"There is no need to go to that trouble, Dr. Bird," spoke a metallic voice, from nowhere, it seemed. The negroes looked at one another. Picks and shovels fell from nerveless hands.
"Your guess about a tunnel is correct, Doctor," went on the Voice. "There is a tunnel leading away from the spot where you are, but to find the end would be useless to you. I have prepared for that."
From the blacks came a low moan of fear.
"Ha'nts!" cried one of them. The cry was taken up and spread into a rolling chorus of fear. With one accord they dropped their tools and stampeded in a mad rush toward the dangling ropes. Carnes sprang forward to stop them.
"Let them go, Carnes!" cried the doctor. "Their work is done for the present. Let's locate that radio receiver."
"That also will be a useless search. Doctor," spoke up the Voice again. "I have perfected a transmitter which will send my voice through space and make it audible without the aid of the clumsy apparatus you depend on. I am also able to see you through the miles of intervening rock without the aid of any instruments at your end."
presume that you can hear me as well?"
"Certainly, Doctor. To save you trouble—and I dislike to see you waste the efforts of your really good brain on minor problems—I will tell you that your surmise is correct. A tunnel does lead both to and from the place where you stand. It twists and turns so that even you would be puzzled to plot a general direction. You would have to follow it inch by inch. If you tried that, naturally I would cause it to collapse before you, or on top of you, if you got too close. Be content with what you have seen and seek a better way to trace me."