"Here is a map of the Eastern States," said he. "I have drawn a circle on it with a two-hundred-miles radius. At this moment a private instrument with a full crew to string sending and receiving wires is two hundred miles from here on the New York Central Railroad. It has for its transportation a private train, and it will be given a clear right of way." He turned to Simmons. "Have you found yourself able to communicate with this Monsieur X at any time?" "Communicate!" echoed Simmons. "Why, he's easier to talk to than a girl who wants an ice-cream soda!" "Then send this: 'Your messages have been communicated to the people. Be patient.'" Simmons touched the key. The spark leaped crashing. "What do you get?" asked Eldridge, after a moment. "Oh, a lot of the same sort of dope," answered Simmons wearily. "Do you want it?" "No, it is not necessary," replied Eldridge. "But listen for another message from about the same distance when he has finished." Silence fell on the room. At the end of ten minutes Simmons raised his head. "I get 'O K Q' over and over," said he. "Want that?" "That," replied Eldridge with satisfaction, "indicates that my crew on the special train in the Adirondacks two hundred miles away has heard your message to Monsieur X." He glanced at his watch. "Now, if you would be so good as to afford me a moment's assistance," he requested Simmons, "I wish to disconnect from your battery one of your powerful Leyden jars, and to substitute for it one of weaker voltage. I ventured to instruct my delivery man to leave a few in the outer hall." "That will weaken the sending power of my instrument," objected Simmons. "Exactly what I wish to do," replied Eldridge. "He's clever all right," Darrow murmured admiringly to Jack. "See what he's up to?" "Not yet," muttered Jack. The substitution completed, Eldridge again glanced at his watch. "Now," he instructed Simmons, "send the letters 'Q E D,' and continue to do so until you again hear the letters 'O K Q.'" Simmons set himself to the task. It was a long one. At last he reported his answer. "He sends 'O K Q ten,'" he said. Eldridge turned to the reporters. "That means that the substitution of the smaller Leyden jar for one of the larger reduced the sending power of this instrument just ten miles," said he. "My crew has quite simply moved slowly forward until it caught our sending here." "Next," he instructed Simmons, "see if you can communicate with Monsieur X." The operator speedily reported his success at that. Eldridge removed his glasses and polished their lenses. "Thus, gentlemen," said he, "from our circle of two-hundred-mile radius we have eliminated a strip ten miles wide. Naturally if this weakened sending reaches only one hundred and ninety miles, and our antagonist receives our messages, he must be nearer than one hundred and ninety miles. We will now further reduce the strength of our sending and try again." The younger men present broke into a shout,