Why was this immense wall erected? The Chinese are a peaceful people, and they surrounded themselves with walls to prevent intrusion from outside. In China there are 1553 towns enclosed in massive stone walls, and the great emperor in the third century B.C. naturally thought of building a wall in the same way all round his extensive kingdom. It was principally from the north that danger threatened. There lived the nomads of Eastern Turkestan and Mongolia, savage, brave, and warlike horsemen. To them the Chinese wall was an insurmountable obstacle. But precisely on that account this wall has also affected the destiny of Europe, for the wild mounted hordes, finding the way southwards to China barred, advanced westwards instead, and in the fourth century, in conjunction with the Alans, overran extensive areas of Europe. The Great Wall, however, could not protect China for ever. In the year 1280 the country was conquered by Jenghis Khan's grandson, Kublai Khan, Marco Polo's friend and patron. He, too, was a great builder. He constructed the Grand Canal (see map, p. 174) between Peking and Hang-chau, immediately to the south-west of Shanghai. His idea was that the rice harvest of the southern provinces should also benefit the northern parts of the country. Previously the rice had been freighted on junks and carried along the coast, where it was exposed to the attacks of Japanese pirates. Now the junks could pass safely through the country by the new canal. The imperial canal is 840 miles long, crosses the Yellow and Blue rivers, and is still in use. It is a memorial of the hundred years' rule of the Mongols. In 1644 China was conquered by the Manchu dynasty, which still reigns. Exactly a hundred years earlier the Portuguese had seized Macao, not far from Hong Kong. Since then, and particularly during recent decades, Europeans have encroached on Chinese soil. The French possessions on the peninsula of Further India were formerly under Chinese protection. The Great Powers have made themselves masters of some of the best harbours in China. On two occasions, the latter during the Boxer insurrection in 1900, Peking has been entered by the combined troops of European nations. The "Middle Kingdom" is China proper, but the "Son of Heaven" also rules over four dependencies, Eastern Turkestan, Mongolia, Manchuria, and Tibet. The area of the Chinese Empire altogether is thirty-five times that of the British Isles, and its population is ten times as numerous, being about 433 millions; indeed, every third or fourth man in the world is a Chinaman.