No sooner had the siren blast stopped, than he had seen Alice at the Telephot, signalling him that everything was in readiness. He yelled to her to insulate herself, and he saw her jump into a tall glass chair where she sat perfectly still, deathly white. He could see that she clasped her hands to her ears; and he knew that she must be trying to shut out the thunder of the descending avalanche. He ran up his high glass ladder; and having reached the top, began to turn the large glass wheel the shaft of which was connected with the ultra-generator. As he started turning the wheel, for the first time he looked at the clock. He observed that it was just nine minutes after he first had heard the gong and he smiled, coldly. He knew he was in time. A terrifying roar set in as soon as he had commenced to turn the wheel. It was as if a million devils had been let loose. Sparks were flying everywhere. Small metal parts not encased in lead boxes fused. Long streamers of blue flames emanated from sharp objects, while ball-shaped objects glowed with a white aureole. Large iron pieces became strongly magnetic, and small iron objects continually flew from one large iron piece to another. Ralph's watch chain became so hot that he had to discard it, together with his watch. He kept on turning the wheel, and the roar changed to a scream so intense that he had to pull out his rubber ear vacuum-caps so that he might not hear the terrible sound. As he turned the wheel farther around the tone of the ultra-generator reached the note where it coincided with the fundamental note of the building, which was built of steelonium (the new substitute for steel). Suddenly the whole building "sang," with a shriek so loud and piercing that it could be heard twenty miles away. Another building whose fundamental note was the same began to "sing" in its turn, just as one tuning fork produces sympathetic sounds in a similar distant one. A few more turns of the wheel and the "singing" stopped. As he continued turning the wheel of the generator, the latter gave out sounds sharper and sharper, higher and higher, shriller and shriller, till the shrieking became unendurable. And then, suddenly, all sound stopped abruptly. _The frequency had passed over twenty thousand, at which point the human ear ceases to hear sounds._ Ralph turned the wheel a few more notches and then stopped. Except for the flying iron pieces, there was no sound. Even the myriads of sparks leaping around were strangely silent, except for the hissing noise of flames streaming from sharp metal points. Ralph looked at the clock. It was exactly ten minutes after the first sounding of the gong. He then turned the wheel one notch further and instantly the room was plunged into pitch-black darkness. * * * * *