Everybody agreed that Herman was too dumb to have done it.
“Now if it had been his brother… if it had been Leroy”, said farmers, gossiping around the stove in the general store at Seat Pleasant. “And what about his brother?” the police were soon inquiring. Well, Leroy Brady was the opposite of Herman, they said. Just one of those differences that happen in so many families. Leroy was a sort of mechanical genius. But he was out of the picture. He worked, and lived, in Washington, had a good-looking young wife of his own, saw little of his mother and Herman — probably hadn’t even known Naomi Hall at all. Leroy worked in a big Chevrolet garage — headquarters of the Chevrolet in Washington — and was one of the best mechanics they had. He was known to have displayed great ingenuity in devising mechanical contraptions, including a device for the opening and closing of doors.
The police weren’t quite so sure, when they looked into it, that Leroy was “out of the picture”. Yet they could discover no earthly connection or reason for Leroy Brady to have murdered Naomi Hall — except as a farfetched “favor” to his brother — and what had been learned up to then by examination and analysis of the bomb debris and fragments held nothing which pointed to their having come from any garage, much less any particular one. Steel fragments picked up in the bomb crater had been sent to the Bureau of Standards and the Bureau of Mines. The government experts’ conclusions were that the firing mechanism had been roughly similar to that which creates the spark in an ordinary cigarette lighter, and that this had been attached by a tiny chain (passing through a tube) to the lid of the box. The explosive material, they believed, might have been acetylene. In moistening one of the fragments which had a white deposit on it, they had discerned an acetylene odor. (Acetylene was already long outmoded in 1930 for motor headlights, and pointed no longer particularly to a garage as it might have in the old first days of the Model T.)
The detectives had nothing whatever on Leroy Brady beyond the fact that he had the mechanical ingenuity to have devised the bomb — and was Herman’s brother. So they were again at an impasse.
Dr. Wood, Johns Hopkins’s great experimental physicist, was called in as a police consultant on the suggestion of Governor Ritchie. The suggestion was welcomed by District Attorney Parran and the police. Dr. Wood began to work directly with Lieutenant Itzel and his department.
They handed over to me immediately (says Dr. Wood) the small steel fragments which had been found in the crater under the floor of the Hall house, and which in the meantime had been returned to them by the Bureau of Standards. Then, very sensibly, they drove me down to the scene of the explosion, which I studied thoroughly. Everything pointed to dynamite. There was a hole about eighteen inches in diameter in the kitchen table and directly below it a hole through the floor nearly three feet in diameter. I came to the conclusion that the damage could be best accounted for by about half a stick of dynamite. Acetylene, I knew, could not have done it. Then, back at Johns Hopkins, in my laboratory, I began to examine the steel fragments.
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”.