As he disappeared, he kept speaking. The effect of that undiminished voice, calm, slow, resonant, issuing from that disintegrating vapor, stirred the hair on the captive Frenchman's neck and scalp. "Vibration, _mon cher monsieur_," said he, "is everything. According to the researches of the Ecole Polytechnique, in Paris--no doubt you, yourself, have studied there, _n'est-ce pas?_--vibration of the first octave from 2 to 8 per second, give us no sense-impression. From the fourth to the fifteenth octave, 16 to 32,768 per second, we get sound. The qualities of the 16th to the 24th are--or have been, until I investigated--quite unknown. The 25th to the 35th, 33, 554, 432 to 34, 859, 738, 868 vibrations per second, give us electricity. Thence to the 45th, again unknown. "The 4th to the 48th give us heat. The 49th gives light The 50th, chemical rays, vibrating 1, 125, 899, 906, 842, 624 per second. The 51st to the 57th have never been touched by anyone save myself. The X-ray group extends from the 58th to the 61st octave. The 62d, with 4, 611, 686, 427, 889, 904 vibrations per second, is a field where only I have worked. And beyond these, no doubt, other octaves extend with infinite possibilities. "You will note, _monsieur_," he continued, while the dun penumbra still more and more withdrew him from Leclair's sight, "that great lacunae exist in the scale of vibratory phenomena. Some of the so-called lower animals take cognizance of vibrations that mean nothing to us. Insects hear notes far above our dull ears. Ants are susceptible to lights and colors unseen to our limited eyes. The emperor-moth calls its mate--so says Fabre--by means of olfactory vibrations totally uncomprehended by us. The universe is full of hues, tones, radiant phenomena that escape us, because our senses are not attuned to them." Steadily he spoke, and steadily the humming drone that filled the cabin kept its undertones that lulled, that soothed. The Frenchman, staring, hardly breathed. Rigid he sat and pale, with sweat now slowly guttering down his face, his jaws clamped hard and white. "If the true nature of the universe could suddenly be revealed to our senses," went on the Master, now hardly more than a dull blur, "we could not survive. The crash of cosmic sound, the blaze of strange lights, the hurricane forces of tempestuous energies sweeping space would blind, deafen, shrivel, annihilate us like so many flies swept into a furnace. Nature has been kind; she has surrounded us with natural ray-filters of protection." His voice now seemed issuing from a kind of vacancy. Save for a slight darkening of the air, nothing was visible of him. He went on: