“Ah?” said the expert, mildly interested at last; “one in the middle, you say? What is that for?”
“It is the real safety device, Stribling says; the others are merely mechanical cut-outs for the use of the wire repairers. He was explaining it to me this morning when he was connecting it in with the power wires. It’s an ordinary oil-protected switch so adjusted that in case an accident happens to a train in the tunnel the circuit will be broken automatically and the live-wire current cut out. It’s a good thing, you’d say. It would make your flesh creep to think what it would mean to have those high-power wires short-circuiting into a wreck.”
“We won’t think of it,” said the big man quizzically. “We’ll think rather of this Mr. Stribling and your—thus far—unexplained suspicions. How did he contrive to send you down here to-day?”
Benson looked up quickly.
“How did you know he sent me? I didn’t say he did, did I? But I guess that is what it amounts to. He made it a sort of personal matter; urged me to come and bring Mr. Maxwell back with me; said that on a job as big as ours he didn’t want to take any chances with his reputation as an electrical engineer or leave any room for a misunderstanding. He’d like to have Maxwell go foot by foot over the installation and see that everything is all right and safe before the power is turned on and the first electric train is sent through.”
Sprague put his face in his hands and for a few seconds the silence in the makeshift laboratory was unbroken. Then suddenly he came to life again.
“You were telling us about this internal safety device,” he broke out abruptly. “It’s an oil-switch, you say?”
“Yes; there is an iron tank to hold the oil, and——”
“Hold on; where do you find room in the tunnel for a tank?”
“In one of the side excavations. When we were driving the tunnel we left side niches every two hundred feet or so; safety-holes for the men in blasting, and places where we could store dynamite and tools out of danger and out of the way.”