I took the levels roughly, and the end of it can't be far off.

Anyhow, this shaft is of no more use to us now that the Fung have found it out." Then we set to work to fill in the mouth of the passage with such loose stones as we could find.

It was a difficult business, but in the end the Mountaineers made a very fair job of it under our direction, piling the rocks in such a fashion that they could scarcely be cleared away in any short time without the aid of explosives.
While this work was going on, Japhet, Shadrach, and the Sergeant in charge of him, undertook to explore the last shaft which led down to the level of the den.

To our relief, just as we had finished building up the hole, they returned with the news that now after they had removed a fallen stone or two it was quite practicable with the aid of ropes and ladders.
So, in the same order as before, we commenced its passage, and in about half-an-hour, for it was under three hundred feet in depth, arrived safely at the foot.

Here we found a bat-haunted place like a room that evidently had been hollowed out by man.