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So far as mathematical genius is concerned, so far as astronomy taxed the reasoning powers, such men as Eratosthenes, Aristarchus, Hipparchus, and Ptolemy were great lights, of whom humanity may be proud; and, had they been assisted by our modern accidental inventions, they might have earned a fame scarcely eclipsed by that of Kepler and Newton.
When Eratosthenes began his labors, in the third century before Christ, it was known that the surface of the earth was spherical; he established parallels of latitude and longitude, and attempted the difficult undertaking of measuring the circumference of the globe by the actual measurement of a segment of one of its great circles.
In Alexandria, itself a monument of engineering and architectural skill, soon were to be found men whose names were destined for futurity Apollonius, Eratosthenes, Manetho.
For, in fact, the orations which were spoken by him had much more of boldness and confidence in them than those that he wrote. Eratosthenes says that often in his speaking he would be transported into a kind of ecstasy, and Demetrius, that he uttered the famous metrical adjuration to the people, By the earth, the springs, the rivers, and the streams, as a man inspired, and beside himself.
The remaining two-thirds were supposed to be covered by the ocean, and Eratosthenes prophetically remarked that "if it were not that the vast extent of the Atlantic Sea rendered it impossible, one might almost sail from the coast of Spain to that of India along the same parallel." Sixteen hundred years later, as we shall see, Columbus tried to carry out this idea.
The distance between Syene and Alexandria being known to be 5,000 stades, this gave for the circumference of the earth 250,000 stades, which Eratosthenes seems later, for some reason, to have changed to 252,000 stades. On the most probable assumption as to the length of the stade used, the 252,000 stades give about 7,850 miles, only 50 miles less than the true polar diameter.
It is mentioned, and a short description given of it, by Onesicritus and Eratosthenes. Iambulus, however, who lived in the time of Augustus, is the first author who enters into any details regarding it; and though much of what he states is undoubtedly fabulous, yet there are particulars surprizingly correct, and such as confirm his own account, that he actually, visited the island.
The Apennines end at the southeast in the ring mountain, Eratosthenes, thirty-eight miles across and very deep, one of its encircling chain of peaks rising 16,000 feet above the floor, and about half that height above the level of the Mare Imbrium. The shadows cast by Eratosthenes at sunrise are magnificent.
Eratosthenes says that Olympias, when she attended Alexander on his way to the army in his first expedition, told him the secret of his birth, and bade him behave himself with courage suitable to his divine extraction. Others again affirm that she wholly disclaimed any pretensions of the kind, and was wont to say, "When will Alexander leave off slandering me to Juno?"
Such men, however, are rarely found, but there have been such at times; for example, Aristarchus of Samos, Philolaus and Archytas of Tarentum, Apollonius of Perga, Eratosthenes of Cyrene, and among Syracusans Archimedes and Scopinas, who through mathematics and natural philosophy discovered, expounded, and left to posterity many things in connexion with mechanics and with sundials.
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