Bob and his comrade went straight to the mayor’s office; and to that august official Fitz Mee said: “Your honor, Master Taylor wishes to go through our factories.” “So I’ve heard,” the mayor answered grimly, “but could hardly credit my ears.” Then to Bob: “Master Taylor, is this true that I hear: that you desire to go through our factories?” “Yes, sir,” Bob replied respectfully but sturdily, rather wondering, however, why such an ado should be made over so small a matter. “Very well, Fitz Mee,” said the mayor to that worthy, “I’ll depend upon you to see that Master Taylor goes through our factories; and I’ll hold you responsible for any trouble that may arise. Here’s your permit.” When the two were out of the mayor’s presence and on their way to the factories, Bob remarked: “Fitz, how did the mayor learn that I want to go through your machine-shops and places?” “He heard us talking.” “Heard us talking?” “Yes. There’s a wireless telephone instrument in the room where we were, an automatic one that catches every sound.” “Oh!” “Yes.” “And what did the mayor mean by saying he’d hold you responsible for any trouble that might arise?” “Oh, nothing—nothing!” Fitz Mee answered hastily and grumpily. The boy questioned his companion no further, and soon they crossed one of the picturesque bridges spanning the brook, ascended a long, gentle slope to the base of the black cliffs, and stood before a wide, nail-studded door. To the officers on guard Fitz Mee presented the mayor’s permit. The guard deliberately and carefully read the slip of paper, then he lifted his brows, drew down the corners of his mouth and grunted pompously: “Fitz Mee, you’re aware of the import of this official document, are you?” Fitz Mee nodded gravely, grimly, and Bob looked from one to the other in silent wonder. [Illustration: Bob and his comrade went straight to the mayor’s office.] The guard went on: “This permit of his honor, the mayor, says that not only is Master Robert Taylor, the friend and comrade of the honorable Fitz Mee, hereby permitted to go through our factories, but by the same token is _compelled_ to go through them, this being his expressed desire and pleasure; and that the honorable Fitz Mee shall be held responsible for any trouble that may thereby arise. That’s all right, is it, Fitz Mee?” [Illustration] “It’s all right,” Fitz Mee muttered sullenly, but determinedly. “Pass in,” said the officer, unbolting the door and dragging it open. As soon as the two had stepped over the sill, the door was slammed shut behind them, and Bob heard the great bolts shot into place—and shuddered in spite of himself. On each side of him were smooth, solid walls of rock: ahead of him stretched a dusky corridor dimly lighted with electric fireflies suspended here and there. The dull rumble of distant machinery came to his ears; the faint smell of smoke and sulphurous fumes greeted him. “Fitz?” the lad said to his comrade, who stood silent at his side.