Page:Philosophical Transactions - Volume 002.djvu/167

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A Method

For finding the Number of the Julian Period for any Year assign'd, the Number of the Cycle of the Sun, the Cycle of the Moon, and of the Indictions for the same year, being given; together with the Demonstration of that Method.

In these Transactions, N° 18. p. 324. is a Theorem for finding the Year of the Julian Period by a new and very easie Method, which was taken out of the Journal des Scavans, N° 36. as it had been proposed and communicated by the Learned Jesuit De Bill.

Multiply the

$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Solar	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	Cycle	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$
	Lunar
	Indication

by

$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	4845.	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$
	4200.
	6916.

Then divide the sum of the Products by 7980 (the Julian Period) the Remainder of the Division, without having regard to the Quotient, shall be the Year inquired after.

Some Learned Mathematicians of Paris, to whom the said P. de Billy did propose this Problem, have found the Demonstration thereof as the same Journal intimates.

There being no further Elucidation of the said Theorem since publish'd, Mr. John Collins, now a Member of the Royal Society, communicated what follows, viz.

That the Julian Period is a Basis, whereon to found Chronology not liable to Controversie, as the Age of the World is: And 'tis the Number abovesaid, to wit, 7980, which-is. the Product of

$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	28	$\scriptstyle {\left.{\begin{matrix}\ \\\\\ \ \end{matrix}}\right\}\,}$
	19
	15

the

$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Solar	$\scriptstyle {\left.{\begin{matrix}\ \\\ \end{matrix}}\right\}\,}$	Cycle
	Lunar
	Indication

Concerning this Julian Period, the late Archbishop of Armagh, Usher, in the Preface to his Learned Annals, advertiseth, that Robert Lotharing, Bishop of Hereford, first observed the Conveniencics thereof; 500 years after whom, it was fitted for Chronological uses by Joseph Scaliger, and is now embraced by the Learned as such a limit to Chronology, that within the space of 7980 Years, the Number of the Sun's Cycle, the Prime, and the year of the Roman Indiction (which relates to their ancient Laws

and