THE SOURCE OF THE NILE. 163 



This was probably intended for verifying the experi- 

 ment of Eratofthenes with a larger radius, for, by this 

 obelifk, we mull not imagine Ptolemy intended to obferve 

 the obliquity of the ecliptic at Axum. Though it was 

 true, that Axum, by its fituation, was a very proper place, the 

 fun palling over that city and obeliflc twice a-year, yet it 

 was equally true, that, from another circumllance, which 

 he might have been acquainted with, at lefs expence of time 

 than building the obelifk would have cod him, that he 

 himfelf could not make any ufe of the fun's being twice 

 vertical to Axum ; for the fun is vertical at Axum about the 

 25th of April, and again about the 20th of Augufl ; and, at 

 both thefe feafons, the heaven is fo overcaf! with clouds, 

 and the rain fo continual, efpecially at mid-day, that it 

 would be a wonder indeed, if Ptolemy had once fcen the fun 

 during the months he ftaid there. 



Though Syene, by its fituation mould be healthy, the 

 general complaint is a weaknefs and forenefs in the eyes ; 

 and this not a temporary one only, but generally ending in 

 blindnefs of one, or both eyes ; you fcarce ever fee a perfon 

 in the ltreet that fees with both eyes. They fay it is owing 

 to the hot wind from the defert ; and this I apprehend to 

 be true, by the violent forenefs and inflammation we were 

 troubled with in our return home, through the great Defert, 

 to Syene. 



We had now fmifhed every thing we had to do at Syene, 

 and prepared to defcend the Kile. After having been quiet' 

 and well ufed fo long, we did not expect any altercation at 

 parting ; we thought we had contented every body, and we 

 were perfectly content with them. But, unluckily for us, 



X 2 our 



