"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.
"It's right along here somewhere!" cried the doctor. "Summon everyone to this point and take up twenty-yard intervals."
From the north and south the cars came racing in. The instruments were spread out along a new line twenty yards apart. As the borer was located the intervals were decreased to fifteen feet. Dr. Bird thrust a long white rod into the ground.
"His path lies under here," he said. "Into the cars and go back a mile and test again."
The borer was making slow progress, and it was half an hour before Dr. Bird drove the second stake in the ground. With a transit he took the bearing of the path and laid it out on a large scale map.
"We'll stop him between Marr and Ritchie," he announced. "Jones, I am going back and set up my apparatus. Keep track of his movements. If he changes direction, let me know at once."
