“First thing I did was to scrape the surface of the safe where those scratches showed,” said Tom.
“What for?” Jimmie asked eagerly.
“It’s a well known fact,” Tom replied, “that, even if one of two metals is much harder than the other, when one scratches the other some of it comes off.
“I wanted to know whether there really was tungsten in that steel. I sent the scrapings to the laboratory. They burned it by electric arc and studied its spectrum. That’s pretty scientific,” he grinned. “There was tungsten all right. So I sent out Tungsten Tom’s pictures to several manufacturers and I got my man; that is, I proved that he had worked at the Carter Machine-Tool Company’s plant and that he did rob them.”
“How’d they catch him,” Jimmie asked.
“You’d be surprised,” Tom laughed. “He was carrying it away in his card-board lunch box. They suspected that someone was doing that so they set a powerful electro magnet beside the narrow alley-way through which all employees must leave. When Tungsten Tom’s lunch box came near it, that electro magnet smelled steel. It drew in Tungsten’s lunch box and held it fast. So that was that.”
“Pretty slick,” Jimmie smiled in admiration.
“Thanks to your aid,” the young detective went on. “We’ve got enough right now to make a good case against Tungsten. But we don’t want to spring it. We want to get his whole gang. We——”
He broke short off to stare into the street. “Can you beat that?” he exclaimed. “There’s one of those trucks now. Come on! we’ll have to follow. This may be the big hour.”
Seizing Jimmie by the arm he pushed him into a taxi and they were away.