Alexander of Macedon was not a man likely to permit the existence of impediments in the way of that which he knew to be highly conducive to national progress and prosperity--namely, the expansion of commerce and facility of communication. On his return, therefore, from India to Susa, he, in person, surveyed the course of the Euphrates and Tigris, and gave directions for the removal of the cataracts and dams, which had so long rendered the upper waters of these rivers inaccessible from the sea. His wise plans and splendid schemes were cut short by his early death, B.C. 324; but his surviving generals, though they quarrelled with each other, did their best to carry out his policy and the measures which he had concerted with so much sagacity. His successor, Seleucus, entertained so high an opinion of the advantages to be derived from commercial intercourse with India that he organized another expedition, which must have been very successful, though no particulars of it have come down to us. He also sent to Sandracottus, King of the Prasii, an ambassador, Megasthenes, who penetrated to Palebothra (the modern Allahabad), at the confluence of the Jumna and the Ganges. Meanwhile Ptolemy Soter, another of Alexander’s generals, who had enjoyed his confidence and entered into his plans more thoroughly than any of his other officers, took possession of Egypt, and strove to secure for Alexandria the advantage of the trade with India. Some say that it was he who erected the lighthouse at the mouth of the harbour of Alexandria which was regarded as one of the seven wonders of the world, who built there the magnificent temple of Serapis, and who founded the celebrated library and museum for the benefit of learning and the cultivation of science.[39] [39] See Appendix H. His son, Ptolemy Philadelphus, completed those works, and, further to attract the Indian trade to Alexandria, commenced to form a canal, one hundred and seventy-five feet wide, and forty-five feet deep, between Arsinoe (Suez) and the eastern branch of the Nile, by means of which the productions of India might be conveyed to Alexandria entirely by water. But this work was never finished, and as the navigation of the northern extremity of the Arabian Gulf (the Red Sea) was so difficult and dangerous as to be greatly dreaded, Ptolemy built a city, which he called Berenice, further down the west coast of that sea, about lat. 24°. This new city soon became the chief port of communication between Egypt and India. Goods landed there were carried by camels across the desert of Thebais to Coptos, a distance of about 320 English miles, and from there down the Nile to Alexandria, whence they were transhipped to the various countries on the Mediterranean.