We have named here only the leaders in Greek literature, the whole array being far too great to cover in brief space. Following the older form of the drama, with its archaic character, came two later forms, the Middle and the New Comedy, in the latter of which Menander was the most famous writer, making in his plays some approach to the modern form. Philosophy left later exponents in Zeno, Epicurus, and many others, and history in Polybius, Strabo, Plutarch, Arrian, and others of note. Science, as developed by Aristotle and Hippocrates, the father of medicine, was carried forward by many others, including Theophrastus, the able successor of Aristotle; Euclid, the first great geometer; Eratosthenes and Hipparchus, the astronomers; and, latest of ancient scientists, Ptolemy, whose works on astronomy and geography became the text-books of the middle-age schools. Long before these later writers came into the field the centres of literary effort had shifted to new localities. Sicily became the field of the choicest lyric poetry, giving us Theocritus, with his charming "Idyls," or scenes of rural life, and his songful dialogues, with their fine description and delightful humor. Following him came Bion and Moschus, two other bucolic poets, whose finest productions are elegies of unsurpassed beauty. Syracuse was the home of this new field of lyric poetry, but there were other centres in which literature flourished, especially Pergamus, Antiochia, Pella, and above all Alexandria, the city founded by Alexander the Great in Egypt, and which under the fostering care of the Ptolemies, Alexander's successors in this quarter, developed into a remarkable centre of intellectual effort. The first Ptolemy made Alexandria his capital and founded there a great state institution which became famous as the Museum, and to which philosophers, scholars, and students flocked from all parts of the world. Here learned men could find a retreat from the bustle of the great metropolis which Alexandria became, and pursue their studies or teach their pupils in peace within its walls, and it is said that at one time fourteen thousand students gathered within its classic shades. Here grew up two great libraries, said to number seven hundred thousand volumes, and embracing all that was worthy of study or preservation in the writings of ancient days. Of these, one was burned during the siege of the city by Julius Caesar, but it was replaced by Marc Antony, who robbed Pergamus of its splendid library of two hundred thousand volumes and sent it to Alexandria as a present to Cleopatra.