This was probably intended for verifying the experiment of Eratosthenes with a larger radius, for, by this obelisk, we must not imagine Ptolemy intended to observe the obliquity of the ecliptic at Axum. Though it was true, that Axum, by its situation, was a very proper place, the sun passing over that city and obelisk twice a-year, yet it was equally true, that, from another circumstance, which he might have been acquainted with, at less expence of time than building the obelisk would have cost him, that he himself could not make any use of the sun's being twice vertical to Axum; for the sun is vertical at Axum about the 25th of April, and again about the 20th of August; and, at both these seasons, the heaven is so overcast with clouds, and the rain so continual, especially at mid-day, that it would be a wonder indeed, if Ptolemy had once seen the sun during the months he staid there.
Though Syene, by its situation should be healthy, the general complaint is a weakness and soreness in the eyes; and this not a temporary one only, but generally ending in blindness of one, or both eyes; you scarce ever see a person in the street that sees with both eyes. They say it is owing to the hot wind from the desert; and this I apprehend to be true, by the violent soreness and inflammation we were troubled with in our return home, through the great Desert, to Syene.
We had now finished every thing we had to do at Syene, and prepared to descend the Nile. After having been quiet, and well used so 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,
