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

The fragment of copper removed from the body did not resemble in the slightest degree any portion of the detonator. Here was a pear-shaped pellet of solid copper the size of a small grape seed, surrounded by a thin disk of the metal which hung down from the waist of the pear like a petticoat, while a detonator is a thin-walled tube of copper about the size of a twenty-two cartridge, and from an inch to two inches in length. At the lower end there is a dent in the copper which resembles the dent made in the cap of a shotgun shell after it has been struck by the firing pin. This dent plays a curious role and gives the detonator its deadly quality, as will be seen presently. It is filled with mercury fulminate, a very high explosive, and fired by an electric current through two wires.

We suspended a detonator above a block of hard oak about five inches square and fired it. A small hole was visible in the surface of the wood, and on splitting the block we found a small pellet of copper which had penetrated the oak to a depth of about four inches. The fragment was about the size of the one taken out of the body, but it had been considerably distorted by its passage through the hard wood. I accordingly secured a few more detonators and brought them back to my laboratory where I suspended one about two feet above a large earthenware jar holding about five gallons of water, pointing the head downwards. On firing the detonator the jar was shattered into a dozen or more pieces by the pressure wave exerted in the water by the passage of the small copper fragment (the head of the detonator) entering the water with three times the velocity of a rifle bullet, just as a milk can filled with water is burst open when the bullet of a high-powered rifle is fired through it. The minute fragment of copper which was found in the ruins of the jar matched perfectly the fragment found during the autopsy but bore no resemblance to the original head of the detonator.

As further examination of detonators showed that they contained nothing of the nature of this solid bullet, it was clear that it had been molded by the heat and pressure of the explosion from the paper-thin wall of the copper detonator tube. This discovery, for it really was a discovery, shows the importance of experiment in any investigation. Up to this time the formation of this solid pellet had never been noticed or described. Its formation resulted from the presence of the dent at the bottom of the copper tube, which the explosive experts had found increased the force of the dynamite exploded by the detonator without knowing why. The reason was now quite clear. The copper bullet traverses the entire length of the dynamite stick, with an initial velocity three times that of a rifle bullet. If there were only the thin fragments of sheet copper into which the rest of the detonator is blown the explosion would be started only at one end of the stick.

The problem of how this solid pellet was formed was solved by firing detonators loaded with different amounts of explosives into a long cylindrical pasteboard tube filled with cotton, diaphragmed with thin paper disks every two inches, the pellet being searched for in the cotton lying between the last disk perforated and the next intact disk. As the pellet, which starts off with an initial velocity of about 6,000 feet per second, penetrates the cotton it gathers a tightly wadded ball around it as it advances, spinning its own cocoon, so to speak, and is thus protected from friction against the matter through which it is passing.

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Until Dr. Wood made these discoveries, not even the technical experts on dynamite, blasting, and commercial explosives had ever known or dreamed of the terrific velocity this “pellet” expelled from the detonator possessed, much less the weird, sinister shape into which it became transformed.

These detonators, harmless-looking as an ordinary small cartridge, yet as deadly dangerous as rattlesnakes — often picked up by children around quarries — began to interest Dr. Wood. He learned that there are between three hundred and four hundred accidents from detonators per year in the United States, many of them fatal. He continued his experiments and issued warnings, which have already begun to cut down this category of accidents in which children are frequently injured, mutilated, blinded, and have in some cases lost their lives.

Said Dr. Wood: “Children fire them usually by putting them on a rock and striking them with a hammer or another stone. Parents and schoolteachers should warn children that if they ever find anything resembling a twenty-two-rifle cartridge with wires or a fuse protruding from it, they should give it a wide berth and should on no account attempt to explode it”.