Doctor Wood. Modern Wizard of the Laboratory: The Story of an American Small Boy Who Became the Most Daring and Original Experimental Physicist of Our Day-but Never Grew Up

There were four or five small pieces which had evidently formed part of a short length of steel tubing about % of an inch in diameter. They had been smashed flat by the explosion, but there was no question about their having formed a tube. The Bureau of Standards had sawed the original fragment into pieces and had pried one of them open after making a longitudinal cut with a saw. This opened section showed on the inside a number of spiral grooves, together with some small U-shaped pieces of steel wire. Close examination of these small bent fragments of wire, which might have been chain, convinced me of a totally different explanation and gave me my first clue to the real nature of the firing mechanism. I discovered, fitting them together end to end, that they must have originally come, not from a chain at all, but from a single continuous piece of steel wire, coiled inside the tube in the form of a spring. The force of the explosion had flattened the tube and broken the coiled spring into small fragments. I became completely certain of this when I discovered that the spring, pressed against the wall when the tube had been flattened by the explosion, had left a spiral groove around the inside of the tube. Though the spring had been smashed to pieces, it had left its “finger prints”.

In addition, there were a number of short fragments of a steel cylinder, exactly the same diameter as the inside of the steel tubing, and on the end of one of these were the remains of a small disk of copper, firmly welded to it or “soldered to it for some purpose unknown”, as the Bureau of Standards had reported. Prying it off I found a coating of a bright silvery metal on its back which resembled solder but which a magnet showed to be steel. It seemed probable that it was the remainder of a copper percussion cap that had been welded to the steel by the force of the explosion. The position of certain holes which had been drilled through the tube wall and also through one of the cylindrical fragments finally enabled me to reconstruct the firing mechanism which had exploded the dynamite, so I sent for the detectives and phoned the District Attorney’s office. District Attorney Parran, from Upper Marlboro County, and Wilson Ryan, a Washington criminal lawyer, who had been assigned by Governor Ritchie to assist the District Attorney, together with Lieutenant Itzel, all arrived together.

“Well”, they said, “have you found anything?”

“Yes”, I replied, “this is it”.

I took a piece of paper and drew a diagram of a short steel tube containing a spiral spring compressed by the cylinder carrying the percussion cap which was held back by a nail through the two holes in the tube and through the hole in the steel cylinder. At the other end of the tube was another short steel cylinder, also held in place by a nail. A string was tied to the nail, which held the cylinder carrying the percussion cap against the compressed spring; the other end of the string was attached to the lid of the candy box, so that when the box was opened, the nail was withdrawn, the released spring drove the cylinder with its percussion cap against the other cylinder, exploding the detonator that fired the dynamite.

They looked at the diagram in amazement. “Why”, said the District Attorney, “that’s exactly the mechanism of the rabbit gun”.

“What’s a rabbit gun?” I asked.

“A rabbit gun is a small brass twenty-two-caliber rifle attached to a log by a screw. The bait is carried on a wire attached to the trigger, the bait being in front of the muzzle, and when the rabbit takes the bait, the gun is fired and hits the rabbit in the head. But what makes your discovery exciting is this. We have evidence that Leroy Brady was taking one of these guns apart on his bench about two weeks before the murder”.

“Did you ask him why he had been doing that?”

“Yes”, they answered. “Leroy said he was taking it apart to remove the steel trigger and replace it with a brass one, because he was afraid the steel trigger would rust, out in the woods”.

“That’s nonsense”, I said. “Any good mechanic would know that a brass trigger wouldn’t work. The sharp, nicked edge which holds back the cocked hammer would wear away in no time with soft metal like brass”.