General History of Europe systematic scientific research, and their books were regarded as authorities for nearly two thousand years, until science took a new start in modern times. The most famous mathematician among them was Euclid. His system of geometry was so logically built up that in modern Eng- land Euclid's geometry is still retained as a schoolbook the oldest schoolbook in use today. The Ptolemies built an astronomical observatory at Alexandria, and although it was, of course, without tele- scopes, important observations and discoveries were made. An astronomer of little fame, named Aristarchus, who lived on the island of Samos, even discovered that the earth and the planets revolve around the sun, though few people would believe him and his discovery was forgotten. Astronomy greatly aided in the progress of geography. Eratosthenes, a mathematical astronomer of Alexandria, very cleverly computed the size of the earth. Much new infor- mation had also been gained regarding the extent and the char- acter of the regions reached by explorers in this age, from the eastern coast of India to the British Isles. Eratosthenes was therefore able to write a more accurate geography than anyone before his time. It contained the first map bearing a cross-net of lines indicating latitude and longitude. This enabled him to locate any spot on land or sea far more accurately than had been possible before. HELLENISTIC PORTRAIT HEAD IN BRONZE This magnificent head of an unknown man, with wonderful representation of the hair, was recovered from the bottom of the sea. It is now In the Museum of Athens
