All around them the massive rock reverberated to the muffled roar of a great fire far below. Where the shelving rock floor gave into space, clouds of luminous vapors rose from out the mighty pit of the crater. Where the sun's rays beat down through it, far above them, the billowing mass was golden. Directly ahead of them it seethed in a shifting play of colors, now lurid red, now green and yellow and blue, in the reflection cast up from the flickering flames below. At times the vapor clouds were wafted aside by air currents, and Polaris could see the wall of the crater opposite, some two hundred feet across the pit. To the left the shelf of rock narrowed to a mere thread of a pathway, overhung by the bulge of the crag wall. At the right a number of low buildings of rock had been constructed along the face of the cliff. Kalin led Polaris to where the rock overhung the path, and showed him a number of footholds in the wall, by which he might climb to another small ledge above, and from which he could command a view of the platform, and also look down directly into the fearsome pit of flames. The priest then withdrew to one of the buildings. Polaris crouched at the brink of the little shelf and gazed down through the many-hued vapor clouds which were wafted by him continuously. Occasionally, when they were swept aside by drafts of air, he could see the very bottom of the crater over which he clung. It was a sight to awe the heart of the bravest. Hundreds of feet from where he crouched seethed and boiled and eddied a terrible caldron of chromatic heat. It was evident that the volcano was slowly dying, a death that might continue for centuries. Nearer to the base of the crater its circumference was greater. At its bottom, in the course of ages, the substance of the fires had cooled, forming a crust against the calcined rock walls. As the fires themselves had sunk lower they had added to the deposit of crust, leaving it in the shape of a huge funnel. In the funnel itself stewed and sweltered a lake of fire. It was nearly an acre in extent, bounded by the glowing circumference of the funnel. Its molten substance boiled and eddied in a fury of heat. Immense volumes of gas were continually belched up through it with startling detonations, spouting many feet in the air, to flame a brief instant, while the blazing masses they threw up with them fell splashing back into the fearful reek. For yards above the surface of the caldron the crust glowed a dull red. Even where the man sat the heat was withering. Voices on the rock shelf to his right drew the attention of Polaris from the broiling inferno, into which he had gazed fascinated.