History, and often made ufe of in the Computation of Time. It is apparent however, that in reading the Tranfactions of different Nations, which may be referred to those or other Æras, we shall not know how to connect them together, or comprehend the coincident Times, unless we firft establish fome general Period, which may ferve as the Standard and common Receptacle of all other Epochas. This done, we have only to reduce the feveral Æras to it; which throws the whole Train of paft Events into one connected Series, and exhibits them in their diftinct Order of Succeffion. Such a Standard as that we are fpeaking of is the Julian Period. And as there is nothing more important in Chronology, than to have a diftinct Comprehenfion of this Period, and to fee the Manner of its Application, I fhall, in order to give a clearer Infight into the Subject in hand, explain firft: the Cycles of which it is compofed; then fhew, how by the artful Combination of thefe, fuch a Measure of Time is framed, as preferves a happy Diftinction in all its Parts, fo that they are A a 2

in

in no danger of being confounded or mistaken one for an other; and laftly, I fhall demonftrate the Use of this Period in regulating the several Epochas and Computations of Chronology.

The Confideration of Cycles makes properly a Part of Ecclefiaftical Computations, they being chiefly contrived for determining the New and Full Moons, and regulating the Feftivals of the Church depending thereon. In a View of Chronology therefore fuch as this, defigned only for the Ufes and Purposes of Hiftory, it will not be neceflary to confider them any farther than as they go to the Compofition of the Julian Period, and confequently make a Part of the Civil Measures of Time. Cycles in the general are no more than certain Periods or Series of Years, proceeding in an orderly Succeffion from first to laft, when they are fupposed to begin again, and fo preferve the fame Tenour in a conftant Train of Revolutions. Thus the continued Series of Sabbatical Years among the Jews, is called the Sabbatical Cycle, which thence confifted of feven Years; as a Syftem of fifty Years continually recurring, made their Jubilean Cycle. In like Manner, if we should fuppofe the Sun and Moon to set out together from any Point of the Zodiac, and after a certain Succeffion of Years to meet again in the fame Point of the Heavens; as this Event muft always happen upon the like Revolution of Years; this Number of Years would neceffarily form a Cycle, by which to determine for ever the Coincidence of these two Luminaries in the Heavens. And accordingly this is the Intent of the Lunar Cycle, or Cycle of the Moon, of fo great Note in Chronology. But in order to trace the Origin and Formation of it with the greater Exactness, we muft go back to the ancient Form of the Year in ufe among the Jews and Greeks, which tho' properly Lunar, yet as they were obliged alfo to regard the Solar Motions, hence arofe the Neceffity of Intercalations, and of establishing a Cycle to regulate and adjust these Intercalations. The Year at firft in ufe among the Jews, was not fettled by Aftronomical Rules, but made up of Lunar Months, fet out by the Phafes or Appearances of the Moon. When they faw the New Moon, then they began their Months, which confifted alternately of 29 and 30 Days, for the Reafons given above. None of them had fewer than 29 Days, and therefore they never looked for the New Moon before the Night following the 29th Day; and if they then faw it, the next Day was the firft Day of the following Month. Neither had any of their Months more than 30 Days; and there

fore

fore they never looked for the New Moon after the Night following the 30th Day, but if they faw it not then, concluded its Appearance was obftructed by Clouds; and of 12 of these Lunar Months, their common Year confifted. But as this falls 11 Days fhort of a Solar Year, every one of these common Years, in refpect of the Sun's Courfe, began 11 Days sooner than the former; which in 33 Years, would carry back the Beginning of the Year thro' all the four Seafons. This Inconvenience they were under a Neceffity of preventing for the Sake of their Feftivals. The Feast of the Paffover was fixed to the Middle of the Month Nifan, and ordered to be celebrated by the eating of the Pafchal Lamb, and the offering up of the Wave Sheaf, as the firft Fruits of their Barley Harveft. The Feaft of Pentecoft was kept the 50th Day after the 16th of Nifan, the Day on which the Wave Sheaf was offered; and celebrated by the offering of the two Wave Loaves, as the firft Fruits of their Wheat Harveft. And laftly, the Feaft of Tabernacles always began on the 15th of Tifri, being fixed to the Time of gathering in the Fruits of the Earth, It is evident therefore that the Paffover could not be observed, till the Lambs were grown fit to be eaten, and the Barley to be reaped; nor the Pentecoft till the Wheat was ripe, nor the Feast of Tabernacles till the Ingathering of the Vineyard and Oliveyard were over. And therefore these Festivals being fixed to these fet Seasons of the Year, it was neceffary to adjuft the Lunar Reckoning to the Sun's Courfe, and thereby prevent their Months from receding too far from the Seasons. For this Purpofe, fometimes in the third Year, and sometimes in the second, they caft in another Month, making the Year then confift of 13 Months; whereby they conftantly reduced their Lunar Year, as far as fuch an Intercalation could affect it, to that of the Sun, and never fuffered the one to vary from the other above a Month. Thefe Intercalations were regulated by the High-Prieft and Sanhedrim, and Notice given of what they ordained in this Matter over all the Land. But when they became difperfed over all Nations, fo as neither to have proper Opportunities of making the requifite Obfervations, nor Means of communicating them when made, it was then found neceffary to establish fixed and ftated Rules of Intercalation, that fo they might be every where uniform herein. And upon this Occafion it was, that the Cycles and Aftronomical Calculations of the Greeks, were with fome little Variation first introduced among them.

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You

You fee therefore that the Jewish Years, tho' properly and fingly confidered they were indeed Lunar, yet by these Intercalations, and the keeping of their Months conftantly fixed to the fame Seafons, they became in their collective Sums truly Solar. The fame Thing happened alfo among the Greeks, and for a like Reafon. Their Years were indeed Lunar, as confifting of Months measured by the Motion of the Moon, but at the fame time they took care to adjust these to the Solar Reckoning, for the Sake of their Feftivals, efpecially for the Sake of the Olympiads. For being directed by an Oracle to obferve all their folemn Sacrifices and Festivals xarà τsía, i. e. according to Three; and this being interpreted to mean Years, Months and Days, and that the Years were to be reckoned according to the Courfe of the Sun, and the Months and Days according to that of the Moon, they thought themfelves obliged hereby to obferve all these Solemnities, at the fame Seafons of the Year, and on the fame Month, and on the fame Day of the Month. And therefore Endeavours were made to bring all these to meet together, that is, to bring the fame Months, and all the Days of them, to fall as near as poffible within the Time of the Sun's Courfe. The Difficulty therefore lay in finding out fuch Intercalations as without difturbing the Lunar Revolutions, would by the additional Months thence arifing, keep the regular Months duly fixed to the fame Seafons. For as the Lunar Year fell only 11 Days fhort of the Solar; to have added these annually, would have broke in upon the Succeffion of their Months, and deftroyed the whole Scheme of their Year. For with them, in the fame Manner as with the Jews, their Months always began with a New Moon, and their Years were always made up of thefe Lunar Months, fo as to end exactly with the laft Day of the laft Moon, and to begin exactly with the first Day of the next Moon. It was neceffary therefore for the bringing of all to fall right according to the Directions of the Oracle, that the Intercalation fhould be made by Months; and to find out fuch an Intercalation of Months, as would at length bring the Solar Year and the Lunar Year to an exact Agreement, fo that both fhould begin from the fame Point of Time, was that which was to be done for this Purpofe. For thus only could the Solemnities be always kept to the fame Seafons of the Year, as well as to the fame Months, and the fame Days of them, and conftantly be made to fall within the Compafs of one Lunar Month at moft fooner or later, within the fame Times of the Solar Year. And therefore in order hereunto Cycles were to be