He went back to Siberia, where he found Tug and Paul, faces still tear-streaked, staring at something that looked like a small piece of wire.
"This is it, Uncle Ralph," Tug said, brokenly. "Don't see how it could be, but it is."
"What is what?" Kinnison demanded.
"Firing pin. Brittle. When you pull the safety, the force of the spring must break it off at this constricted section here."
"But damn it, Tug, it doesn't make sense. It's tension ... but wait—there'd be some horizontal component, at that. But they'd have to be brittle as glass."
"I know it. It doesn't seem to make much sense. But we were there, you know—and I assembled every one of those God damned mines myself. Nothing else could possibly have made that mine go off just when it did."
"O.K., Tug. We'll test 'em. Call Bart in—he can have the scale-lab boys rig us up a gadget by the time we can get some more of those pins in off the line."
They tested a hundred, under the normal tension of the spring, and three of them broke. They tested another hundred. Five broke. They stared at each other.
"That's it." Kinnison declared. "But this will stink to high Heaven—have Inspection break out a new lot and we'll test a thousand."
Of that thousand pins, thirty two broke.