i 5 8 TRAVELS TO DISCOVER 



half, was not really made by him, but was fome old Chal- 

 daic, or Egyptian obfervation, made by more inftructed aftro- 

 nom'ers which he had fallen upon. 



The Arabs call it AfTouan, which they fay fignifies enlight- 

 ened; in allufion,I fuppofe, to the circumflance of the well, 

 enlightened within by the fun's being ftationary over it in 

 June; in the language of Beja its name fignifies a circle, or 

 portion of a circle. 



Syene, among other things, is famous for the firfl attempt 

 made by Greek aftronomers to afcertain the meafure of the 

 circumference of the earth. Eratofthenes, born at Cyrene a- 

 bout 276 years before Chrift, was invited from Athens to A- 

 lexandria by Ptolemy Evergetes, who made him keeper of 

 the Royal Library in that city. In this experiment two po- 

 fitions were aflumed, that Alexandria and Syene were ex- 

 actly 5000 ftades diftantfrom each other, and that they were 

 prccifely under the fi^me meridian. Again, it was verified by 

 the experiment of the well, that, in the fummer folftice at 

 mid-day, when the fun was in the tropic of Cancer, in its 

 greateft northern declination, the well* at that inftant was 

 totally and equally illuminated ; and that no ftyle, or gno- 

 mon, erected on a perfed plane, did call, or project, any 

 manner of fhadow for 150 ftades round, from which it was 

 juftly concluded, that the fun, on that day, was fo exactly 

 vertical to Syene, that the center of its difk immediately cor- 

 responded to the center of the bottom of the well. Thefe 

 preliminaries being fixed, Eratofthenes fet about his obfer- 

 vation thus : — 



On 



* Strabo, lib. ii. p. 133. 



