And the distant, muttering thunder peal, hoarse, heavy, sullen, breaking upon the sultry air, at the moment when they left the outer world, struck them as an omen--the menacing voice of outraged Nature booming the knell of those who had the temerity to seek to penetrate her innermost mysteries. CHAPTER FORTY FOUR. INFERNO. For the first forty yards the roof of the cave was so low that they had to advance in a stooping posture. Then it heightened and the tunnel widened out simultaneously. Eustace led the way, his bull's-eye lantern strapped around him, throwing a wide disk of yellow light in front. Behind him, but keeping a hand on his shoulder in order to guide him, walked Josane; the other two following in single file. A turn of the way had shut out the light from the entrance. Eustace closing the slide of the lantern for a moment, they were in black, pitchy darkness. A perceptible current of air blew into the cavern. That looked as if there should be an outlet somewhere. Old Josane, while enjoining silence upon the rest of the party, had, from the moment they had entered, struck up a low, weird, crooning song, which sounded like an incantation. Soon a glimmer of light showed just in front. "That is the other way in," muttered old Josane. "That is the way I came in. The other is the way I came out. _Hau_!" An opening now became apparent--a steep, rock shaft, reaching away into the outer air. It seemed to take one or more turnings in its upward passage, for the sky was not visible, and the light only travelled down in a dim, chastened glimmer as though it was intercepted in its course. An examination of this extraordinary feature revealed the fact that it was a kind of natural staircase. "This is the way I came in. Ha!" muttered Josane again, with a glare of resentment in his eyes as though recalling to mind some particularly ignominious treatment--as he narrowly scrutinised the slippery, rocky sides of the shaft. "I suppose it'll be the best way for us to get out," said Hoste. "Anything rather than that devil of a scramble again." "The time to talk of getting out is not yet," rejoined the Kafir drily. "We are not _in_ yet." They resumed their way. As they penetrated deeper, the cavern suddenly slanted abruptly upwards. This continued for some twenty or thirty yards, when again the floor became level, though ever with a slight upward bend. Great slabs of rock projected from the sides, but the width of the tunnel varied little, ranging between six and ten yards. The same held good of its height. As they advanced they noticed that the current of air was no longer felt. An extraordinary foetid and overpowering atmosphere had taken its place. Similarly the floor and sides of the cavern, which before they reached the outlet had been moist and humid, now became dry and firm. "Hand us your flask, Shelton," said Hoste. "Upon my soul I feel as if I was going to faint. Faugh!"