"Yes, yes, yes," cried the professor, putting on his fez again, and making a vicious dab at the tassel, which was tickling his neck, but subsided quietly between his shoulders after it had done swinging. "He has something to say to everything. Too much talk. It wouldn't do. The Baggara are as keen as their swords: they'd see through it directly." "Then I'd dye it blacker," said Frank. "Oh, the colour would be right enough, boy," cried the professor, "but that's what would let the cat out of the bag." "What do you mean?" "That tongue of yours, my lad. Your speech would betray you directly." "Oh, no, it would not," said Frank. "Mutes are common enough in the East, are they not?" "Oh, yes, but--" "Well, I would not talk." "Pooh!" cried the professor contemptuously. "You wouldn't talk? Why, you've got a tongue as long as a girl's. You not talk? Why, you'd be sure to burst out with something in plain English just when our lives were depending upon your silence." "_Urrr_!" growled the young fellow angrily. "Give me credit for a little more common-sense. Do you think, with the success of our expedition and poor Hal's life and happiness at stake, I couldn't make a vow to preserve silence for so many months, and keep it?" "I do think so," said the professor, clapping one hand down upon the other. "You would find it impossible. What do you say, Bob?" "Humph!" grunted the doctor. "Come, there's no need for you to hold your tongue," cried the professor petulantly. "Say something." "Very well, I'll say something," replied the doctor: "I don't know." "Yes, you do. You know it's impossible." "No," said the doctor thoughtfully; "I know it would be very hard, but seeing what a stubborn, determined fellow Frank is, I should not be surprised if he succeeded." "Hurrah!" cried Frank. "There, Landon." "Bob ought to know better," cried the professor. "It's impossible-- that's impossible--the whole business is impossible. Can't be done." "Well, I don't know," said the doctor, taking both hands to his beard and stroking and spreading it out over his breast, where it lay in crisp curls, glistening with many lights and giving him a very noble and venerable aspect. "I'm beginning to like that idea of going as a learned physician." "Oh, yes, that's right enough," said the professor. "There's no imposition there. The Arabs would have nothing to find out, and their suspicions would be allayed at once. Then, too, you could humbug them grandly with a few of your modern doctors' tools--one of those double-barrelled stethoscopes, for instance; or a clinical thermometer." "To be sure," cried Frank. "Modern Magic--good medicine for the unbelieving savages. An electric battery, too; and look here, both of you: the Rontgen rays."