"Canopus was fully 1° 20' below the horizon of Toledo (39° 54' north latitude) in the time of Columbus; and now the same star is almost as much above the horizon of Cadiz. While at Berlin, and in northern latitudes, the stars of the Southern Cross, as well as α and β Centauri, are receding more and more from view, the Magellanic Clouds are slowly approaching our latitudes. Canopus was at its greatest northern approximation during last century [eighteenth], and is now moving nearer and nearer to the south, although very slowly, owing to its vicinity to the south pole of the ecliptic. The Southern Cross began to become invisible in 52° 30' north latitude 2900 years before our era, since, according to Galle, this constellation might previously have reached an altitude of more than 10°. When it had disappeared from the horizon of the countries of the Baltic, the great pyramid of Cheops had already been erected more than five hundred years. The pastoral tribe of the Hyksos made their incursion seven hundred years earlier. The past seems to be visibly nearer to us when we connect its measurement with great and memorable events."[502] With reference to the great Grecian philosopher and scientist Eratosthenes of Cyrene, keeper of the Alexandrian Library under Ptolemy Euergetes, Carl Snyder says, "Above all the Alexanders, Cæsars, Tadema-Napoleons, I set the brain which first spanned the earth, over whose little patches these fought through their empty bootless lives. Why should we have no poet to celebrate so great a deed?"[503] And with reference to Aristarchus he says, "If grandeur of conceptions be a measure of the brain, or ingenuity of its powers, then we must rank Aristarchus as one of the three or four most acute intellects of the ancient world."[504] Lagrange, who often asserted Newton to be the greatest genius that ever existed, used to remark also--"and the most fortunate; we do not find more than once a system of the world to establish."[505] Grant says-- "Lagrange deserves to be ranked among the greatest mathematical geniuses of ancient or modern times. In this respect he is worthy of a place with Archimedes or Newton, although he was far from possessing the sagacity in physical enquiries which distinguished these illustrious sages. From the very outset of his career he assumed a commanding position among the mathematicians of the age, and during the course of nearly half a century previous to his death, he continued to divide with Laplace the homage due to pre-eminence in the exact sciences. His great rival survived him fourteen years, during which he reigned alone as the prince of mathematicians and theoretical astronomers."[506]