Over all the chaos, the mechanical voice in the nearby tower over the laboratory droned its exhortation to the Robots. Then, suddenly, it went silent, and was followed by the human voice of Greggson. "_Robots, stop! You will end your existence! We will burn your coils! We will burn your fuses, and there will be none to replace them. Stop now!_" And again: "_Robots, come to order! You are using up your storage batteries![9] When they are exhausted, what then will you do?_" [Footnote 9: The storage batteries by which the Robot actuating energy was renewed, and the fuses, coils and other appliances necessary to the Robot existence, were all guarded now in the Power House.] In forty-eight hours, at the most, all these active Robots would have exhausted their energy supply. And if the Power House could be held in human control, the Robot activity would die. Forty-eight hours! The city, by then, would be wrecked, and nearly every human in it killed, doubtless, or driven away. * * * * * The Power House on the dam showed its lights undisturbed. The great sender there was still supplying air-power and power for the city lights. There was, too, in the Power House, an arsenal of human weapons.... The broadcaster of the Power House tower was blending his threats against the Robots with the voice of Greggson from the tower over the laboratory. Then Greggson's voice went dead; the Robots had overcome him. A Robot took his place, but the stronger Power House sender soon beat the Robot down to silence. The turmoil in the city went on. Half an hour passed. It was a chaos of confusion to Larry. He spent part of it in the official room of the palace with the harried members of the Council. Reports and blurred, televised scenes were coming in. The humans in the city were in complete rout. There was massacre everywhere. The red and violet beams were directed at the Power House now, but could not reach it. A high-voltage metal wall was around the dam. The Power House was on the dam, midway of the river channel; and from the shore end where the high wall spread out in a semi-circle there was no point of vantage from which the Robot rays could reach it. Larry left the confusion of the Council table, where the receiving instruments one by one were going dead, and went to a window nearby. Tina joined him. The mob of Robots still milled at the palace fence. One by chance was pushed against it. Larry saw the flash of sparks, the glow of white-hot metal of the Robot's body, and heard its shrill frightened scream; then it fell backward, inert. * * * * *