3. At a period before authentic history begins, it is probable that roving tribes of shepherds from the north took possession of the hills and valleys of Greece. Shut off on the north by mountain ranges, and on all other sides surrounded by the sea, these tribes were able to maintain a sturdy independence for many hundred years. The numerous harbors and bays which subdivide Greece invited to a maritime life, and at a very early time, the descendants of the original shepherds became skillful navigators and courageous adventurers. 4. The voyages of Aeneas and Ulysses in the siege of Troy, and those of Jason in search of the golden fleece, and of Perseus to the court of King Minos, are the mythological accounts, embellished by imagination and distorted by time, of what were real voyages. Crossing the Mediterranean, Grecian adventurers became acquainted with the Egyptians, then the most civilized people of the world; and from Egypt they took back to their native country the germs of the arts and sciences which afterward made Greece so famous. 5. Thence improvements went forward with rapid strides. Hints received from Egypt were reproduced in higher forms. Massive temples became light and airy, rude sculpture became beautiful by conforming to natural forms, and hieroglyphics developed into the letters which Cadmus invented or improved. Schools were established, athletic sports were encouraged, aesthetic taste was developed, until in the arts, in philosophy, in science, and in literature the Greeks took the lead of all peoples. 6. As population increased, colonies went out, settling upon the adjacent coasts of Asia and upon the islands farther west. In Asia the Greek colonists were subject to the Persian Empire, which then extended its rule over all Western Asia, and claimed dominion over Africa and Eastern Europe. The Greeks, fresh from the freedom of their native land, could not patiently endure the extortions of the Persian government, to which their own people submitted without question; hence conflicts arose which finally culminated in Persia taking complete possession of the Asiatic Greek cities. 7. But the ties of kinship were strong, and the people of Greece keenly resented the tyranny which had been exercised over their countrymen, and an irrepressible conflict arose between the two nations. The Persian king, Darius, determined to put an end to all annoyance by invading and subjugating Greece. Before the final march of his army, Darius sent heralds throughout Greece demanding soil and water as an acknowledgment of the supremacy of Persia, but Herodotus says that at Sparta, when this impudent demand was made, the heralds were thrown into wells and told to help themselves to all the earth and water they liked.