"I am very glad you brought my knapsack, Graham," said the Doctor, "as it contains my electric lamp. We will now go further into the cave, as it is important that we should know the extent of our resources when the hour of need comes."
By the light from wax tapers, burnt one after the other, we got the package undone, and soon had the lamp in working order. Its brilliant rays lit-up the cavity so well that we could see many yards before us. The Doctor led the way, lamp in hand, and following him, we climbed down deeper and deeper, and further and further, into the very bowels of the dead volcano. The cavern now began to reach an enormous size, and our light was powerless to pierce the great blackness around us, comparatively speaking, for any distance. At first the lamp illuminated the rugged walls of this ancient furnace, and the rocks, in every conceivable fantastic shape, looked grim and ghostly in the blue electric light; but as we went on and on these jagged cliffs, moulded by the molten fires of long-passed ages, gradually receded from the penetrating light, until at last the rough ground beneath us was all that was visible, and the vast immeasurable dome of the extinct crater loomed in dark weird mystery around us, our lamp but as a feeble star within its profound unknown depths. We must have travelled nearly a mile into the mountain, when we were surprised beyond measure to see the starry vault of heaven through a vast rent in the top of the cavern, thousands of feet above our heads. The crater, the entire mountain, was hollow, and the hole in the shell above us had been the vent for its now long-ago burnt-out fire! We were actually in the very core of a volcano. We proceeded but a few more steps, when the rays from our lamp revealed a vast yawning chasm before us, the light reflecting on a gulf of blackness, and not being powerful enough to illumine the furthermost edge of the pit. We shuddered as we looked at the awful abyss, and pictured to ourselves our ghastly fate if we had by some fatality walked over its terrible edge. An immense block of stone, that Graham and Sandy rolled down the steep declivity which led to the actual chasm, pitched into the blackness, and we heard it thundering down into the dizzy depths, first striking on one side, and then on the other, as it rebounded in its awful leaps like a mere pebble, the sounds echoing and re-echoing through the hollow dome around us. Then the blows sounded fainter and fainter to our ears, and finally died completely away, as if the boulder had leaped into another vaulted cavern still lower down, or been ground to dust by the force of its fall, and we heard no more!