They had but one adventure in their five months' cruise to the Persian Gulf, but we have a graphic account of how the terrified Greeks met a shoal of whales and how they frightened the whales away. Here is the story. One day towards daybreak they suddenly saw water spouting up from the sea, as if being violently carried upwards by whirlwinds. The sailors, feeling very frightened, asked their native guides what it meant. The natives replied that it was caused by whales blowing the water up into the air. At this explanation the Greek sailors were panic-stricken and dropped the oars from their hands. Nearchus saw that something must be done at once. So he bade the men draw up their ships in line as if for battle and row forward side by side towards the whales, shouting and splashing with their oars. At a given signal they duly advanced, and when they came near the sea-monsters they shouted with all their might and blew their trumpets and made all possible noise with their oars. On hearing which, says the old story, "the whales took fright and plunged into the depths, but not long after came to the surface again close to the sterns of the vessels and once more spouted great jets of water. Then the sailors shouted aloud at their happy and unlooked-for escape," and Nearchus was cheered as the saviour of the fleet. It is not uncommon to-day for steamers bound from Aden to Bombay to encounter what is called a "school of whales" similar to those which alarmed the fleet of Nearchus in the year 323 B.C. The expedition was completely successful and Nearchus pioneered his fleet to the mouth of the Euphrates. But the death of Alexander the Great and the confusion that followed set back the advance of geographical discovery in this direction for some time. [Illustration: ALEXANDRIA IN PIZZIGANI'S MAP, FOURTEENTH CENTURY. The river with the buildings on its bank is the Nile.] Alexandria--one of the many towns founded by Alexander--had become the world centre of the learned from Europe, Asia, and Africa. Its position was unrivalled. Situated at the mouth of the Nile, it commanded the Mediterranean Sea, while by means of the Red Sea it held easy communication with India and Arabia. When Egypt had come under the sway of Alexander, he had made one of his generals ruler over that country, and men of intellect collected there to study and to write. A library was started, and a Greek, Eratosthenes, held the post of librarian at Alexandria for forty years, namely, from 240-196 B.C. During this period he made a collection of all the travels and books of earth description--the first the world had ever known--and stored them in the Great Library of which he must have felt so justly proud. But Eratosthenes did more than this. He was the originator of Scientific Geography. He realised that no maps could be properly laid down till something was known of the size and shape of the earth.