"Use your imagination. He blasts out a hole by condensing the rock to a pinch of yellow powder. He moves forward into the hole he has made. I come along and reverse his process. The yellow powder expands to its original volume and the hole he has made ceases to exist. What must happen to the foreign body which had been introduced into the hole that is no longer a hole?" Carnes whistled. "At any rate, I hope that I am never in a hole when that happens." "And I devoutly hope that Saranoff is. I met with one difficulty. My ray will not penetrate the depth of solid rock which separates his borer from the surface." "Then how will you reach him to crush him? You don't expect to drill down ahead of him?" "That is my stroke of genius, Carnes. I am going to make him bore the hole down which my ray will travel to accomplish his destruction. The cathode ray and rays of that type--" * * * * * "Pardon me, Doctor," interrupted the radio operator. "I have just received a message from the squadron leader of the planes patrolling the bay. He states that every inch of the Chesapeake Bay and the Potomac River have been examined and no submarine is visible." "I expected that. He will have opened a cavern under the earth, in which his craft is safe from aerial observation. Once the borer has left it, it is invulnerable no longer." "What reply shall I make?" "Tell him to keep up a constant patrol. Three navy subs with radite-charged torpedos are on their way up the bay, together with half a dozen destroyers. The subs will scout for such a hole as I have described and will attack his sub if they find it. The destroyers will stand by and support them." The operator turned to his instrument. The electroscope observer claimed the doctor's attention. "There is a steady leak here, Doctor," he said. "I get a discharge in eleven minutes." "Probably a result of his work in opening the hiding place for his submarine last night. Keep it charged, Jones." "What did you say about the cathode ray, Doctor?" asked Carnes. "The cathode ray? Oh, yes. I said that rays of that type were attracted by--Hello, look there!" From a point a mile to the north a ball of red fire streaked up into the air. A moment later similar signals rose from other watchers in the line. "It works, Carnes!" cried the doctor as he rushed for the car. "We've got him this time!" * * * * * The car raced along the road. At the first man who had signalled, it slackened speed. The doctor leaned out. "What is your discharge rate?" he called. "Eight minutes. Doctor." The car rolled on. Dr. Bird repeated the question at the next post and was told that the electroscope there was losing its charge in seven minutes. The next man reported four minutes and the next man, one minute. The following station reported three minutes.