A HISTORY OF SCIENCE 



dilations of Biot, the heliacal rising of Sothis at the 

 solstice was noted as early as the year 3285 B.C., and 

 it is certain that this star continued throughout sub- 

 sequent centuries to keep this position of peculiar 

 prestige. Hence it was that Sothis came to be asso- 

 ciated with Isis, one of the most important divinities 

 of Egypt, and that the day in which Sothis was first 

 visible in the morning sky marked the beginning of the 

 new year; that day coinciding, as already noted, with 

 the summer solstice and with the beginning of the Nile 

 flow. 



But now for the difficulties introduced by that un- 

 reckoned quarter of a day. Obviously with a calendar 

 of 365 days only, at the end of four years, the calendar 

 year, or vague year, as the Egyptians came to call it, 

 had gained by one full day upon the actual solar year 

 that is to say, the heliacal rising of Sothis, the dog- 

 star, would not occur on new year's day of the faulty 

 calendar, but a day later. And with each succeeding 

 period of four years the day of heliacal rising, which 

 marked the true beginning of the year and which still, 

 of course, coincided with the inundation would have 

 fallen another day behind the calendar. In the course 

 of 120 years an entire month would be lost; and in 480 

 years so great would become the shifting that the sea- 

 sons would be altogether misplaced; the actual time 

 of inundations corresponding with what the calendar 

 registered as the seed-time, and the actual seed-.time 

 in turn corresponding with the harvest-time of the 

 calendar. 



At first thought this seems very awkward and con- 

 fusing, but in all probability the effects were by no 



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