'I agree with you; things probably were more fortunate. But Tsin was not without his troubles; his kingdom was for ever being invaded by Mongolian nomads from the north, nomads who were as elusive as they were warlike. They devastated portions of his kingdom, and when armies were sent in pursuit they melted away, taken in ambush, or lost hopelessly in the desert. It was to check those nomads that Tsin started the Great Wall of China beside which we lie, and no doubt, once completed, it fulfilled its purpose. It will repay a visit one of these days.'
Dick and David had, as a matter of fact, already visited the huge wall, and had marvelled at its vastness. For this Great Wall of China is not merely an erection two bricks thick; it is a huge earth wall, faced with masonry, buttressed and supported everywhere, and freely supplied with fortified gates and quarters for its garrison. Fourteen hundred miles of it, stretching across the kingdom! Think of the enormous labour, think of the host required to guard its length. And to-day it is deserted, or almost so. The broad track on its summit, constructed of such a width that three carts could conveniently be driven side by side, is now no longer of service. Mongolia has ceased to send in her nomads. Perhaps the very presence of the wall has prevented them, or maybe they have become less warlike. There the wall lies, a work to rouse the admiration of modern-day people.
'And now to speak of these ruins. They are small, as I have said already,' the Professor told them, 'and since I do not expect to discover much of interest, I have decided to send you two lads forward. John Jong shall go with you, while the naval officer who spoke such excellent English has provided me with passports. It seems that his father is a mandarin, and commands the district a hundred and fifty miles north, where are located the Mongolian ruins I am so anxious to investigate. Will you go?'
Would they go? David and Dick were as eager as the Professor himself to dip into the past by investigating the ruins of the city in which Tsin had dwelled so many hundreds of years before. But a journey through China offered superior attractions; and besides, there was another city to be visited, or rather the ruins of one that had formerly existed.