=The Hellenic Universities.=--From these two classes of schools, the philosophical and the rhetorical, the fame of Athens spread rapidly, and from the fourth century B. C. onward the number of young men from all over the civilized world who came there to study steadily increased. Before the close of the century the old cadet training of Athens was united with this intellectual education, and there sprang up a regular institution or university, which the young Athenians and students from outside might attend. Before long, the Hellenic world boasted other universities, such as those at Rhodes, Pergamon, Alexandria, and Rome. Until almost 300 A. D. Athens remained the chief intellectual center of civilization, and attracted students from all parts of the Roman Empire. Gradually, however, the higher education there tended toward the study of rhetoric alone and artificiality grew apace. In consequence, Alexandria came to displace Athens as the center of culture, and her university became the leading one of the world. Here the various philosophic and religious sects gathered to study and discuss, and the abstract Greek philosophy united with the more concrete beliefs of the Orient, especially Zoroastrianism, Judaism, and Christianity. Thus there flourished here the various systems of religious philosophy known collectively as ‘Hellenistic,’ such as Neopythagoreanism, Neomazdeism, Philonism, Gnosticism, and Neoplatonism. Considerably before this, too, there had developed at Alexandria the Ptolemaic theory of the universe. Other noted investigations, like those of Euclid in geometry, Archimedes in physics, Eratosthenes in astronomy, and Diophantus in algebra, also bore witness to the intellectual activity of this university. [Sidenote: Spread through the Orient] [Sidenote: and the Roman world.]