Eratosthenes

Eratosthenes was a Greek scholar from Cyrene in North Africa who became director of the Library of Alexandria. He worked across geography, astronomy, mathematics, chronology and poetry.

He is best known for making the first measurement of the size of the Earth for which details survive. Comparing the angle of the noon Sun at Syene (Aswan) and Alexandria, and the distance between them, he estimated the Earth's circumference with remarkable closeness. He also drew a map of the known world with lines of latitude and longitude and tried to fix dates for Greek history.

His own geographical works are lost and survive mainly through later writers, especially Strabo. One such report concerns Helike, the city destroyed by earthquake and sea in 373 BCE. According to Strabo, Eratosthenes had been told by ferrymen that a bronze statue of Poseidon still stood upright in the water there, a danger to fishermen's nets.