THK SURFACE OF THE GLOBE. 109 



But, it is said, if the ancient races have not left us any history, their 

 long existence as nations is not the less attested by the progress which 

 they made in astronomy ; by observations vphich are easily dated, and 

 even long by the monuments still existing and w^hich themselves bear 

 their dates. 



Thus the length of the year, such as the Egyptians are supposed to 

 have determined it, according to the heliacal rising of Sirius, is cor- 

 rect for a period comprised between the year 3000 and the year 1000 

 before Christ, a period to which the traditions of their conquests, and 

 the great prosperity of their empire, also have reference. This accuracy 

 proves to what an exact pitch they had carried their observations, and 

 makes it evident that they had devoted themselves for a long time to 

 such studies. 



To appreciate this reasoning, it is necessary that we enter into some 

 explanation. 



The solstice is that moment of the year, at which the rising of the 

 Nile begins, and which the Egyptians must have observed with very 

 great attention. Having in the beginning formed a civil or sacred 

 year, of exactly three hundred and sixty-five days, from imperfect 

 observations, they would preserve it from superstitious motives, even 

 after they had discovered that it did not coincide with the natural or 

 tropical year, and that the seasons did not revert on the same days.* 

 However, it was the tropical year which it most behoved them to mark 

 for directions in their agricultural operations. They would then seek 

 in the heavens for some apparent sign of its return, and they imagined 

 that they had found it when the sun returned to the same position, 

 with relation to a certain remarkable star. Thus they applied them- 

 selves, like nearly all nations, who begin a similar enquiry, to the exa- 

 mination of the heliacal rising and setting of the stars. We know 

 that they particularly fixed on the heliacal rising of Sirius ; at first, 

 doubtless, because of the splendour of this star ; and above all be- 

 cause in ancient times this rising of Sirius nearly coinciding with the 

 solstice, announcing the inundation, was to them a phenomenon of the 

 most important nature. Hence it was that Sirius, under the name of 

 Sothis, played a prominent part in all their mythology, and their reli- 

 gious rites. Supposing then that the recurrence of the heliacal rising 

 of Sirius and the tropical year were of the same duration, and believ- 

 ing that they had at length discovered that this duration was three 



* Geminus, a coatemporary with Cicero, explains these notions at length. See 

 M. Halma's edition, at the end of PtolomBeus, p. 4.3. 



