ד.

To find the Dominical Letter, take the year and its fourth part, and add them together; divide the fum by 7, and fubtract what remains, after that divifion, from the divifor 7, the remainder gives the answer, accounting the letter A for 1, B for 2, C for 3, D for 4, E for 5, F for 6, and G for 7. The Dominical Letter for 1800 is found thus: The year and its fourth 450 make 2250. After this fum is divided by 7, there remains 3, which fubtracted from 7 leaves 4 for a remainder, which is the Dominical Letter for the year 1800.

A

Period is a feries, or circle, of a certain number of years, used for measuring or computing time. Of these there are feveral, moft of which take their names from the perfons who invented

them.

Of the Metonic period, or lunar cycle of 19 years, it is needlefs to fay any thing more.

fufficiently explained.

It has been

The

The Calippic period, fo called from its inventor Calippus, is a series of 76-years, which being elapfed, Calippus fuppofed that the new and full moons would return to the fame day of the folar year. This was intended as an improvement of the Metonic period.

The Victorian period is a feries of 532 years, arifing from the cycles of the fun and moon multiplied into one another. It was invented by Vittorius, a French clergyman, about the middle of the 5th century, and ufed by the western churches for many ages, in computing the time of Ealter, till the Gregorian reformation of the calendar.

The famous Julian period is a series of 7980 years, arifing from the multiplication of the cycles of the fun, moon, and indiction into one another. This period is faid to have been invented by Jofeph Scaliger; and is called Julian, as being adapted to the Julian year. As it commences before the creation, and beste op 19 1500 years of being completed, it therefore comprehends all other cycles, periods, and epochas, and, in fhort, the times of all 'actions and events, from the beginning of the world. Being thus a common receptacle, as it were, of all other epochas, it is of great use in re

༡

3.

ducing the years of invi they years of any given epocha to those of

another; for which purpose it was invented.

CHAP.

CHAP. LXII.

OF EPOCHAS OR ÆRAS.

AN Epocha, or Era, is a certain fixed point of

time, made famous by fome remarkable event; from whence, as from a root, the ensuing years are numbered or computed.

As there is no aftronomical confideration to render one epocha preferable to another, their conftitution is purely arbitrary, and therefore various epochas have been used at different times, and among different nations.

The Chriftian epocha is the common epocha throughout Europe, commencing on the 25th of December, the day of our Saviour's nativity; or rather, according to the ufual account, from his circumcifion, on the 1st of January. In thofel countries, which obferve the Julian calendar, ie commences from the incarnation, on the 25th of March, nine months prior to the nativity.

The author of this epocha, or way of computing from Chrift, was Dionyfius Exiguus, a Roman

abbot, about the beginning of the fixth century. Till his time the Chriftians computed their years, either from the perfecution under Dioclefian, or

I

from

from the building of Rome, or according to the custom of the people among whom they lived.

The calculations, however, of our modern aftronomers, seem plainly to prove that the Dionyfian account places the birth of our Saviour several years too late. But that is not material.

The Epocha of the Creation, according to the Jewish computation, is the year of the Julian period 953, answering to the year before Christ 3761, and commencing on the 7th of October. Hence, if we fubtract 952 from any given year of the Julian period, the remainder is the corresponding year of the Jewish epocha of the creation.

The Epocha of the Olympiads, which was used principally by the Greeks, is very famous in ancient hiftory. It took its rife from the Olympic games, which were celebrated at the beginning of every fifth year, near Olympia, a city of Elis in Peloponnefus. An Olympiad, therefore, was a period of four years; and by these periods the Greeks reckoned their time, the year in which the games were celebrated being counted the first year of each Olympiad.

The beginning of the first Olympiad is referred to the year of the Julian period 3938, or 776 years before Chrift.

The

The Epocha of the building of Rome, was the principal one among the Romans. This epocha is the year of the Julian period 3961, and anfwers to the year 752 before Christ, commencing on the 21st of April.

The Diocefian Epocha, or Epocha of the Martyrs, commences in the year of Chrift 284, and that of the Julian period 4997. It obtained its name from the great number of Chriftians who fuffered martyrdom in the reign of the emperor Dioclefian; and was generally used by Christians till the year 532, when the way of computing from the birth of Chrift began to prevail.

The Epocha of the Hegira is ufed by the Turks, Arabs, and others who profefs the Mahometan faith. It commences on the 16th of July, in the year of Christ 622, and of the Julian period '5335· ́ The word Hegira fignifies flight; the event which gave occafion to this epocha being Mahomet's flight from Mecca. The magiftrates of that city, finding that his imposture tended to disturb the public peace, were determined to cut off the author of it, to prevent the farther fpreading of the mifchief. But. Mahomet, having timely notice of their defign, fled by night to Medina, another city of Arabia, in the year of our Lord above-mentioned; and this is