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

Professor Jean Perrin, Nobel laureate, now disguised as a Commandant in horizon-blue uniform with red and gold tabs, but, with his white hair and beard and perpetual good humor, looking more like Santa Claus than an officer, dashed back and forth between his laboratory and the proving ground at St.-Cyr in a military car driven at a furious pace and squeaking “toot-toot” every five seconds like a Paris taxi. He was testing his gigantic “loud-speaker” or honeycomb horn, as we called it. Hundreds and hundreds of little hexagonal horns were gathered together on a plane like the cells of honeycomb, with tubes of equal length leading to a single mouthpiece, the idea being that the sound would emerge from each trumpet at the same instant, and consequently would go off into space as a parallel beam like the rays of a searchlight. It was a terrific contraption, with its tangled network of twisted brass tubes, and did not work much better, it seemed to me, than the big ten-foot megaphone with which we used to sass the policemen two or three blocks away when I was a student at Johns Hopkins. After the armistice I tried to induce the French to present one of these to the War Museum of the Smithsonian Institution, but they wanted three thousand dollars for it!

The great flat collection of small hexagonal trumpet mouths must have been eight or ten feet in diameter. It was pointed down the field, and a narrow-gauge railway led away from it, on which operated a hand car, with two officers, armed with pens and notebooks, who recorded the distance at which they could hear speech correctly. The device was designed to enable a commander to give orders during the din of battle. How this gigantic acoustic engine on its great truck would have fared in battle seems open to question. “Gutenberg soixante-quatorze deux zéros” bellowed Perrin through the cells of the honeycomb. The observers, three hundred yards away, entered this Paris telephone number in their ledger, and drew away, pumping their hand car vigorously. “Louvre quatre-vingts soixante et un” thundered Jove again. This went on for some time, when the hand car dashed back to report observations, and I, who had been standing directly in front of the horn, told Perrin I had been learning French by a surgical operation.

Then there was Chilofski, who was experimenting with a seventy-five millimeter shell fitted with a slender rod in front, at the tip of which a flame of burning phosphorus streamed back over the shell during its flight. This was supposed to decrease the air resistance and increase the range. Since he could not fire the shells in his little laboratory from a “seventy-five”, he mounted them on the arm of a “dynagraph” and secured records of the pressure exerted by a blast of air having a velocity of 1,200 feet per second, with and without the flame. These tests showed a marked decrease in the pressure, but ballistic experts have since told me that an equal decrease could be obtained by giving the shell a long, tapering point.

The work of Professor Paul Langevin was much more promising, however. He was developing a method of locating submarines by sweeping the sea, under water, with a narrow beam of high-frequency sound waves, and picking up the “echo” reflected from the submarine by suitable electrical apparatus. As I had asked permission to devote particular attention to this work, I spent more time with Langevin than with the others. We went together to the Naval Arsenal at Toulon where the apparatus was in operation. The source of the supersonic vibrations was a system of square quartz plates properly oriented and cemented side by side to a steel disk. The quartz plates have the remarkable property of expanding and contracting when the opposite sides are put in electrical contact with the terminals of a high potential electrical generator, at the same frequency as that of the electrical oscillator. In this way sound waves of such high frequency can be caused to radiate from the steel disk that, instead of spreading out in all directions, as do audible sound waves, they are projected in a narrow beam. We saw fish die and turn belly up when they swam across the beam, and if a hand was held in the water in front of the plate, there was a painful burning sensation in the bones.

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