Elementary arithmetic, with brief notices of its history... by Robert Potts.

16

ON THE DIVISIONS AND MEASURES OF TIMIE.

The fathers at the Council give no account of the reasons by
which they ordered the Western rather than the Eastern manner
to be preferred, nor even whether they consulted the astronomers
of Alexandria.
As the Julian year exceeds the true solar year by about 11' 5o",
the excess in four years amounts to 45'. This excess of 45' in the
period of 131 years amounts to one day and 35'; and hence originated
the difference of the day, when Sosigenes observed the equinox, from
that in which it was observed in 325 A.D., for which the Nicene
Council could not account.
The cause of that difference was not then ascertained. In fact, at
that time astronomical instruments had not been invented by
means of which small differences of times and motions could be
measured and estimated. It was only after long periods, when the
error had accumulated to several days, that it became so apparent as
to require correction, as at the time of the Julian correction of the
calendar, and at the settlement of the rule for finding Easter* at the
Council of Nicea. The cause of this difference was not ascertained at
the Council, though the fact was apparent, of the vernal equinox
having gone back four days.
It is reported that bishops from the British Isles attended this
Council, but it appears that the British Christians afterwards adhered to the Eastern mode of observing the festival of Easter. For
when Augustine came on his mission to the Anglo-Saxons in 596 A.D.,
or more than 200 years after this Council, he demanded that the
British Christians should conform to the Roman practice of observing
Easter. They firmly declined to submit, clearlyj proving that tho
Christian Church in Britain existed before the mission of Augustine.
The epoch of the Christian era was not used in the computation
of time for several centuries after the time of the birth of the Messiah.
Dionysius, a native of Scythia, called Exiguus, on account of his
stature, was the founder of this epoch. He was a monk, a man of
great learning, and he became an abbot at Rome in the early part
of the sixth century. He calculated that the time of the birth of
the Messiah coincided with the 25th December, 753 A.U.c., which
is now considered to be four years too late. In two letters of
Dionysius, one written in 526 A.D., and the other the year after, is
described his reformation of the calendar. The alteration proposed
he thus states:-" But since Cyrillus began his first cycle from the
153rd year of Diocletian, and finished the last in the 247th year; we,
beginning from the 248th year of that tyrant, rather than prince,
refuse to connect the memory of a blasphemer and persecutor with
our cycles, but rather choose to note the dates of our years from the
incarnation of our Lord Jesus Christ."1
Instead of reckoning the beginning of the Christian era from the
25th December, A.~U.C. 753, he made the 1st day of January, the first
month of the Julian year, to be the beginning of the Christian era,
so that the year 1 A.D. (Anno Domini) was made to coincide with 754
1 "Quia veto S. Cyrillus primum Cyclum ab anno Dioclesiani centesimo quinl
quagesimo tertio copit et ultimum in ducentesimo quadragesimo septimo terminavit,
nos a ducentesimo quadragesimo octavo anno ejusdem tyranni potius, quamn principis,
inchoantes, nolumus circulis nostris memoriam impii et persecutoris innectere, sed
magis elegimus ab incarnatione Domini nostri Jesu Christi annorum tempora
prcnotare. " —Petavii Doatr. Tezmp. sub finelm.