The work on the chimney had been perforce interrupted for several days, much to Beresford's benefit. The less prolonged exposure to the noxious atmosphere of the inner cave, and the new hope engendered in his heart by the knowledge that something was in progress above, effected a decided improvement in his physical and mental condition. His fear now was that he would be summoned again to the Old Man, and condemned without reprieve, before the chimney was complete. He resolved, if he were sent for, to persist in his refusal to translate the tablet, in the hope that the Old Man would spare him for yet further coercion.

Forrester set to work on the ladder as soon as possible after the knife came to hand. At night, in the passage, he cut short lengths of bamboo as rungs, and knotted them firmly to the two uprights with the cord. It was a crazy structure at the best, and he had a nervous dread lest, if he fell, he should break through or displace the slab over the pit, and be turned instantly to dust. But an experimental ascent against the wall and the cavern somewhat reassured him as to the ladder's stability, and setting its top in the cavity above the pit, he mounted and resumed the work of scouring away the dust overhead.

From that moment they applied themselves to the task with unremitting energy. As soon as their fellow prisoners were torpid in the heavy sleep that was the only alleviation of their lot, the Englishmen stole from their place, and laboured until their endurance gave out. Forrester spared Beresford as much as possible, and often undertook the double work, alternately lifting the slab to release the rays, and, when it was lowered, climbing to remove the dust. Each knew he carried his life in his hands, for the ladder could not be entirely hidden. If any priest should chance to visit by day the passage in which they laid it, he could not fail to observe it, and then their fate was sealed. But, judging by past experience, that risk was slight; and to disregard it was the only way to success.

Every now and then Forrester reported progress to his friends above. The length of the chimney increased about eighteen inches a day on the average; if, as they had calculated, there remained--before they constructed the ladder--twenty feet of rock to pierce, in a fortnight they should arrive at or very near the surface. Meanwhile they received no news of what was happening above ground. Mackenzie did not reveal his plans; perhaps, they thought, he had formed none, but was biding his time until the chimney was nearly completed. His messages were brief words of encouragement, assurances that all was well, and the news that he was in touch daily with Jackson, Sher Jang, and Hamid Gul.

Rather more than a week after the first use of the ladder, Forrester made the alarming discovery that he could no longer reach the top of the cavity with the outstretched pole. This threatened the stoppage of the work, for neither pole nor ladder could be lengthened. He did not mention the matter to Beresford, who by this time had ceased to work on the chimney. When he had transmuted the due number of plates, he was too much fatigued to endure the strain any longer, and Forrester persuaded him that he must conserve his strength for what might ensue when the chimney was completely pierced. Anything that might throw him back was to be avoided.

Forrester puzzled over the baffling problem that now confronted him. Time and again he stood looking up into the cavity, trying to conceive of a means by which the top might be reached. It was two days before he hit upon a possible solution. If he could cut notches in the walls of the chimney, and insert in them cross-bars of bamboo, he would be able to raise himself successively to heights from which the rock above would be within reach of the pole. To obtain material for the cross-bars he would have to shorten the pole; the difficulty was the notches: how could they be cut with no tool but a knife? Standing on the ladder, he tried the point of the blade on the rock, and found that this, while not very hard, was not friable enough to be excavated by so pliant a tool.

His thoughts turned at once to Mackenzie: perhaps he could find a more serviceable instrument. That night he placed in the bone the following note: "Work stopped: send a chisel." Next night he found in the bottom of the cleft, not a chisel, but a bar of iron slightly pointed at one end. Accompanying it was a note: "Hope this will serve. Let me know when near surface."

This implement he found to answer his purpose sufficiently well. From his perch on the top rung of the ladder he worked out two holes in the rock on opposite sides of the chimney; then with the knife he cut the proper length of bamboo, and thus fashioned a cross-bar on which he could stand to repeat the same operation higher up. In this way he made a series of steps enabling him to brush the dust, as before, from the top of the cavity after each employment of the rays. Only then did he acquaint Beresford with the difficulty and the manner in which it had been overcome.

The progress of the work was necessarily slower now. The cross-bars had to be removed after each ascent; otherwise at the next opening of the pit they would have been instantly destroyed. But the piercing went on steadily, and Forrester felt sure that, unless his calculations were very much out, his pole would in a few more days penetrate the roof of the chimney, and emerge through a hole in the floor of whatever room was immediately above him.

"Be very cautious," Beresford urged, when he learnt this good news. "To break through prematurely might be fatal to us all. Tell Mackenzie how things are, and ask for instructions."