The projection of the pavements, constantly to the northward, so diligently levelled, and made into exact planes by large slabs of granite, most artificially joined, have been so substantially secured, that they might serve for the observation to this day; and it is probable, the position of this city and the well were coeval, the result of intention, and both the works of these first astronomers, immediately after the building of Thebes. If this was the case, we may conclude, that the fact of the sun illuminating the bottom of the well in Eratosthenes’s time was a supposed one, from the uniform tradition, that once it had been so, 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 celestial arch, comprehended between Alexandria and Syene, might be as erroneous from another cause, as the base had been by assuming a wrong distance on the earth, in place of one exactly measured. There is at Axum an obelisk erected by Ptolemy Evergetes, the very prince who was patron to Eratosthenes, without hieroglyphics, directly facing the south, with its top first cut into a narrow neck, then spread out like a fan in a semicircular form, with a pavement curiously levelled to receive the shade, and make the reparation of the true shadow from the penumbra as distinct as possible. 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.