This war engrossed the attention of all classes at home, so that the philosophers were enabled to prosecute their studies unmolested. It also in many other ways was a means of furthering the scientific efforts of that and of future ages. For the first time the Macedonians beheld the ebbing and flowing of the tides; they discovered and examined the Chaldean astronomical instruments, and learnt their calculations, extending over several thousand years; and they observed the Chaldean division of the zodiac into twelve portions, and of the day and night into twelve hours each. The particulars of these they sent home to Aristotle. What a field was here opened out for Greek speculation! The Chaldeans had detected the precession of the equinoxes, and were well acquainted with the causes of eclipses; they printed from a revolving roller, on which they had engraved cuneiform letters; they possessed magnifying instruments; and were, in fact, the tail-end of a mighty and advanced Accadian civilisation which had been in existence for thousands of years. Not satisfied with these achievements, the conquering Alexander next subdued the ancient monarchy of Egypt, learnt the great feat of the Pharaohs—viz., the circumnavigation of Africa by the Cape of Good Hope and the pillars of Hercules, and founded the celebrated city of Alexandria. He died at Babylon B.C. 323, after which his huge empire was divided among his generals; his half brother, Ptolemy Soter, who had been governor of Egypt during Alexander’s lifetime, taking possession of that country, and establishing his seat of government at the new city of Alexandria.