1" 



1 



THE SOURCE OF THE NILE. 161 



(almoft infurmountable) in diftinguifhing the divifion of 

 the penumbra. 



There certainly is one error very apparent, in meafuring 

 the bafe betwixt Syene and Alexandria ; that is, they were 

 not (as fuppofed) under the fame meridian ; for though, to 

 my very great concern afterwards, I had no opportunity of 

 fixing the longitude at this firft viiit to Syene, as I had done 

 the latitude, yet on my return, in the year 1 772, from an 

 eclipfe of the firft fatellite of Jupiter, I found its longitude to 

 be 2)2> Q 3°'; and the longitude of Alexandria, being 30 16' 7 

 there is 3 14/ that Syene is to the eaftward of the meridi 

 of Alexandria, or fo far from their being under the fame 

 meridian as fuppofed. 



It is impoffible to fix the time of the building of Syene ; 

 upon the moil critical examination of its hieroglyphics and 

 proportions, I mould imagine it to have been founded fome 

 time after Thebes, but before Dendera, Luxor, or Carnac. 



It would be no lefs curious to know, whether the well, 

 which Eratofthenes made ufe of for one of the terms of the 

 geodefique bafe, and his arch of the meridian, between 

 Alexandria and Syene, w r as coeval with the building of that 

 city, or whether it was made for the experiment. I ihould 

 be inclined to think the former was the cafe ; and the pla- 

 cing this city firft, then the well under the tropic, were with 

 a view of afcertaining the length of the folar year. In Ihort, 

 this point, fo material to be fettled, was the conftant object. 

 of attention of the firft aftronomers, and this was the ufe of 

 the dial of Ofimandyas ; this inquiry was the occafion of the 

 number of obeliiks raifed in every ancient city in Egypt. 



Vol, I. X We 



