There was no doubt that the Professor with all his experience was also of the same opinion; for no sooner was the camp completely pitched—as they had arrived late on the previous evening they had not been able to complete the matter—than he set Ho Hung and his comrades to work.

'I imagine we must be very adjacent to the site chosen by your father, David,' he said. 'The prevailing wind is from the north-east, as one can tell at once by inspecting the cant of the few trees there are. Also, all the sand-dunes, of which there are so many, are heaped with their steep sides to leeward, and present a smooth, evenly-rounded surface to the prevailing wind. As you can see for yourself, we have the ruins between us and the wind, and so have shelter. Also, there is a stream near at hand. But this snow is not to be ignored. Ho Hung and his fellows will dig us a chamber somewhere in the ruins, where we can hide away and be warm. Once it is finished and furnished, and all other matters are seen to, we will set about getting helpers, for even small excavations demand a large amount of labour.'

That day and the three which followed were, indeed, very busy ones, so much so that few of the party wore their coats, strenuous effort being necessary, and even in that cold blast a coat was a hindrance. David and Dick themselves went in search of fire-wood, and with the help of axes cut down a number of fair-sized trees. These were lopped of their branches, placed side by side with the branches on them, and faggots on top all, then the whole was hauled close to the ruins by a team of ponies harnessed to ropes. That done, the trunks and branches were sawn in shorter lengths, and the big pieces split with wedges and a big mallet.

'We shall want every log you can cut,' said the Professor, looking his approval, 'and it is essential to make the most of the open weather. You have seen for yourselves that snow has been threatening. We shall get it any time now, and then there will be little moving around.'

Meanwhile, Ho Hung and his comrades had delved deeply. They had hit upon a spot where close investigation proved that others had been at work, though the fierce winds, which had blown since, had covered up almost all traces. Yet it was certain that a considerable amount of debris had been removed; and thanks to that fact the base of the actual ruins were soon reached.

'Might have been your father who had his men working at this spot,' said the Professor thoughtfully. 'On the other hand, it may have been a band of nomads wintering here. It is a wild district, very sparsely inhabited, and droves of men do ride here and there, not always with the best intentions I fear. However, with the half-dozen soldiers Twang Chun was good enough to lend us, we should be secure, for he has seen that the men are really trained, and I think we can rely upon their courage.'

David never knew whether to admire the huge expanse of ruins, to which they had come, more when a wintry sun poured down upon them, or when the moon's cold beams swept softly over them. In any case, there was something fascinating and awe-inspiring about this lonely place. Standing on a huge sand-dune a few hundred yards from the edge of what had once been a big city, he would allow his mind free play at times, trying to imagine the place as it was when tenanted, when its broad streets hummed with human activity, when its battlemented walls frowned down upon all would-be intruders, and when its dwellings sheltered thousands of families long since gone and forgotten. And always his eyes would wander to the relics of a tower, once a stately edifice no doubt, which even now, thousands of years after the chimneys of the city had grown cold and the streets had reverberated for the last time to the tread of inhabitants, was decidedly impressive. It seemed to beckon to him, to attract him strangely, as perhaps it had done his father. Once, since his arrival there, he had found his way across the ruins to that tower; for the feat was not impossible. Clambering up what appeared to be a breach in the rotting outer walls of the city—and who could say, since no history existed to tell of the doings in this part so long ago, that very breach might have been the undoing of the city? It may have given entry to a besieging army, and have resulted in the sacking and desolation of the place. David clambered over the sand swept into the breach and toiled over a sandy waste now piled into high pinnacles, and then drooping suddenly in a long line, where, no doubt, a street ran. Finding a way across this and others he at length arrived at a point within hailing distance of the tower. But to approach closer was impossible. A deep ditch surrounded it, with steeply sloping walls of soft sand, while on the far side a battlemented wall arose, tottering in parts, but strong and defiant in other directions.

'Just the place I should go for,' he declared when discussing the matter with the Professor. 'Should think it was the palace, and if it was, then one would imagine relics to be more abundant in such a place.'

'Precisely! And it is for that tower that I shall aim,' answered the leader of the party. 'But observe, the approach from any point outside is most difficult. To dig our way there, is almost out of the question, seeing that we have only a few months to spare in the effort. So that we must win our way by other methods, which you will see and understand when we begin to work seriously. And now, David, I have a task for you. Take two of the soldiers and Jong, and investigate the country north of us. I wish you to locate the nearest village, and make arrangements for a supply of labourers, also to discover the nearest point at which we can buy supplies, for that is more necessary even than to arrange for labour. If you take a couple of tents with you and two spare ponies you should be able to fare comfortably, and I needn't say that the sooner you are back with us the better.'

David seized upon the opportunity of a private expedition with avidity, for he had found something particularly attractive about a journey in this wild country. Carefully selecting sufficient stores and weapons, since one never knew what might happen, he set out with Jong and two of the Chinese soldiers, each of whom led a pony laden with a tent and abundance of warm coverings. Hastily swallowing his breakfast he was away almost before the sun was up, and at once rode off in a northerly direction.