1 62 TRAVELS TO DISCOVER 



We cannot niiflake this, if wc obferve how anxiouily theyr 

 have varied the; figure of the top, or point of. each obelifk;; 

 fome times it is a very fharp one ; fometimes a portion of 

 a circle, to try to get rid of the great impediment that per- 

 plexed them, the penumbra. 



The projection -of the pavements, conftantly to the north- 

 ward, fo diligently levelled, and made into exact. planes by 

 large flabs of granite, molt artificially joined, have been fo 

 fubitantially fecured, that they might ferve for the obferva- 

 tion to this day ; and it is probable, the pofition of this city 

 and the well were coeval, the refult of intention, and both 

 the works of thefe firfl aftronomers, immediately after the 

 building of Thebes. If this was the cafe, we may conclude,, 

 that the fact of the fun illuminating the bottom of the well i 

 in Eratoflhenes's time was a fuppofed one, from the uniform - 

 tradition, that once it had been fo, the periodical change 

 of the quantity of the angle, made by the equator and 

 ecliptic, not being then known, and therefore that the 

 quantity of the celeftial arch, comprehended between Alex- 

 andria and Syene, might be as erroneous from another 

 caufe, as the bafe had been by amiming a wrong diftance: 

 on the earth, in place of one exactly meafured... 



There is at A-xum an obelifk erected by Ptolemy Everge- 

 tes, the very prince who was patron to Eratofthenes, with- 

 out hieroglyphics, directly facing the fouth, with its top 

 iirfl cut into a narrow neck, then fpread out like a fan in 

 a femicircular form, with a pavement curioufly levelled to. 

 receive the fhade, and make the feparation of the true fha~- 

 dow from the penumbra as diilinct as poffible. 



This 



