Eratosthenes was gifted in all the branches of knowledge of his time but failed to top his contemporaries in any one branch. This is the reason, some suppose, that he was nicknamed “Beta.” He was an outstanding athlete, poet, astronomer, geographer, historian, and mathematician, and various of his works are mentioned by later writers. We have already seen, in Problem Study 4.3 (c), his mechanical solution of the duplication problem. His most scientific achievement, the measurement of the earth, is considered in Problem Study 6.1 (c).