The height of the tower as they ran the upper sections into place was forty feet. When all connections had been inspected, first by Keane, then by Philip, the former led Nukharin aloft. As the climax of his plot approached, Keane's excitement bordered on a cataleptic state, hints of which came confusedly through the conduits to Quest. With a peculiar satisfaction he felt that Keane was suffering. The inventor's jaws became rigid, as though his blood had changed to liquid air and frozen him, and he had difficulty in controlling the movements of his arms. Now he was afraid! Genuinely afraid, this time. Quest caught the impulse too clearly to doubt its meaning. This was no sham! Keane was doubting his own machine, fearing that in the crisis some element in the finely calculated mechanism might fail to operate, thus cheating him of the blood-money on which his heart was set. Then he was speaking, and even Nukharin noticed the tremor in his voice: "These nine tubes, which look like a row of gun barrels, are molded from silicon paste. Each shoots a beam of invisible light and a radio dart of precisely the same wave length. The destructive effect depends chiefly upon this exactness of synchronization." "A question occurs to me," said the Doctor: "will others be able to manipulate the machine as successfully as you can?" "It's fool-proof," chattered Keane, almost losing control of his voice, "absolutely fool-proof. Surely you have scientists in your country who can follow written directions! Nothing more is necessary." "Very well," shrugged Nukharin. "I only want to be sure that no unforeseen difficulties may arise in an emergency." "See this range-setter?" continued Keane. "The thread on the vertical shaft enables us not only to limit the range by angling the beams into the ground, but it can also be disengaged and the Projector revolved in a flat circle for maximum ranges." "And is there no danger of the machine going wrong--of destroying itself and us?" suggested Nukharin. "None whatever, Doctor. There is no explosive force and no great electrical voltage involved. As long as we stand back of the muzzles we have nothing to fear. "Now look. I have set the micrometer at three hundred yards, which will just about cover the stretch between ourselves and the lake. I will cut a swath for you--and every bush, every blade of grass, every insect in this swath will be withered to ash in the twinkling of an eye. The destruction will be absolute." "Please proceed," said Nukharin grimly. Keane pulled a lever in its slot, then pressed it down into its lock as his projection battery swung lakeward at the desired angle. Then with one hand poised on another lever, he pressed an electric button.