JULIAN PERIOD. 



diction, which have just been explained. To find a certain 

 number of years, which is at the same time an exact multiple of 

 each of these cycles, we have only to multiply together the 

 number of years in each of them. Thus, if we multiply 19 by 15, 

 we shall obtain 285 years, which consists of exactly 15 cycles of 

 Meton and 19 Indictions. Again, if this last number, 285, be 

 multiplied by 28, we shall obtain 7980 years, which consists of 

 exactly 285 solar cycles, or of 420 Metonic cycles, or, in fine, of 

 532 Indictions. 



This interval of 7980 years was proposed as a common historical 

 and chronological period, by the celebrated historian Joseph 

 Scaliger, who gave it the name of the JULIAN PEEIOD. 



48. For the purposes of history and chronology, it was not, 

 however, enough to suggest such a cycle. It was necessary to 

 discover its natural and proper starting-point or era. Supposing 

 that we are now at some point in such a current cycle, what is 

 that point ? or, which is the same thing, what was the first year 

 of the period ? 



Since the period proposed consists of an exact number of cycles 

 of Meton, an exact number of Indictions, and an exact number of 

 solar cycles, it is evident that its natural and proper commence- 

 ment must be the year which was at the same time the first of 

 a Metonic cycle, the first of a solar cycle, and the first of an In- 

 diction. Now, as we know the first years respectively of each of 

 these current cycles, it is only necessary to count each of the three 

 back into past times until we find a year which is at once the first 

 year of each of the three. That year will then be the first year 

 of the current Julian period. 



This is precisely what Scaliger did. He took, for example, the 

 first year of the then current Metonic cycle, and counting back 

 from 19 years to 19 years, made a table of the first years of each 

 cycle, expressed with reference to the Christian era. He then 

 took in like manner the first year of the current Indiction, and by 

 counting back from 15 years to 15 years, made a like table of the 

 dates. He then took the first year of the current solar cycle, and 

 made a similar table. In these tables he sought and found the year 

 before Christ which was a first year of the Metonic cycle, a first 

 year of the Indiction, and a first year of the solar cycle. This 

 was the year 4713 B.C. 



He therefore fixed the commencement of the Julian period 

 at the year 4713 B.C., or, to be still more precise, on the 

 1st of January in that year, at the moment of mean noon for the 

 meridian of Alexandria, that being the place at which the observa- 

 tions of Ptolemy were made, and to which the tables of that 

 celebrated astronomer and observer were related. 



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