This observation surely therefore is not worth recording, unless to shew the insufficiency or imperfection of the method ; it cannot deserve the encomiums *[1] that have been bestowed upon it, if justice has been done to Eratosthenes' geodesique measures, which I do not, by any manner of means, warrant to be the case, because the measure of his arch of the meridian seems to have been conducted with a much greater degree of success and precision than that of his base.
On the 22d, 23d, and 24th of January, being at Syene, in a house immediately east of the small island in the Nile (where the temple of Cnuphis is still standing, very little injured, and which †[2] Strabo, who was himself there, says was in the ancient town, and near the well built for the observation of the solstice) with a three-foot brass quadrant, made by Langlois, and described by ‡[3] Monsieur de la Lande, by a mean of three observations of the sun in the meridian, I concluded the latitude of Syene to be 24° 0' 45" north.
And, as the latitude of Alexandria, by a medium of many observations made by the French academicians, and more recently by Mr Niebuhr and myself, is beyond possibility of contradiction 31° 11' 33", the arch of the meridian contained between Syene and Alexandria, must be 7° 10' 48", or 1' 12" less than Eratosthenes made it. And this is a wonderful precision, if we consider the imperfection of his instrument, in the probable shortness of his radius, and difficulty
