The pair found themselves in a narrow rent between the two vertical faces of rock--the projections of the one accurately corresponding with the indentations of the other, and clearly demonstrating that, at some distant period of the earth's history, that mighty chasm had been suddenly torn open by a great natural convulsion awful in its intensity beyond all power of imagination. The rent was roofed in as it were by boulders which thickly hung suspended and jammed in at varying heights between the almost touching walls of the rift; and the adventurous explorers could not repress a shudder as they glanced aloft at these huge masses and thought of the consequences to themselves which would ensue should a projecting corner just then yield and suffer its parent rock to come crashing down to the bottom. Their first impulse was to beat a precipitate retreat; their second, to go forward; for at only a few yards' distance before them the rift closed altogether, except at the very bottom, where a low cavern-like fissure dimly appeared. A hasty consultation passed between them, resulting in a determination to go forward and explore the fissure. Fortunately for their purpose they had, at an early stage of their difficulties, provided themselves with a couple of stoutish pine branches--wrenched from their parent stems and hurled into the ravine perchance by some winter storm--to aid them in surmounting the difficulties of the way, and these they now determined to utilise if possible as torches. With some little difficulty the smaller ends of these brands were induced to kindle; but, once fairly ignited, they blazed up bravely, and thus provided with the necessary lights the adventurers boldly pushed forward and plunged into the recesses of the fissure. CHAPTER THIRTEEN. AT THE NORTH POLE. The opening was so low and so narrow, that for the first fifty or sixty feet the explorers were I obliged to creep forward on their hands and knees; then it widened and became gradually higher, so that by the time they had penetrated a couple of hundred feet they were able to resume a perpendicular attitude. The cavern, if such it could be called, still however remained so narrow that it was only here and there possible for them to walk side by side. It was also very tortuous; and the heights varied momentarily, at one time compelling them to stoop almost double in order to pass beneath some immense projection, and anon increasing so greatly that the light of their torches failed to reach and reveal the roof. They observed several rifts or crevices to the right and left of them as they pressed forward, but, with one or two exceptions, these were quite impassable, and those which were not so were still so cramped that they offered no inducement to deviate from the main passage.