Even as she spoke, Powell felt the narrow strip of rock under them quiver and settle. He looked quickly down. All along its length, the narrow rocky projection, weakened by their weight, was breaking swiftly away from the pit's edge. And on the floor of the pit below them the two waiting Devil Crystals moved with musical, tinkling sounds as they waited restlessly for their prey to fall among them. The horde of rat-men rallied and swept on forward in a wave that nothing could have stopped this time--but their charge was too late. The entire rocky projection collapsed with a final sickening lurch, and slid to the pit's floor, carrying Joan and Powell with it in a miniature avalanche of rocky rubble. * * * * * Even in the chaos of their wild descent, Powell retained his grip upon the loaded automatic in his hand. They struck the bottom and staggered half-dazed to their feet, to confront the two crystalline monsters rocking on their rounded bases scarcely ten feet away. The fatal cone-shaped projection was already beginning to form upon the silver-faceted side of the nearest Devil Crystal. Before the lance-like arm of crystal could flash outward, Powell sent two bullets crashing into the crystal's side just over the opalescent nucleus. The leaden missiles caromed harmlessly off, as though they had struck armor-plate, but the nucleus clouded momentarily and the cone-shaped projection dissolved back into the side. With lightning speed Powell shifted his aim to the other crystal just as its partly-formed arm was flashing toward them. His bullet crashed into the silvery side squarely over the nucleus. Again the bullet's effect was the same. This crystal nucleus clouded murkily, and the lance-like arm telescoped back into the faceted bulk. But the effect of the bullets was only momentary. Swiftly the nuclei of both crystals cleared. A deep blue film, apparently protective in nature, formed between the outer wall and each nucleus. The cones budded, and again the arms started forth. Powell fired again, and this time uselessly. His bullet struck squarely, but the shock of its impact was apparently nullified by the protective blue film. He emptied his gun in a last crashing fusillade, but without effect of any kind upon the film-guarded nuclei of the giant crystals. Their forming arms never wavered as they came lancing forward with deadly accuracy straight toward Joan and Powell. In a last effort to save Joan from the terrible doom of the crystal lances as long as possible, Powell flung his own body as a shield in front of the half-fainting girl. The tip of one of the crystalline arms struck his chest with a crashing tinkle of musical glass. Instantly the tip sprayed into a web of fine filaments that laced on around his body. A tinkling shock raced through his every nerve from the contact with the weird life force of the great crystal.